Merge pull request #3 from LCTT/master

更新 20150308
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Chang Liu 2015-03-08 23:35:56 +08:00
commit 896e5969c5
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Flow 'N Play视频播放器有着独具风格的界面[在Ubuntu上安装]
在Ubuntu上安装Flow 'N Play—界面独具风格的视频播放器
================================================================================
**Flow N Play**是个用Qt编写的新视频播放器。它有着漂亮又简洁的界面只提供基本播放功能。
![](http://www.tuxarena.com/wp-content/uploads/2014/11/flow_n_play.jpg)
[Flow N Play][1]是个比较新的视频播放器,它有着漂亮的界面和简单的操作(今年三月份第一次发行)。其中一个功能就是能通过拖动鼠标滑动视频列表。播放器带有基本功能,一个搜索功能,支持彩色主题。
[Flow N Play][1]是个比较新的视频播放器,它有着漂亮的界面和简单的操作(2014年3月份第一次发行)。其中一个功能就是能通过拖动鼠标滑动视频列表。播放器带有基本功能,一个搜索功能,支持彩色主题。
打开一个新的视频——你还可以在同一个对话框下自定义一个封面:

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CD Audio Grabbers - Graphical Based
================================================================================
CD audio grabbers are designed to extract ("rip") the raw digital audio (in a format commonly called CDDA) from a compact disc to a file or other output. This type of software enables a user to encode the digital audio into a variety of formats, and download and upload disc info from freedb, an internet compact disc database.
Is copying CDs legal? Under US copyright law, converting an original CD to digital files for personal use has been cited as qualifying as 'fair use'. However, US copyright law does not explicitly allow or forbid making copies of a personally-owned audio CD, and case law has not yet established what specific scenarios are permitted as fair use. The copyright position is much clearer in the UK. From 2014 it become legal for UK citizens to make copies of CDs, MP3s, DVD, Blu-rays and e-books. This only applies if the individual owns the physical media being ripped, and the copy is made only for their own private use. For other countries in the European Union, member nations can allow a private copy exception too.
If you are not sure what the position is for the country you live in, please check your local copyright law to make sure that you are on the right side of the law before using the software featured in this two page article.
To some extent, it may seem a bit of a chore to rip CDs. Streaming services like Spotify and Google Play Music offer access to a huge library of music in a convenient form, and without having to rip your CD collection. However, if you already have a large CD collection, it is still desirable to be able to convert your CDs to enjoy on mobile devices like smartphones, tablets, and portable MP3 players.
This two page article highlights my favorite audio CD grabbers. I pick the best four graphical audio grabbers, and the best four console audio grabbers. All of the utilities are released under an open source license.
----------
![](http://www.linuxlinks.com/portal/content2/png/freac.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-freac.png)
fre:ac is an open source audio converter and CD ripper that supports a wide range of popular formats and encoders. The utility currently converts between MP3, MP4/M4A, WMA, Ogg Vorbis, FLAC, AAC, WAV and Bonk formats. It comes with several different presents for the LAME encoder.
#### Features include: ####
- Easy to learn and use
- Converter for MP3, MP4/M4A, WMA, Ogg Vorbis, FLAC, AAC, WAV and Bonk formats
- Integrated CD ripper with CDDB/freedb title database support
- Multi-core optimized encoders to speed up conversions on modern PCs
- Full Unicode support for tags and file names
- Easy to learn and use, still offers expert options when you need them
- Joblists
- Can use Winamp 2 input plugins
- Multilingual user interface available in 41 languages
- Website: [freac.org][1]
- Developer: Robert Kausch
- License: GNU GPL v2
- Version Number: 20141005
----------
![](http://www.linuxlinks.com/portal/content2/png/Audex.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-Audex.png)
Audex is an easy to use open source audio CD ripping application. Whilst it is in a fairly early stage of development, this KDE desktop tool is stable, slick and simple to use.
The assistant is able to create profiles for LAME, OGG Vorbis (oggenc), FLAC, FAAC (AAC/MP4) and RIFF WAVE. Beyond the assistant you can define your own profile, which means, that Audex works together with commmand line encoders in general.
#### Features include: ####
- Extract with CDDA Paranoia
- Extract and encode run parallel
- Filename editing with local and remote CDDB/FreeDB database
- Submit new entries to CDDB/FreeDB database
- Metadata correction tools like capitalize etc
- Multi-profile extraction (with one commandline-encoder per profile)
- Fetch covers from the internet and store them in the database
- Create playlists, cover and template-based-info files in target directory
- Create extraction and encoding protocols
- Transfer files to a FTP-server
- Internationalization support
- Website: [kde.maniatek.com/audex][2]
- Developer: Marco Nelles
- License: GNU GPL v3
- Version Number: 0.79
----------
![](http://www.linuxlinks.com/portal/content2/png/SoundJuicer.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-SoundJuicer.png)
Sound Juicer is a lean CD ripper using GTK+ and GStreamer. It extracts audio from CDs and converts it into audio files. Sound Juicer can also play audio tracks directly from the CD, offering a preview before ripping.
It supports any audio codec supported by a GStreamer plugin, including MP3, Ogg Vorbis, FLAC, and uncompressed PCM formats.
It is an established part of the GNOME desktop environment.
#### Features include: ####
- Automatic track tagging via CDDB
- Encoding to ogg / vorbis, FLAC and raw WAV
- Easy to configure encoding path
- Multiple genres
- Internationalization support
- Website: [burtonini.com][3]
- Developer: Ross Burton
- License: GNU GPL v2
- Version Number: 3.14
----------
![](http://www.linuxlinks.com/portal/content2/png/ripperX.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-ripperX.png)
ripperX is an open source graphical interface for ripping CD audio tracks and encoding them to Ogg, MP2, MP3, or FLAC formats. It's goal is to be easy to use, requiring only a few mouse clicks to convert an entire album. It supports CDDB lookups for album and track information.
It uses cdparanoia to convert (i.e. "rip") CD audio tracks to WAV files, and then calls the Vorbis/Ogg encoder oggenc to convert the WAV to an OGG file. It can also call flac to perform lossless compression on the WAV file, resulting in a FLAC file.
#### Features include: ####
- Very simple to use
- Rip audio CD tracks into WAV, MP3, OGG, or FLAC files
- Supports CDDB lookups
- Supports ID3v2 tags
- Pause the ripping process
- Website: [sourceforge.net/projects/ripperx][4]
- Developer: Marc André Tanner
- License: MIT/X Consortium License
- Version Number: 2.8.0
--------------------------------------------------------------------------------
via: http://www.linuxlinks.com/article/20150125043738417/AudioGrabbersGraphical.html
作者Frazer Kline
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[1]:http://www.freac.org/
[2]:http://kde.maniatek.com/audex/
[3]:http://burtonini.com/blog/computers/sound-juicer
[4]:http://sourceforge.net/projects/ripperx/

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Pinta 1.6 Released! Install It In Ubuntu And Linux Mint
================================================================================
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Pinta_Ubuntu_Linux.jpeg)
[Pinta][1] is a free and open source drawing application which is very popular among Linux users. It wont be incorrect to term it as an **open source alternative to Microsoft Paint**. Pinta is available for all major platforms such as Linux, Windows and Mac OS X.
While Gimp is popular as full featured image editing software, Pinta is more of a paint and drawing tool. I have used it extensively in my tutorials for drawing arrows and curves on the screenshots and I can say that its my favorite drawing app in Linux.
### New features in Pinta 1.6 ###
After over an year, Pinta has released version 1.6, fixing over 50 bugs and introducing some new features. New features are as following:
- Line tool now supports drawing curves and arrows
- Shapes can be edited even after being drawn
- All shape tools now support drawing dashed lines
- All selection tools now support the Union, Exclude, Xor, and Intersection modes
- Add-in manager now consists of add ins
- New options in command line usage
New version also fixes the annoying bug where you [cannot open a file with Pinta in right click menu option][2]. You can read all the changes in the [release note][3].
### Install Pinta 1.6 in Ubuntu and Linux Mint ###
Pinta 1.5 is available in Ubuntu 14.04, 14.10, Linux Mint 17, elementary OS. If you want to install the latest version 1.6, you can use the official PPA from Pinta team. Dont worry if you have Pinta 1.5 installed already. Installing it again will upgrade the version.
Open a terminal and use the following commands:
sudo add-apt-repository ppa:pinta-maintainers/pinta-stable
sudo apt-get update
sudo apt-get install pinta
To download the source code or to get the installation files for Windows and Mac OS X, check the [download page of Pinta][4]. In a related post, you can also check out [best photo applications for Linux][5].
--------------------------------------------------------------------------------
via: http://itsfoss.com/pinta-1-6-ubuntu-linux-mint/
作者:[Abhishek][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://itsfoss.com/author/abhishek/
[1]:http://pinta-project.com/
[2]:http://itsfoss.com/add-application-list-open-applications-ubuntu-1310/
[3]:http://pinta-project.com/releases/1-6
[4]:http://pinta-project.com/releases
[5]:http://itsfoss.com/image-applications-ubuntu-linux/

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theol-l translating
The Curious Case of the Disappearing Distros
================================================================================
![](http://www.linuxinsider.com/ai/828896/linux-distros.jpg)
@ -117,4 +119,4 @@ via: http://www.linuxinsider.com/story/The-Curious-Case-of-the-Disappearing-Dist
[5]:http://ledgersmbdev.blogspot.com/
[6]:http://www.ledgersmb.org/
[7]:http://www.novell.com/linux
[8]:http://www.redhat.com/
[8]:http://www.redhat.com/

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Ubuntu 15.04 Finally Lets You Set Menus To Always Show
================================================================================
**If you hate the way that Unitys global menus fade out of view after you mouse away, Ubuntu 15.04 has a little extra to win you around.**
![](http://www.omgubuntu.co.uk/wp-content/uploads/2014/02/locally-integrated-menus-in-ubuntu.png)
The latest build of Unity for Ubuntu 15.04, currently sitting in the proposed channel, offers an option to **make app menus visible in Ubuntu**.
No fading, no timeout, no missing menus.
The drawback for now is that it can currently only be enabled through a dconf switch and not a regular user-facing option.
Id hope (if not expect) that an option to set the feature is added to the Ubuntu System Settings > Appearance section as development continues.
Right now, if youre on Ubuntu 15.04 and have the “Proposed” update channel enabled, you should find this switch waiting in **com > canonical > unity >** always show menus.
### Better Late Than Never? ###
Developers plan to backport the option to Ubuntu 14.04 LTS in the next SRU (assuming nothing unexpected crops up during testing).
Locally Integrated Menus (LIM) debuted in Ubuntu 14.04 LTS to much appreciation, being widely seen as the best compromise between those who liked the simplicity of the “hidden” approach and those who disliked the mouse and trackpad aerobics using it required.
While locally integrated menus brought us half way to silencing the criticisms levelled at this aspect of Unity, the default “fade in/fade out” behaviour left an itch unscratched.
The past few releases of Ubuntu has seen proactive addressing of concerns and issues experienced by its earlier UX decisions. After several years on the to do list [we finally got Locally Integrated Menus last year][1], as well as an unsupported [option to minimise and restore apps to the Unity Launcher][2] by clicking on their icon.
A year on from that we finally get an option to make application menus always show, no matter where our mouse is. Better late than never, right?
--------------------------------------------------------------------------------
via: http://www.omgubuntu.co.uk/2015/01/ubuntu-15-04-always-show-menu-bar-option
作者:[Joey-Elijah Sneddon][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:https://plus.google.com/117485690627814051450/?rel=author
[1]:http://www.omgubuntu.co.uk/2014/02/locally-integrated-menus-ubuntu-14-04
[2]:http://www.omgubuntu.co.uk/2014/03/minimize-click-launcher-option-ubuntu-14-04

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translating by KayGuoWhu
Why does C++ promote an int to a float when a float cannot represent all int values?
---------
#Q:
Say I have the following:
```C
int i = 23;
float f = 3.14;
if (i == f) // do something
```
The i will be promoted to a float and the two float numbers will be compared, but can a float represent all int values? Why not promote both the int and the float to a double?
#A:
When `int` is promoted to `unsigned` in the integral promotions, negative values are also lost (which leads to such fun as `0u < -1` being true).
Like most mechanisms in C (that are inherited in C++), the usual arithmetic conversions should be understood in terms of hardware operations. The makers of C were very familiar with the assembly language of the machines with which they worked, and they wrote C to make immediate sense to themselves and people like themselves when writing things that would until then have been written in assembly (such as the UNIX kernel).
Now, processors, as a rule, do not have mixed-type instructions (add float to double, compare int to float, etc.) because it would be a huge waste of real estate on the wafer -- you'd have to implement as many times more opcodes as you want to support different types. That you only have instructions for "add int to int," "compare float to float", "multiply unsigned with unsigned" etc. makes the usual arithmetic conversions necessary in the first place -- they are a mapping of two types to the instruction family that makes most sense to use with them.
From the point of view of someone who's used to writing low-level machine code, if you have mixed types, the assembler instructions you're most likely to consider in the general case are those that require the least conversions. This is particularly the case with floating points, where conversions are runtime-expensive, and particularly back in the early 1970s, when C was developed, computers were slow, and when floating point calculations were done in software. This shows in the usual arithmetic conversions -- only one operand is ever converted (with the single exception of `long/unsigned int`, where the `long` may be converted to `unsigned long`, which does not require anything to be done on most machines. Perhaps not on any where the exception applies).
So, the usual arithmetic conversions are written to do what an assembly coder would do most of the time: you have two types that don't fit, convert one to the other so that it does. This is what you'd do in assembler code unless you had a specific reason to do otherwise, and to people who are used to writing assembler code and do have a specific reason to force a different conversion, explicitly requesting that conversion is natural. After all, you can simply write
```C
if((double) i < (double) f)
```
It is interesting to note in this context, by the way, that `unsigned` is higher in the hierarchy than `int`, so that comparing `int` with `unsigned` will end in an unsigned comparison (hence the `0u < -1` bit from the beginning). I suspect this to be an indicator that people in olden times considered `unsigned` less as a restriction on `int` than as an extension of its value range: We don't need the sign right now, so let's use the extra bit for a larger value range. You'd use it if you had reason to expect that an `int` would overflow -- a much bigger worry in a world of 16-bit ints.
----
via:[stackoverflow](http://stackoverflow.com/questions/28010565/why-does-c-promote-an-int-to-a-float-when-a-float-cannot-represent-all-int-val/28011249#28011249)
作者:[wintermute][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://stackoverflow.com/users/4301306/wintermute

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9 Best IDEs and Code Editors for JavaScript Users
================================================================================
Web designing and developing is one of the trending sectors in the recent times, where more and more peoples started to search for their career opportunities. But, Getting the right opportunity as a web developer or graphic designer is not just a piece of cake for everyone, It certainly requires a strong mind presence as well as right skills to find the find the right job. There are a lot of websites available today which can help you to get the right job description according to your knowledge. But still if you want to achieve something in this sector you must have some excellent skills like working with different platforms, IDEs and various other tools too.
Talking about the different platforms and IDEs used for various languages for different purposes, gone is the time when we learn just one IDE and get the optimum solutions for our web design projects easily. Today we are living in the modern lifestyle where competition is getting more and more tough on every single day. Same is the case with the IDEs, IDE is basically a powerful client application for creating and deploying applications. Today we are going to share some best javascript IDE for web designers and developers.
Please visit this list of best code editors for javascript user and share your thought with us.
### 1) [Spket][1] ###
**Spket IDE** is powerful toolkit for JavaScript and XML development. The powerful editor for JavaScript, XUL/XBL and Yahoo! Widget development. The JavaScript editor provides features like code completion, syntax highlighting and content outline that helps developers productively create efficient JavaScript code.
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/spket-e1422674329554.png)
### 2) [Ixedit][2] ###
IxEdit is a JavaScript-based interaction design tool for the web. With IxEdit, designers can practice DOM-scripting without coding to change, add, move, or transform elements dynamically on your web pages.
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/ixedit.png)
### 3) [Komodo Edit][3] ###
Komode is free and powerful code editor for Javascript and other programming languages.
![](http://i2.wp.com/devzum.com/wp-content/uploads/2015/01/komodo-edit-e1422674596277.png)
### 4) [EpicEditor][4] ###
EpicEditor is an embeddable JavaScript Markdown editor with split fullscreen editing, live previewing, automatic draft saving, offline support, and more. For developers, it offers a robust API, can be easily themed, and allows you to swap out the bundled Markdown parser with anything you throw at it.
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/epiceditor-e1422674732281.png)
### 5) [codepress][5] ###
CodePress is web-based source code editor with syntax highlighting written in JavaScript that colors text in real time while its being typed in the browser.
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/codepres-e1422674893706.png)
### 6) [ACe][6] ###
Ace is an embeddable code editor written in JavaScript. It matches the features and performance of native editors such as Sublime, Vim and TextMate. It can be easily embedded in any web page and JavaScript application.
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/ace-e1422675089912.png)
### 7) [scripted][7] ###
Scripted is a fast and lightweight code editor with an initial focus on JavaScript editing. Scripted is a browser based editor and the editor itself is served from a locally running Node.js server instance.
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/scripted-e1422675188408.png)
### 8) [Netbeans][8] ###
This is another more impressive and useful code editors for javascript and other programming languages.
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/code_editing1-e1422675506226.png)
### 9) [Webstorm][9] ###
This is the smartest ID for javascript. WebStorm is a lightweight yet powerful IDE, perfectly equipped for complex client-side development and server-side development with Node.js.
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/webstorm.png)
--------------------------------------------------------------------------------
via: http://devzum.com/2015/01/31/9-best-ides-and-code-editors-for-javascript-users/
作者:[vikas][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://devzum.com/author/vikas/
[1]:http://spket.com/
[2]:http://www.ixedit.com/
[3]:http://komodoide.com/komodo-edit/
[4]:http://oscargodson.github.io/EpicEditor/
[5]:http://codepress.sourceforge.net/
[6]:http://ace.c9.io/#nav=about
[7]:https://github.com/scripted-editor/scripted
[8]:https://netbeans.org/
[9]:http://www.jetbrains.com/webstorm/

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theo-l translating
How to Monitor Network Usage with nload in Linux
================================================================================
nload is a free linux utility that can help the linux user or sysadmin to monitor network traffic and bandwidth usage in real time by providing two simple graphs: one per incoming traffic and one for outgoing traffic.
I really like to use **nload** to display information on my screen about the current download speed, the total incoming traffic, and the average download speed. The graphs reported by nload tool are very easy to interpret and what is the most important thing they are very helpful.
According to the manual pages it monitors all network devices by default, but you can easily specify the device you want to monitor and also switch between different network devices using the arrow keys. There are many options avaliable such as -t to determine refresh interval of the display in milliseconds (the default value of interval is 500), -m to show multiple devices at the same time(traffic graphs are not shown when this option is used), -u to set the type of unit used for the display of traffic numbers and many others that we are going to explore and practise in this tutorial.
### How to install nload on your linux machine ###
**Ubuntu** and **Fedora** users can easily install nload from the default repositories.
Install nload on Ubuntu by using the following command.
sudo apt-get install nload
Install nload on Fedora by using the following command.
sudo yum install nload
What about **CentOS** users? Just type the following command on your machine and you will get nload installed.
sudo yum install nload
The following command will help you to install nload on OpenBSD systems.
sudo pkg_add -i nload
A very effective way to install software on linux machine is to compile by source as you can download and install the latest version which usually means better performance, cool features and less bugs.
### How to install nload from source ###
The first thing you need to do before installing nload from source you need to download it and to do this I like to use the wget uility which is available by default on many linux machines. This free utility helps linux users to download files from the web in a non-interactive way and has support for the following protocols.
- HTTP
- HTTPS
- FTP
Change directory to **/tmp** by using the following command.
cd /tmp
Now type the following command in your terminal to download the latest version of nload on your linux machine.
wget http://www.roland-riegel.de/nload/nload-0.7.4.tar.gz
If you don't like to use the linux wget utility you can easily download it from the [official][1] source by just a mouse click.
The download will finish in no time as it is a small software. The next step is to untar the file you downloaded with the help of the **tar** utility.
The tar archiving utility can be used to store and extract files from a tape or disk archive. There are many options available in this tool but we need the followings to perform our operation:
1. **-x** to extract files from an archive
1. **-v** to run in verbose mode
1. **-f** to specify the files
For example:
tar xvf example.tar
Now that you learned how to use the tar utility I am very sure you know how to untar .tar archives from the commandline.
tar xvf nload-0.7.4.tar.gz
Then use the cd command to change directory to nload*.
cd nload*
It looks like this on my system.
oltjano@baby:/tmp/nload-0.7.4$
Now run the command
./configure
to to configure the package for your system.
./configure
Alot of stuff is going to be displayed on your screen. The following screenshot demonstrates how it is going to look like.
![configuring packages for nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload1.png)
Then compile the nload with the following command.
make
![compiling nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload2.png)
And finally install nload on your linux machine with the following command.
sudo make install
![installing nload from source](http://blog.linoxide.com/wp-content/uploads/2015/01/nload3.png)
Now that the installation of nload is finished it is time for you to learn how to use it.
### How to use nload ###
I like to explore so type the following command on your terminal.
nload
What do you see?
I get the following.
![running nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.png)
As you can see from the above screenshot I get information on:
### Incoming Traffic ###
#### Current download speed ####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.1.png)
#### Average download speed ####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.2.png)
#### Minimum download speed ####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.3.png)
#### Maximum download speed ####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.4.png)
#### Total incoming traffic in bytes by default ####
![](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.5.png)
### Outgoing Traffic ###
The same goes for outgoing traffic.
#### Some useful options of nload ####
Use the option
-u
to set set the type of unit used for the display of traffic numbers.
The following command will help you to use the MBit/s unit.
nload -u m
The following screenshot shows the result of the above command.
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload5.png)
Try the following command and see the results.
nload -u g
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload6.png)
There is also the option **-U**. According to the manual pages it is same as the option -u but only for an amount of data. I tested this option and to be honest it very helpful when you want to check the total amount of traffic be it incoming or outgoing.
nload -U G
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload7.png)
As you can see from the above screenshot the command **nload -U G** helps to display the total amount of data (incoming or outgoing) in Gbyte.
Another useful option I like to use with nload is the option **-t**. This option is used to refresh interval of display in milliseconds which is 500 by default.
I like to experiment a little by using the following command.
nload -t 130
So what the above command does is that it sets the display to refresh every 130 milliseconds. It is recommended to no specify refresh intervals shorter than about 100 milliseconds as nload will generate reports with mistakes during the calculations.
Another option is **-a**. It is used when you want to set the length in seconds of the time window for average calculation which is 300 seconds by default.
What if you want to monitor a specific network device? It is very easy to do that, just specify the device or the list of devices you want to monitor like shown below.
nload wlan0
![nload monitoring wlan0 on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload8.png)
The following syntax can help to monitor specific multiple devices.
nload [options] device1 device2 devicen
For example use the following command to monitor eth0 and wlan0.
nload wlan0 eth0
And if you run the command nload without any option it will monitor all auto-detected devices, you can display graphs for each one of them by using the right and left arrow keys.
--------------------------------------------------------------------------------
via: http://linoxide.com/monitoring-2/monitor-network-usage-nload/
作者:[Oltjano Terpollari][a]
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[1]:http://www.roland-riegel.de/nload/nload-0.7.4.tar.gz

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Linux FAQs with Answers--How to use yum to download a RPM package without installing it
================================================================================
> **Question**: I want to download a RPM package from Red Hat's standard repositories. Can I use yum command to download a RPM package without installing it?
yum is the default package manager for Red Hat based systems, such as CentOS, Fedora or RHEL. Using yum, you can install or update a RPM package while resolving its package dependencies automatically. What if you want to download a RPM package without installing it on the system? For example, you may want to archive some RPM packages for later use or to install them on another machine.
Here is how to download a RPM package from yum repositories.
### Method One: Yum ###
The yum command itself can be used to download a RPM package. The standard yum command offers '--downloadonly' option for this purpose.
$ sudo yum install --downloadonly <package-name>
By default, a downloaded RPM package will be saved in:
/var/cache/yum/x86_64/[centos/fedora-version]/[repository]/packages
In the above, [repository] is the name of the repository (e.g., base, fedora, updates) from which the package is downloaded.
If you want to download a package to a specific directory (e.g., /tmp):
$ sudo yum install --downloadonly --downloaddir=/tmp <package-name>
Note that if a package to download has any unmet dependencies, yum will download all dependent packages as well. None of them will be installed.
One important thing is that on CentOS/RHEL 6 or earlier, you will need to install a separate yum plugin (called yum-plugin-downloadonly) to be able to use '--downloadonly' command option:
$ sudo yum install yum-plugin-downloadonly
Without this plugin, you will get the following error with yum:
Command line error: no such option: --downloadonly
![](https://farm9.staticflickr.com/8627/15571201803_38390aae75_c.jpg)
### Method Two: Yumdownloader ###
Another method to download a RPM package is via a dedicated package downloader tool called yumdownloader. This tool is part of yum-utils package which contains a suite of helper tools for yum package manager.
$ sudo yum install yum-utils
To download a RPM package:
$ sudo yumdownloader <package-name>
The downloaded package will be saved in the current directory. You need to use root privilege because yumdownloader will update package index files during downloading. Unlike yum command above, none of the dependent package(s) will be downloaded.
--------------------------------------------------------------------------------
via: http://ask.xmodulo.com/yum-download-rpm-package.html
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translating by martin.
How to Setup Passwordless SSH Logon to Ubuntu 14.04
================================================================================
Hi all, today we'll gonna learn how we can setup Passwordless SSH Logon to Ubuntu 14.04 "Trusty". Only the workstations having the correct matching key pair (private and public) will be allowed to logon to the SSH server, without the key paring, access will not be allowed.
Usually, we need to enter username and password combination to connect to an SSH console. If the combination is correct to that of the system's then, we get access to the server else we are denied from the access. But, there is something more secure than Password logon, we have passwordless SSH logon using the encrypted keys.
If you want to enable this secured option, we can simply disable password-logon and only allow logon using an encryption key. When using encryption keys option, the client computer generates a private and public key pair. The client then must upload the public key to the SSH server authorized_key file. Before access is granted, the server and client computer validate the key pair. If the public key on the server matches the private key submitted via the client then access will be granted else will be denied.
This is a very secure way authenticating to a SSH server and its a recommended method if you wish to implement secure logon with single user SSH logon. Here's a quick step-wise process on how to enable Passwordless SSH logon.
### 1. Installing Openssh Server ###
First off all, we'll need to update our local repository index. To do so, we'll first need to run apt-get update as shown below.
$ sudo apt-get update
![Updating Repo Index](http://blog.linoxide.com/wp-content/uploads/2015/02/updating-repo-list.png)
Now, we can install openssh-server by running following command.
$ sudo apt-get install openssh-server
![Installing openssh server](http://blog.linoxide.com/wp-content/uploads/2015/02/installing-openssh-server.png)
### 2. Enabling Openssh Server ###
Now, we'll want to enable OpenSSH server after we successfully installed it on our Ubuntu 14.04 Operating System. The command to enable/start the server is given as follows.
$ sudo service ssh start
OR
$ sudo /etc/init.d/ssh start
### 3. Configuring Key Pair ###
After we have installed our OpenSSH Server and enabled it. We'll now finally wanna go for generating our Public and Private Key Pair. To do that, run the following command in a terminal or console.
$ ssh-keygen -t rsa
After running the above command, we'll be prompted to complete a series of tasks. The first will be where to save the keys, press Enter to choose the default location which is in a hidden .ssh folder in the home directory. The next prompt will be to enter the Paraphrase. I personally leave this blank (just press enter) to continue. It will then create the key pair and were done.
![Generating Key Pair](http://blog.linoxide.com/wp-content/uploads/2015/02/generating-key-pair.png)
After generation of the key pair, we will need to **copy the clients public key to the SSH server** or host inorder to create trusted relationship with it. We'll need to run the commands below to copy the client public key to the server.
$ ssh-copy-id user@ip_address
After the public key is copied to the server, we can now go and disable password logon via SSH. To do that, we'll need to open **/etc/ssh/ssh_config** via a text editor by run the commands below.
$ sudo nano /etc/ssh/sshd_config
Now, we'll need to uncomment the lines and set the values as shown below.
![Configuring sshd Config](http://blog.linoxide.com/wp-content/uploads/2015/02/configuring-sshd_config.png)
### 4. Restarting the SSH Server ###
Finally, after we are done configuring SSH Server, we'll want to restart our SSH Server so that all the changes will take affect. To restart one can run the following command in a terminal or the console.
$ sudo service ssh restart
OR
$ sudo /etc/init.d/ssh restart
![Restarting ssh](http://blog.linoxide.com/wp-content/uploads/2015/02/restarting-ssh.png)
Finally, we can now ssh in to the server without a password and only from the client having the same key pair not the password.
### Conclusion ###
Hurray! We have successfully enabled Passwordless SSH logon. It is a lot secure to enable Encrypted Key Pair SSH logon . This is a very secure way authenticating to a SSH server and its a recommended method if you wish to implement secure logon with single user SSH logon. So, if you have any questions, suggestions, feedback please write them in the comment box below. Thank you ! Enjoy Encrypted Secure SSH Login :-)
--------------------------------------------------------------------------------
via: http://linoxide.com/ubuntu-how-to/setup-passwordless-ssh-logon-ubuntu-14-04/
作者:[Arun Pyasi][a]
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How To Fix “Not Enough Free Disk Space On /boot” In Ubuntu
================================================================================
### Question: How To Fix “Not Enough Free Disk Space On /boot” In Ubuntu? ###
Today, I got the following error, but a simple one, when try to update my Lubuntu 14.04 desktop.
> “Not Enough Free Disk Space On /boot”
![](https://www.unixmen.com/wp-content/uploads/2015/02/Software-Updater_002.png)
This is because my /boot partition has caught up with unwanted old kernels, packages etc.
### Answer: ###
I heard about **Computer Janitor** feature which will remove unwanted old junk files in Ubuntu Tweak tool. Using the Computer Janitor, you can clean up your system like a freshly installed system. Janitor will remove;
- Apps cache(Firefox/Chrome cache, Software center cache);
- Thumbnail cache;
- Apt cache;
- Old kernels;
- Package configs;
- And unneeded packages.
If you havent install this tool, look at the following link.
- **[How To Install And Use Ubuntu Tweak On Ubuntu][1]**
To remove unwanted junk files, open Ubuntu Tweak, and click on the **Janitor** option.
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_006.png)
Select the check the boxes to remove unwanted junk from your system, and click **Clean** button.
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_007.png)
Janitor will now start to clean up your system
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_003.png)
Cool! The system is clean now.
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_008.png)
Again I re-launched the software updater. This time it went smoothly without any issues.
![](https://www.unixmen.com/wp-content/uploads/2015/02/Software-Updater_009.png)
Thats all. Enjoy. There are others ways also available to clean up the system. But, this seems very easy to follow. We can do system clean up in few mouse clicks.
Cheers!
--------------------------------------------------------------------------------
via: https://www.unixmen.com/how-to-fix-not-enough-free-disk-space-on-boot-in-ubuntu/
作者:[SK][a]
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[1]:http://www.unixmen.com/after-a-fresh-install-of-ubuntu-1010-maverick-meerkat-configuration-made-easy-with-ubuntu-tweak/

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How To Fix Windows Updates Stuck At 0%
================================================================================
How do you feel when you log in to Windows after a month, find there are updates to install, you select to install these updates and those **Windows updates stuck at zero percent**?
Why am I talking about Windows updates on a blog dedicated to Linux and Open Source? Because I prefer to [dual boot Windows with Linux][1]. While I use Linux as my main desktop, once in a while I do log in to Windows. The most annoying thing after logging in Windows is the Windows updates. It has happened to me on several occasions that I found **Windows update not working**. I choose to install the updates and Windows updates get stuck at 0 KB and 0%, like this:
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_Updates_stuck_at_zero.jpeg)
In this tutorial, we shall see how to make Windows update work again. The tutorial should be applicable for Windows 7, Windows 8 and Windows 8.1.
### Fix Windows updates stuck at zero percent ###
Please mind that Windows updates can be stuck at any percent and the trick which we are going to use would require you to install those updates again. I hope you do not find that too inconvenient. If you are ready, lets see how to fix this Windows update issue.
#### Step 1: ####
Press Windows+R. This will prompt run dialogue box. In here, type services.msc:
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Updates_3.png)
#### Step 2: ####
Now it brings us to all the services installed in Windows. These services are listed in alphabetical order. Scroll down and look for **Windows Update Service**. Right click on it and stop it.
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_Updates_stuck_1.jpeg)
#### Step 3: ####
Now go in **C:\Windows\SoftwareDistribution and delete all of its contents**. Actually, this is the folder where downloaded installation files were stored. But since Windows update suck, they somehow have problem with partially downloaded update files.
#### Step 4: ####
Go back to services again (as mentioned in Step 1) and this time start the Windows Update Service, by right clicking on it. Try to update Windows again. It should be working this time.
So once you have got the updates working, perhaps you will find plenty of updates to install at next reboot. And that moment calls for a meme:
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_update_suck.jpg)
Jokes apart, I hope this tip helps you to get rid of Windows updates hanged at 0%. I wish that Linux like updates are also included in the list of [Windows 10 features copied from Linux][2]. I wish.
--------------------------------------------------------------------------------
via: http://itsfoss.com/fix-windows-updates-stuck-0/
作者:[Abhishek][a]
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[1]:http://itsfoss.com/install-ubuntu-1404-dual-boot-mode-windows-8-81-uefi/
[2]:http://itsfoss.com/windows-10-inspired-linux/

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Translating
Linux Basics: How To Find Maximum Supported RAM By Your System
================================================================================
![](https://1102047360.rsc.cdn77.org/wp-content/uploads/2015/02/RAM-790x527.jpg)
@ -693,4 +695,4 @@ via: https://www.unixmen.com/linux-basics-how-to-find-maximum-supported-ram-by-y
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
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[a]:https://www.unixmen.com/author/sk/

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Monitoring Your Network And Servers With Observium
================================================================================
### Introduction ###
You have a problem while monitoring your servers, switches or physical machines. **Observium** fits your need. As a free monitoring system, it helps you to monitor your servers remotely. It is an auto-discovering SNMP based network monitoring platform written in PHP which includes support for a wide range of network hardware and operating systems including Cisco, Windows, Linux, HP, NetApp and many other. I will give you the steps to follow while setting up an **Observium** server on Ubuntu 12.04.
![](https://www.unixmen.com/wp-content/uploads/2015/03/Capture1.png)
Currently there are two different versions of **observium**.
- The observium Community is a free tool and licensed under the QPL Open Source license. This version is the best solution for small deployments. It gets security updates each 6 months.
- While the second version, the Observium Professional is distributed under SVN based release mechanism. And it gets daily security updates. This tool is the best for Service Provider and enterprises deployments.
For more information you can visit the offcial [website of Observium][1].
### System Requirements ###
In order to install **Observium** , its necessary to have a server with a fresh installation. The development of **Observium** takes place on Ubuntu LTS and Debian systems, so its recommended to install **Observium** on Ubuntu or Debian because may be issues with other platforms.
This article will guide you on how to install **Observium** on Ubuntu 12.04. For a small **Observium** installation is recommended to use 256MB for the memory and dual core for the process.
### Installing Prerequisites ###
Before installing **Observium** you need to make sure to install all dependencies.
First step is to update your server
sudo apt-get update
Then you need to install all packages required to run Observium.
Observuim need this list of software the run correctly:
- LAMP server
- fping
- Net-SNMP 5.4+
- RRDtool 1.3+
- Graphviz
Requirements for optional features:
- Ipmitool Only if you want to poll IPMI baseboard controllers on servers
- Libvirt-bin Only if you want to monitor remote VM hosts using libvirt
sudo apt-get install libapache2-mod-php5 php5-cli php5-mysql php5-gd php5-mcrypt php5-json php-pear snmp fping mysql-server mysql-client python-mysqldb rrdtool subversion whois mtr-tiny ipmitool graphviz imagemagick libvirt ipmitool
### Creation MySQL Database and User for Observium ###
Now you need to log into MySQL and create database for **Observuim**:
mysql -u root -p
After successful authenticated, you need to create the database.
CREATE DATABASE observium;
The database Name is **Observium**. You will need this information later.
Now, you should create the database administrator.
CREATE USER observiumadmin@localhost IDENTIFIED BY 'observiumpassword';
Next, you need to give this user permissions to administer the database you created.
GRANT ALL PRIVILEGES ON observium.* TO observiumadmin@localhost;
You need to flush the privilege information to disk to activate the new MySQL user:
FLUSH PRIVILEGES;
exit
### Downloading and Installing Observium ###
Now that our system is ready, we can start the installation of Observium.
First step to do is, creating the directory Observium is going to operate out of:
mkdir -p /opt/observium && cd /opt
For the purpose of this tutorial, were going to be using the Community/Open Source Edition of Observium. Download and unpack it.
wget http://www.observium.org/observium-community-latest.tar.gz
tar zxvf observium-community-latest.tar.gz
Now go under Observium directory
cd observium
Copy the default configuration file **config.php.default** to **config.php** and fill out the database config options:
cp config.php.default config.php
nano config.php
----------
/ Database config
$config['db_host'] = 'localhost';
$config['db_user'] = 'observiumadmin';
$config['db_pass'] = 'observiumpassword';
$config['db_name'] = 'observium';
Lets setup the default schema for the MySQL Database:
php includes/update/update.php
Now you need to create directory to store rrd file and change permission to let apache write into the file .
mkdir rrd
chown apache:apache rrd
To help you troubleshooting on case of problem, you need to create logs file.
mkdir -p /var/log/observium
chown apache:apache /var/log/observium
Now you have to create the virtual host configuration for Observium
<VirtualHost *:80>
DocumentRoot /opt/observium/html/
ServerName observium.domain.com
CustomLog /var/log/observium/access_log combined
ErrorLog /var/log/observium/error_log
<Directory "/opt/observium/html/">
AllowOverride All
Options FollowSymLinks MultiViews
</Directory>
</VirtualHost>
Next, you need to enable rewrite functionality for your Apache server.
To enable `mod_rewrite` modules, type this command:
sudo a2enmod rewrite
This module will be enable the next after reboot of Apache service.
sudo service apache2 restart
### Configuring Observium ###
Before log into the web interface, you need to create administrator account (level 10) to Observium
# cd /opt/observium
# ./adduser.php admin adminpassword 10
User admin added successfully.
Next set a cron jobs for the discovery and the poller jobs, create a new file **/etc/cron.d/observium** and add the following contents.
33 */6 * * * root /opt/observium/discovery.php -h all >> /dev/null 2>&1
*/5 * * * * root /opt/observium/discovery.php -h new >> /dev/null 2>&1
*/5 * * * * root /opt/observium/poller-wrapper.py 1 >> /dev/null 2>&1
Reload cron process to take new entries.
# /etc/init.d/cron reload
Youve installed Observium Server! Log into Observium using your browser **http://<Server IP>** and be on your way.
![](https://www.unixmen.com/wp-content/uploads/2015/03/Capture.png)
Enjoy!
--------------------------------------------------------------------------------
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作者:[anismaj][a]
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How to Setup lftp - A Simple Command line FTP Program
================================================================================
Hi everyone, this article is about Lftp and how we can install Lftp in our Linux Operating System. [Lftp][1] is a command line based File Transfer Software also known as FTP Client which was developed by Alexander Lukyanov and was distributed as GNU General Public License. Besides FTP, it also supports FTPS, HTTP, HTTPS, HFTP, FISH, and SFTP. The program also supports FXP, allowing for data transfers between two FTP servers bypassing the client machine.
It has some awesome advanced features such as recursively mirroring entire directory trees and resuming downloads. Transfers can be scheduled for execution at a later time, bandwidth can be throttled, transfer queues can be created, and Unix shell-like job control is supported. The client can also be used interactively or automated with scripts.
### Installing Lftp ###
Before we try to run lftp, we have make sure that it is properly installed in our Linux Distribution. Here are some commands mentioned for installing lftp in the list common distribution of Linux.
**On Ubuntu 14.04 LTS**
In Ubuntu 14.04 LTS and its derivatives, we can install lftp using apt manager. So, to install it, we'll need to run the following commands in a shell or a terminal under sudo privilege.
$ sudo apt-get install lftp
![ubuntu install lftp](http://blog.linoxide.com/wp-content/uploads/2015/03/ubuntu-install-lftp.png)
**On CentOS/Fedora/RHEL**
As lftp is also available in the repository of Fedora, CentOS and RHEL, we can use **yum** manager to install it.
$ sudo yum install lftp
![fedora lftp](http://blog.linoxide.com/wp-content/uploads/2015/03/fedora-lftp.png)
**On Arch Linux**
It is also available in Arch Linux Package Repository so, we can simply use pacman to install it.
$ sudo pacman -S lftp
![archlinux install lftp](http://blog.linoxide.com/wp-content/uploads/2015/03/archlinux-install-lftp.png)
**On OpenSuse**
Zypper, package management software for OpenSuse can be used to install lftp. Here is the command with which one can install it on their OpenSuse machine.
$ sudo zypper install lftp
![opensuse lftp install](http://blog.linoxide.com/wp-content/uploads/2015/03/lftp_install.png)
### Logging in ###
To login to a ftp server or sftp server, we'll first need to know about the required credential for the login like username, password, ports.
After that, we'll want to login using lftp client as basic usage.
$ lftp ftp://linoxide@localhost
![ftp login](http://blog.linoxide.com/wp-content/uploads/2015/03/lftp-login.png)
If we need to point a port to the login then, we'll need to add port as shown below.
$ lftp ftp://linoxide@localhost:21
![ftp login with ports](http://blog.linoxide.com/wp-content/uploads/2015/03/lftp-login-port.png)
### Navigation ###
We can use **ls** to list files and directories, **cd** to enter into a directory.
![ls and cd](http://blog.linoxide.com/wp-content/uploads/2015/03/ls-cd-lftp.png)
### Uploading and Download Files ###
We can use **pget** for downloading files from the remote server.
> pget linspeed.svg
![pget lftp](http://blog.linoxide.com/wp-content/uploads/2015/03/pget-lftp.png)
We can use **put** for uploading files to the remote server.
> put linoxide.tar
![upload with put](http://blog.linoxide.com/wp-content/uploads/2015/03/put-upload.png)
To resume partially downloaded files/directories, we will use the -c switch:
> mirror -c Directory
>pget -c linoxide.tar
> put -c upload.tar
### Using Mirror ###
We can use mirror to download the whole directory pointed as the source.
> mirror remote local
![download with mirror](http://blog.linoxide.com/wp-content/uploads/2015/03/mirror.png)
There is also reverse mirror (mirror -R) which uploads or updates a directory tree on server.
> mirror -R local remote
![upload or update with mirror reverse](http://blog.linoxide.com/wp-content/uploads/2015/03/mirror-reverse.png)
To resume partially downloaded files/directories, we will use the -c switch:
> mirror -c Directory
### To Queue Items to Download ###
We can use queue option with lftp so that we can download selected files in a queue one by one as there is an option in GUI based clients to select and download in a queue. Here's an example on it.
To prevent queue from auto transferring while you add to it :
> queue stop
Now, we'll add them into queue.
> queue mirror "directory"
> queue pget "file.tar"
After the queue has been added, we should run queue start command.
> queue start
To remove the entire queue run the following command.
> queue -d
### Segmented Downloading ###
Here, in this example we are segmenting files into 3 segments, one can change it according to their own need.
A pget command using segmentation is **pget -n 3 file.tar**, where 3 is the number of segments.
> pget -n 3 file.tar
A mirror command using segmentation is **mirror --use-pget-n=3 directory**, where 3 is the number of segments.
> mirror --use-pget-n=3 linxoxide
We can use jobs -v to see the speeds of the individual segments as well as the total speed.
### To Stop, Resume or Kill a Transfer ###
To cancel a transfer we can press Ctrl+c . And to resume a download we can use the -c (--continue) switch as shown below.
> mirror -c directory
And to kill an active transfer we should run **kill** and to kill and delete all we'll need to run **kill all** as shown below.
> kill
> kill all
### Exiting ###
To quit from lftp, we should run exit command in the terminal or inside lftp interface.
> exit
### Conclusion ###
Hurray! We have successfully installed lftp and learned some basic major ways to use it. lftp is an awesome command line ftp client which supports a lot of additional functionality and cool features. It has a lot stuffs more than the other common ftp client. So, if you have any questions, suggestions, feedback please write them in the comment box below. Thank you ! Enjoy lftp :-)
--------------------------------------------------------------------------------
via: http://linoxide.com/linux-how-to/setup-lftp-command-line-ftp/
作者:[Arun Pyasi][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://linoxide.com/author/arunp/
[1]:http://lftp.yar.ru/

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translating by martin.
Nmap—Not Just for Evil!
================================================================================
If SSH is the Swiss Army knife of the system administration world, Nmap is a box of dynamite. It's really easy to misuse dynamite and blow your foot off, but it's also a very powerful tool that can do jobs that are impossible without it.
When most people think of Nmap, they think of scanning servers, looking for open ports to attack. Through the years, however, that same ability is incredibly useful when you're in charge of the server or computer in question. Whether you're trying to figure out what kind of server is using a specific IP address in your network or trying to lock down a new NAS device, scanning networks is incredibly useful.
Figure 1 shows a network scan of my QNAP NAS. The only thing I use the unit for is NFS and SMB file sharing, but as you can tell, it has a ton of ports wide open. Without Nmap, it would be difficult to figure out what the machine was running.
![](http://www.linuxjournal.com/files/linuxjournal.com/ufiles/imagecache/large-550px-centered/u1002061/11825nmapf1.jpg)
### Figure 1. Network Scan ###
Another incredibly useful way to use Nmap is to scan a network. You don't even have to have root access for that, and it's as simple as specifying the network block you want to scan. For example, typing:
nmap 192.168.1.0/24
will scan the entire range of 254 possible IP addresses on my local network and let me know which are pingable, along with which ports are open. If you've just plugged in a new piece of hardware, but don't know what IP address it grabbed via DHCP, Nmap is priceless. For example, the above command revealed this on my network:
Nmap scan report for TIVO-8480001903CCDDB.brainofshawn.com (192.168.1.220)
Host is up (0.0083s latency).
Not shown: 995 filtered ports
PORT STATE SERVICE
80/tcp open http
443/tcp open https
2190/tcp open tivoconnect
2191/tcp open tvbus
9080/tcp closed glrpc
This not only tells me the address of my new Tivo unit, but it also shows me what ports it has open. Thanks to its reliability, usability and borderline black hat abilities, Nmap gets this month's Editors' Choice award. It's not a new program, but if you're a Linux user, you should be using it!
--------------------------------------------------------------------------------
via: http://www.linuxjournal.com/content/nmap%E2%80%94not-just-evil
作者:[Shawn Powers][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://www.linuxjournal.com/users/shawn-powers

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CD音频抓取器——基于图形界面
================================================================================
CD音频抓取器是为了从光盘中提取“剖出”原始数字音频它在一个通常被称为CDDA的格式中并把它保存成文件或以其他形式输出而设计的。这类软件使用户能把数字音频编码成各种格式并能下载和上传在线CD目录服务——一个在线的光盘数据库——中的光盘信息。
复制CD合法吗在美国版权法中把一个原始CD转换成数字文件用于个人使用在被引用时等同于合理使用。然而美国版权法并没有明确的允许或禁止拷贝私人音频CD而且判例法还没有确立出在具体的哪种情况下可以视为合理使用。在英国版权的位置更清晰一些。从2014年开始英国公民制造CDMP3DVD蓝光和电子书的行为成为合法行为。这仅适用于这个人拥有被采集的媒体的实体并且复制品仅用于他们个人使用。对于欧盟的其他国家成员国可以允许私人复制这种特例。
如果你不确定在你生活的国家里版权处于什么位置,在你使用这两页文章中所列举的软件前请查询本地的版权法以确定你处在合法的一边。
在某种程度上提取CD音轨看起来有点多余。如Spotify和Google Play Music这类流服务提供了一个巨大的以通用格式存在的音乐的库无需采集你的CD集。但是如果你已将收藏了一个数量巨大的CD集。能把你的CD转换成可以在便携设备如智能手机、平板和便携式MP3播放器上播放的格式仍然是个诱人的选择。
这两页文章推荐了我最喜欢的音频CD抓取器。我挑了四个最好的图形界面的音频抓取器四个最好的控制台音频抓取器。所有这些应用程序都是在开源许可下发行的。
----------
![](http://www.linuxlinks.com/portal/content2/png/freac.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-freac.png)
fre:ac是个开源音频转换器和CD提取器支持很多种流行格式和编码器。目前这个应用可以在MA3、MP4/M4A、WMA、Ogg Vorbis、FLAC、AAC、WAV和Bonk格式间转换。这来源于几种不同形式的LAME编码器。
#### 功能包括: ####
- 易学易用
- MP3、MP4/M4A、WMA、Ogg Vorbis、FLAC、AAC、WAV和Bonk格式转换器
- 集成了CDDB/freedb标题数据库支持的CD提取器
- 多核优化的编码器加速了现代PC上的转换速度
- 对于标签和文件名称的全Unicode支持
- 易学易用,当你需要时还提供专家级选项
- 任务列表
- 可以使用Winamp 2加入附件
- 多语言用户界面可以使用41种语言
- 网址: [freac.org][1]
- 开发人员Robert Kausch
- 许可证: GNU GPL v2
- 版本号: 20141005
----------
![](http://www.linuxlinks.com/portal/content2/png/Audex.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-Audex.png)
Audex是个简单易用的开源音频CD提取应用。虽然它还处于早期开发阶段这个KDE桌面工具足够稳定、聪明和简单可以使用。
助手可以给LAME、OGG Vorbisoggenc、FLAC、FAACAAC/MP4和RIFF WAVE创建配置文件。除去这个助手你可以定义你自己的配置文件这意味着Audex适用于大部分的命令行编码器。
#### 功能包括: ####
- 可提取CDDA Paranoia
- 提取和编码同时进行
- 文件名采用本地和远程CDDB/FreeDB数据库
- 提供新的CDDB/FreeDB数据库入口
- 类似capitalize的元数据纠正工具
- 多配置文件提取(每个配置文件文件有一个命令行编码器)
- 从互联网上抓取封面并将他们存在数据库中
- 在目标目录中创建播放列表、封面和基于模板的信息文件
- 创建提取和编码协议
- 将文件传送到FTP服务器
- 支持国际化
- 网址: [kde.maniatek.com/audex][2]
- 开发人员: Marco Nelles
- 许可证: GNU GPL v3
- 版本号: 0.79
----------
![](http://www.linuxlinks.com/portal/content2/png/SoundJuicer.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-SoundJuicer.png)
Sound Juicer是个使用GTK+和GStreamer的轻量级CD提取器。它从CD中提取音频并把它转换成音频文件。Sound Juicer还可以直接播放CD中的音轨在提取前提供预览。
由于GStreamer插件它支持任何音频编码包括 MP3、Ogg Vorbis、FLAC和未压缩的PCM格式。
它是GNOME桌面环境已建成的一部分。
#### 功能包括: ####
- 自动通过CDDB给音轨加标签
- 可编码成ogg/vorbis、FLAC和原始WAV
- 编码路径的设置很简单
- 多种流派
- 国际化支持
- 网址:[burtonini.com][3]
- 开发人员: Ross Burton
- 许可证GNU GPL v2
- 版本号3.14
----------
![](http://www.linuxlinks.com/portal/content2/png/ripperX.png)
![](http://www.linuxlinks.com/portal/content/reviews/Utilities/Screenshot-ripperX.png)
ripperX是个开源的图形交互界面用于提取CD音轨并把他们编码成Ogg、MP2、MP3或FLAC格式。它的目的是容易使用只需要点几下鼠标就能转换整张专辑。它支持在CDDB寻找专辑和音轨信息。
他使用cdparanoia把CD音轨转换也就是“提取”成WAV文件然后访问Vorbis/Ogg编码器oggenc把WAV文件转换成OGG文件。它还可以访问flac让WAV文件有无损压缩的表现制成FLAC文件。
#### 功能包括: ####
- 非常简单易用
- 可以把CD音轨提取成WAV、MP3、OGG或FLAC文件
- 支持CDDB查找
- 支持ID3v2标签
- 可暂停提取进程
- 网址:[sourceforge.net/projects/ripperx][4]
- 开发人员Marc André Tanner
- 许可证MIT/X Consortium License
- 版本号2.8.0
--------------------------------------------------------------------------------
转自http://www.linuxlinks.com/article/20150125043738417/AudioGrabbersGraphical.html
作者Frazer Kline
译者:[H-mudcup](https://github.com/H-mudcup)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[1]:http://www.freac.org/
[2]:http://kde.maniatek.com/audex/
[3]:http://burtonini.com/blog/computers/sound-juicer
[4]:http://sourceforge.net/projects/ripperx/

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Ubuntu 15.04 最终实现你可以设置你的菜单 ‘始终可见’
================================================================================
**如果你不喜欢 Unity 的全局菜单在你的鼠标离开后就淡出你的视野, Ubuntu 15.04 有一些额外附加去实现这点.**
![](http://www.omgubuntu.co.uk/wp-content/uploads/2014/02/locally-integrated-menus-in-ubuntu.png)
最新的Ubuntu 15.04的Unity界面通过在提议通道提供了一个选项**使应用程序菜单在Ubuntu中可见**.
不时尚, 不过时, 没有丢失的菜单.
最大的缺点是它目前只能通过dconf来控制而不是常规的面向用户的选项设置。
我希望如果不是期望能有一个设置这个特性的选项被加入到Ubuntu的【系统设置】>【外观】部分的开发仍在继续。
现在如果你使用的是Ubuntu15.04并启用“建议”的更新通道后你会发现这个开关存在于在COM>规范>Unity>“始终显示菜单”。
### 迟到总比没有要好? ###
开发者计划在Ubuntu14.04 LTS的下一个SRU中反向移植这个选项假设在测试阶段没有任何意外发生
本地集成菜单LIM在Ubuntu 14.04 LTS 首次获得了欣赏,被广泛认为在那些喜欢隐藏方式的和那些不喜欢必须使用鼠标和触摸板的人之间的最佳的折衷方法
虽然本地集成菜单给我们带来了半路上沉默的批评在统一方面,默认的“淡入/淡出”行为给我们留下了令人发痒的伤痕
在Ubuntu 过去的几个版本中已经能够看到积极的去解决早期UX的经历过的关切的问题。在经过几年“打算去做”的列表[我们去年终于得到了本地集成菜单][1],以及不支持的通过点击图标实现[减少和恢复Unity启动程序中不支持的应用程序的选项]。
一年以来我们终于得到一个选项以使应用程序菜单始终显示,无论我们的鼠标在哪里。迟来总比没有好,对不对?
--------------------------------------------------------------------------------
via: http://www.omgubuntu.co.uk/2015/01/ubuntu-15-04-always-show-menu-bar-option
作者:[Joey-Elijah Sneddon][a]
译者:[JeffDing](https://github.com/JeffDing)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:https://plus.google.com/117485690627814051450/?rel=author
[1]:http://www.omgubuntu.co.uk/2014/02/locally-integrated-menus-ubuntu-14-04
[2]:http://www.omgubuntu.co.uk/2014/03/minimize-click-launcher-option-ubuntu-14-04

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既然float不能表示所有的int那为什么在类型转换时C++将int转换成float
---------
#问题
代码如下:
```C
int i = 23;
float f = 3.14;
if (i == f) // 执行某段代码
```
编译器会将i转换成float类型然后比较这两个float的大小但是float能够表示所有的int吗为什么没有将int和float转换成double类型进行比较呢
#回答
在整型数的演变中,当`int`变成`unsigned`时,会丢掉负数部分(有趣的是,这样的话,`0u < -1`就是对的了
和C语言中的大部分机制在C++中得到继承一样就硬件操作而言常见的算术转换应该简明易懂。C语言的发明者精通他们所使用机器上的汇编语言他们编写的C语言对他们和像他们一样编写程序的人有直接的意义直到使用汇编语言编写诸如UNIX内核的程序时。
现如今一般来说处理器并不具有混合类型的指令系统如float和double相加、比较int和float诸如此类因为如果这样做造成芯片晶圆的巨大浪费——如果你想支持更多不同的类型你不得不实现更多的操作码。然而在实际中你只有实现"add int to int"、"compare float to float"和"multiply unsigned with unsigned"等功能的常见指令,这使得优先进行算术转换变得很有必要——它们是指令系统中两种类型的映射关系,它们中的大部分很有用处。
从习惯编写低级别机器代码的编程人员的角度来说如果有了混合类型那么在一般情况下最有可能使用的汇编指令就是那些只需要进行最少类型转换的指令。其中有一种特殊情况就是浮点数的转换特别是在20世纪70年代早期当时C语言正在被开发计算机运行速度很慢而浮点数的计算是通过软件完成的所以进行转换的成本很高。这拖慢了常用算术运算的转换开发——当时只有一种操作数实现了转换这个例外就是long到unsigned int的转换这种转换没有任何要求在大部分机器上都可以进行。当然并不是全部因为总有例外情况
所以,编写常用的算术转换是为了完成汇编程序员在大部分时间需要做的事情:即有两种不匹配的类型,将一种转换成另一种。这也就是汇编代码所做的事情,除非有特别原因需要进行其它类型转换。对于那些习惯编写汇编代码的人来说,除非是特殊需要,才会被迫去编写一种不同的类型转换。显然,这种情况下提出编写转换是很自然的事情。虽然,你可以简单地写成这样
```C
if((double) i < (double) f)
```
顺便提一下,在这个问题中有趣的是,`unsigned`的优先级高于`int`,所以把`int`和`unsigned`进行比较时最终进行的是unsigned类型的比较开头提到的`0u < -1`就是这个道理我猜测这可能是在早些时候计算机发展初期当时的人们认为`unsigned``int`在所表示的数值范围上受到的限制更小现在还不需要符号位所以可以使用额外的位来表示更大的数值范围如果你觉得`int`可能会溢出那么就使用unsigned好了在使用16位表示的ints时这个担心会更明显
----
via:[stackoverflow](http://stackoverflow.com/questions/28010565/why-does-c-promote-an-int-to-a-float-when-a-float-cannot-represent-all-int-val/28011249#28011249)
作者:[wintermute][a]
译者:[KayGuoWhu](https://github.com/KayGuoWhu)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://stackoverflow.com/users/4301306/wintermute

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9款最好的Javacript用户的IDE和代码编辑器。
================================================================================
网络应用设计和开发是最近一段时间的发展趋势也有越来越多的人开始在此寻找他们的职业机会。但是作为网络开发人员或图形设计人员来说一个好的机会并不是每个人都能够轻易获得到的它需要很好的思维展现以及对于工作的熟练技巧。现在有许多可用的网站来根据你的知识帮助你找到正确的工作描述。但是如果你想要在这个领域有所成就你仍然需要具有一些出色的手段例如可以在不同的平台、IDE以及其他的工具上开展工作。
说到根据不同目的所使用的大量语言用到的不同平台以及IDE只靠学习一个IDE来容易地获取项目设计的最佳方案的惯例已经属于过去时了。今天我们活在一个竞争日益激烈的现代生活节奏中对于IDE们也是相同的处境IDE是一个用来创建和部署应用的强大的客户端应用。今天我们打算为网络设计者和开发人员分享一些最好的Javacript IDE。
请访问作为javascript 用户最好的代码编辑器列表,并将你的想法与我们一起分享。
### 1) [Spket][1] ###
**Spket IDE** 是JavaScript和XML开发的强大工具包。该编辑器可以用来进行开发 JavaScriptXUL/XBL 和Yahoo小组件。 JavaScript编辑器提供了例如代码补全语法高亮以及代码内容大纲等特性可以帮助开发者提高创建高效JavaScript代码的生产率。
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/spket-e1422674329554.png)
### 2) [Ixedit][2] ###
IxEdit 基于Javascript交互的网络设计工具。通过IxEdit,设计者可以在不需要通过代码改变添加删除或变换页面元素的情况下在网页上进行动态进行DOM脚本编写。
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/ixedit.png)
### 3) [Komodo Edit][3] ###
Komodo是一款免费而强大的编辑器可以用来编辑JavaScript和其他的编程语言。
![](http://i2.wp.com/devzum.com/wp-content/uploads/2015/01/komodo-edit-e1422674596277.png)
### 4) [EpicEditor][4] ###
EpicEditor是一个可嵌入的 JavaScript Markdown编辑器具有分割全屏进行编辑实时预览自动草稿保存离线支持等特性。对于开发人员它提供了健壮的API可以容易地设置主题并允许你以任何其他的事物来替换绑定的Markdown解析器。
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/epiceditor-e1422674732281.png)
### 5) [codepress][5] ###
CodePress是一个用JavaScript编写的基于网络的源代码编辑器具有语法高亮,并且是在你将代码输入到浏览器后实时进行文本颜色渲染。
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/codepres-e1422674893706.png)
### 6) [ACe][6] ###
Ace 是一个使用JavaScript编写的嵌入式代码编辑器它能够匹配宿主编辑器的特性和性能例如SublimeVim和Textate。它能够容易地嵌入到任何的网页和JavaScript应用中。
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/ace-e1422675089912.png)
### 7) [scripted][7] ###
Scripted是一个快速的轻量级代码编辑器最初是为了JavaScript编写实现的。 Scripted是一个基于浏览器的编辑器而编辑器本身有本地运行的Node.js服务器实例来提供服务支持。
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/scripted-e1422675188408.png)
### 8) [Netbeans][8] ###
这是另外的一个更加震撼而且有用的编辑器可以用来编写javascript和其他的编程语言。
![](http://i1.wp.com/devzum.com/wp-content/uploads/2015/01/code_editing1-e1422675506226.png)
### 9) [Webstorm][9] ###
这是最智能的JavaScript IDE。 它是为使用Node.js进行复杂的客户端开发和服务器端开发而装备的一个轻巧而强大的完美IDE。
![](http://i0.wp.com/devzum.com/wp-content/uploads/2015/01/webstorm.png)
--------------------------------------------------------------------------------
via: http://devzum.com/2015/01/31/9-best-ides-and-code-editors-for-javascript-users/
作者:[vikas][a]
译者:[theo-l](https://github.com/theo-l)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://devzum.com/author/vikas/
[1]:http://spket.com/
[2]:http://www.ixedit.com/
[3]:http://komodoide.com/komodo-edit/
[4]:http://oscargodson.github.io/EpicEditor/
[5]:http://codepress.sourceforge.net/
[6]:http://ace.c9.io/#nav=about
[7]:https://github.com/scripted-editor/scripted
[8]:https://netbeans.org/
[9]:http://www.jetbrains.com/webstorm/

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@ -0,0 +1,196 @@
在linux中如何通过nload来监控网络使用情况
================================================================================
nload 是一个免费的linux工具,通过提供两个简单的图形化界面来帮助linux用户和系统管理员来实时监控网络流量以及宽带使用情况:一个作为进入流量,一个作为流出流量.
我是真的很喜欢用**nload**来在屏幕上显示当前的下载速度总的流入量和平均下载速度等信息。nload工具的报告图非常容易理解最重要的是这些信息真的非常有用。
在使用手册上说到,在默认情况下会监控所有网络设备。但是你可以轻松地指定你想要监控的设备,而且可以可以通过方向键头在不同的网络设备之间进行转换。另外还有很多的选项可用,例如 -r选项确定以毫秒来刷新显示时间间隔默认时间间隔值是500毫秒-m选项用来实时显示多个设备流量图在使用该选项时不会显示 -u选项用来设置显示流量数字的单元类型另外还有许多其他的选项将会在该教程中探索和练习。
### 如何将 nload安装到你的linux机器上 ###
**Ubuntu** 和 **Fedora** 用户可以从默认的软件仓库中容易地安装。
在Ubuntu上使用以下命令进行安装。
sudo apt-get install nload
在Fedora上使用以下命令进行安装。
sudo yum install nload
**CentOS**用户该怎么办呢? 只需要在你的机器上输入以下命令,通用能够达到相同的结果--殊途同归。
sudo yum install nload
以下的命令会帮助你在OpenBSD系统中安装nload.
sudo pkg_add -i nload
linux机器上的另外一个非常有效的安装软件的方式就是编译源代码通过下载并安装最新的版本意味着能够获得更好地性能更酷的特性以及越少的bug数。
### 如何通过源代码安装nload ###
在从源代码安装nload之前你需要首先下载源代码。 我通常使用wget工具来进行下载--该工具在许多linux机器上默认可用。该免费工具帮助用户以非交互式的方式从网络上下载文件并支持以下协议
- HTTP
- HTTPS
- FTP
通过以下命令来进入到**/tmp**目录中。
cd /tmp
然后在你的终端中输入以下命令就可以将最新版本的nload下载到你的linux机器上了。
wget http://www.roland-riegel.de/nload/nload-0.7.4.tar.gz
如果你不喜欢使用wget工具也可以通过简单的一个鼠标点击轻松地从[官网][1]上下载源代码。
由于该软件非常轻巧,其下载过程几乎在瞬间就会完成。接下来的步骤就是通过**tar**工具来将下载的源代码包进行解压。
tar归档工具可以用来从磁带或硬盘文档中存储或解压文件该工具具有许多可用的选项但是我们只需要下面的几个选项来执行我们的操作。
1. **-x** to extract files from an archive
1. **-x** 从文档中解压文件
1. **-v** to run in verbose mode
1. **-v** 使用繁琐模式运行--用来输入详细信息
1. **-f** to specify the files
1. **-f** 用来指定文件
例如:
tar xvf example.tar
现在你学会了如何使用tar工具我可以非常肯定你会知道如何从命令行中解压.tar文档。
tar xvf nload-0.7.4.tar.gz
之后使用cd命令来进入到nload*目录中
cd nload*
在我的系统上看起来是这样的
oltjano@baby:/tmp/nload-0.7.4$
然后运行下面这个命令来为你的系统配置包
./configure
此时会有一大波僵尸会在你的屏幕上显示出来,下面的一个屏幕截图描述了它的样子。
![configuring packages for nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload1.png)
在上述命令完成之后通过下面的命令来编译nload。
make
![compiling nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload2.png)
好了,终于....下载通过以下命令可以将nload安装在你的机器上了。
sudo make install
![installing nload from source](http://blog.linoxide.com/wp-content/uploads/2015/01/nload3.png)
安装好nload之后就是时间来让你学习如何使用它了。
###如何使用nload###
我喜欢探索,所以在你的终端输入以下命令.
nload
看到了什么?
我得到了下面的结果。
![running nload](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.png)
如上述截图可以看到,我得到了以下信息:
### 流入量###
#### 当前下载速度####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.1.png)
#### 平均下载速度####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.2.png)
#### 最小下载速度####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.3.png)
#### 最大下载速度####
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.4.png)
#### 总的流入量按字节进行显示####
![](http://blog.linoxide.com/wp-content/uploads/2015/01/nload4.5.png)
### 流出量 ###
类似的同样适用于流出量
#### 一些nload有用的选项####
使用选项
-u
用来设置显示流量单元的类型.
下面的命令会帮助你使用MBit/s显示单元
nload -u m
下面的屏幕截图显示了上述命令的结果.
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload5.png)
尝试以下命令然后看看有什么结果.
nload -u g
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload6.png)
同时还有一个**-U**选项.根据手册描述,该选项基本上与-u选项类似,只是用在合计数据. 我测试了这个命令,老实说,当你需要检查总的流入与流出量时非常有用.
nload -U G
![nload running on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload7.png)
从上面的截图中可以看到,**nload -U G** 使用Gbyte来显示数据总量.
另外一个我喜欢使用的有用选项是 **-t**. 该选项用来设置刷新显示事件间隔为毫秒,默认值为500毫秒.
我会通过下面的命令做一些小的实验.
nload -t 130
那么上述命令做了什么呢,它讲刷新显示时间间隔设置为130毫秒. 通常推荐不要讲该时间间隔值设置为小于100毫秒,因为nload在计算过程中可能会生成带错的报告.
另外的一个选项为 **-a**. 在你想要设置计算平均值的时间窗口秒数长度时使用,默认该值为300秒.
那么当你想要监控指定的网络设备该如何呢? 非常容易, 想下面这样简单地指定设备或者列出想要监控的设备列表.
nload wlan0
![nload monitoring wlan0 on linux](http://blog.linoxide.com/wp-content/uploads/2015/01/nload8.png)
下面的语法可帮助你监控指定的多个设备.
nload [options] device1 device2 devicen
例如,使用下面的命令来监控eth0和eth1.
nload wlan0 eth0
如果不带选项来运行nload,那么它会监控监控所有自动检测到的设备,你可以通过左右方向键来显示其中的任何一个设备的信息.
--------------------------------------------------------------------------------
via: http://linoxide.com/monitoring-2/monitor-network-usage-nload/
作者:[Oltjano Terpollari][a]
译者:[theo-l](https://github.com/theo-l)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://linoxide.com/author/oltjano/
[1]:http://www.roland-riegel.de/nload/nload-0.7.4.tar.gz

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@ -0,0 +1,55 @@
Linux 常见问题解答--如何使用yum来下载RPM包而不进行安装.
================================================================================
> **问题**:我想从Red Hat's的标准仓库中下载一个RPM包,我能使用yum命令来下载一个RPM包但是不进行安装吗?
yum是基于Red Hat的系统(如CentOS,Fedora,RHEl)上的默认包管理器.使用yum,你可以安装或者更新一个RPM包,并且他会自动解决包依赖关系.但是如果你只想将一个RPM包下载到你的系统上该怎么办呢? 例如,你可能想要获取一些RPM包在以后使用,或者将他们安装在另外的机器上.
这里说明了如何从yum仓库上下载一个RPM包.
### 方法一:yum###
yum命令本身就可以用来下载一个RPM包,标准的yum命令提供了`--downloadonly(只下载)`的选项来达到这个目的.
$ sudo yum install --downloadonly <package-name>
默认情况下,一个下载的RPM包会保存在下面的目录中:
/var/cache/yum/x86_64/[centos/fedora-version]/[repository]/packages
以上的[repository]表示下载包的来源仓库的名称(例如,base,fedora,updates)
如果你想要讲一个包下载到一个指定的目录(如/tmp):
$ sudo yum install --downloadonly --downloaddir=/tmp <package-name>
注意,如果下载的包包含了任意没有满足的依赖关系,yum将会把所有的依赖关系包下载,但是都不会被安装.
另外一个重要的事情时,在CentOS/RHEL 6或更早期的版本中,你需要安装一个单独yum插件(名称为 yum-plugin-downloadonly)才能使用`--downloadonly`命令选项:
$ sudo yum install yum-plugin-downloadonly
如果没有该插件,你会在使用yum时得到以下错误:
Command line error: no such option: --downloadonly
![](https://farm9.staticflickr.com/8627/15571201803_38390aae75_c.jpg)
### 方法二: Yumdownloader###
另外一个下载RPM包的方法就是通过一个专门的包下载工具--yumdownloader. 这个工具时yum工具包(包含了用来进行yum包管理的帮助工具套件)的子集.
$ sudo yum install yum-utils
下载一个RPM包:
$ sudo yumdownloader <package-name>
下载的包会被保存在当前目录中.你需要使用root权限,因为yumdownloader会在下载过程中更新包索引文件.与yum命令不同的是,任何依赖包不会被下载.
--------------------------------------------------------------------------------
via: http://ask.xmodulo.com/yum-download-rpm-package.html
译者:[theo-l](https://github.com/theo-l)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出

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@ -6,7 +6,7 @@ Linux有问必答如何在Debian或Ubuntu上安装完整的内核源码
只有在你需要生成一个定制的内核,而且内核源码中的一些内核默认设置要被你调整了的情况下,你才需要完整的内核源码树。
这里将会解答如何**在Debian或Ubuntu的库中下载并安装完整树结构的内核源码**。虽然你可以在这个网站[https://www.kernel.org/pub/linux/kernel/][2]下载官方的内核源码,但是发行版软件仓库可以允许你下载包含补丁的内核源码。
这里将会解答如何**在Debian或Ubuntu的库中下载并安装完整树结构的内核源码**。你可以在[https://www.kernel.org/pub/linux/kernel/][2]下载官方的内核源码,不过使用发行版软件仓库可以允许你下载包含补丁的内核源码。
### 在Debian上安装完整的内核源码 ###
@ -20,7 +20,7 @@ Linux有问必答如何在Debian或Ubuntu上安装完整的内核源码
伴随着完整内核源码linux_X.X.XX.orig.tar.xz的还有一些可用的内核补丁linux_X.X.X+XXX.debian.tar.xz和源码控制文件linux_XXXX.dsc这些都将被下载并存储到当前目录。在.dsc文件中会指出如何给内核源码打补丁。
当下载完成以上的命令将会自动调用工具dpkg-source将下载的内核源码解压到当前的目录中与此同时更具.dsc文件来下补丁。
当下载完成以上的命令将会自动调用工具dpkg-source将下载的内核源码解压到当前的目录中与此同时根据.dsc文件来下补丁。
最终完整的内核源码树将会以"linux-X.X.XX"的形式呈现在当前目录中。
@ -35,7 +35,7 @@ Linux有问必答如何在Debian或Ubuntu上安装完整的内核源码
$ sudo apt-get install git
$ git clone git://kernel.ubuntu.com/ubuntu/ubuntu-$(lsb_release --codename | cut -f2).git
举个例子如果你使用的是Ubuntu14.04以上的命令将会查看Git的"ubuntu-trusty"仓库中的代码。
举个例子如果你使用的是Ubuntu 14.04以上的命令将会查看Git的"ubuntu-trusty"仓库中的代码。
![](https://farm9.staticflickr.com/8642/16526856391_de636ff9b8_c.jpg)
@ -49,7 +49,7 @@ via: http://ask.xmodulo.com/install-full-kernel-source-debian-ubuntu.html
作者:[Dan Nanni][a]
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
校对:[Caroline](https://github.com/carolinewuyan)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出

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@ -1,8 +1,8 @@
How To Fix: Failed to fetch cdrom apt-get update cannot be used to add new CD-ROMs
如何修复apt-get update无法添加新的CD-ROM
================================================================================
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2014/12/elementary_OS_Freya.jpg)
These days I am experimenting with Elementary OS Freya and during this, I encountered a very common updater error: **Failed to fetch cdrom Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs**. The complete error looked like this after running the apt-get update command:
这些天我正在体验Elementary OS Freya在这期间我遇到了一个非常常见的更新错误**Failed to fetch cdrom Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs**。完整的错误在运行apt-get update后看上去像这样
> W: Failed to fetch cdrom://elementary OS 0.3 _Freya_ Daily amd64 (20150208)/dists/trusty/main/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
>
@ -10,33 +10,33 @@ These days I am experimenting with Elementary OS Freya and during this, I encoun
>
> E: Some index files failed to download. They have been ignored, or old ones used instead.
In this post, we shall see how to fix this error.
本篇中,我们会了解如何修复这个错误。
### Fix Failed to fetch cdrom apt-get update cannot be used to add new CD-ROMs error ###
### 修复apt-get update无法添加新的CD-ROM的错误 ###
The reason for this error is that cdrom has been included as one of the the sources here. And to fix this issue, we need to remove this from the list of software sources.
这个错误的原因是cdrom已经被包含在源之中。要修复这个问题我们需要将它从软件源中移除。
In Ubuntu, look for Software & Updates:
在Ubuntu中找到“软件与更新”
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2014/08/Software_Update_Ubuntu.jpeg)
In the first tab Ubuntu Software, look for the cdrom, if its checked, uncheck it.
在Ubuntu Software的第一个标签中找到cdrom如果它是勾选的那么取消勾选。
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/02/CDROM_Error_Update_Software_Sources.jpeg)
Close the Software Sources and run the update again. It should work fine now.
关闭软件源并再次运行更新。现在应该可以用了。
### Further troubleshoot: ###
### 进一步故障排除: ###
The method described above should have fixed this **apt-get update cannot be used to add new CD-ROMs** error. But this was not the case for me because the option of cdrom was already grayed out as I was using live session.
上面描述的方法已经修复了这个**apt-get update cannot be used to add new CD-ROMs**错误。但是这个方法对我无效因为cdrom的选项这时是灰色的因为我使用的live版本。
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/02/CDROM_Update_Error.png)
Now to fix our error, we shall take the command line route. Open a terminal and use the following line to see what is included in sources list:
现在要修复我们的问题了,我们是要采用命令行路线。打开终端并查看软件源中包含了哪些源:
cat /etc/apt/sources.list
The output for me was as following:
我的输出是下面这样:
deb cdrom:[elementary OS 0.3 _Freya_ Daily amd64 (20150208)]/ trusty main restricted
deb http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
@ -46,17 +46,17 @@ The output for me was as following:
deb http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
Look at the first line in the above list. It includes cdrom. We need to comment out this line by adding # in front of it to make it look like this:
在上面的第一行中。它包含了cdrom。我们需要用#’来注释掉这行:
#deb cdrom:[elementary OS 0.3 _Freya_ Daily amd64 (20150208)]/ trusty main restricted
To do that use the command below:
要用下面的命令来:
sudo gedit /etc/apt/sources.list
Once you have edited the sources.list, run the apt-get update once again. The error apt-get update cannot be used to add new CD-ROMs should have been fixed. If you are facing any other update issue, do look at this article which is a collection of most [common Ubuntu update error fixes][1].
在你编辑完软件源后再次运行apt-get update。“apt-get update cannot be used to add new CD-ROMs”这个错误应该已经修复了。如果你还遇到其他的问题看一下这篇收集了大部分[Ubuntu常见更新错误修复][1]的文章。
I hope you found this tutorial helpful. If you have any questions or suggestions, feel free to drop a comment.
我希望这篇教程对你有用。如果你还有其他的问题和建议,请在下面留言。
--------------------------------------------------------------------------------
@ -69,4 +69,4 @@ via: http://itsfoss.com/fix-failed-fetch-cdrom-aptget-update-add-cdroms/
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://itsfoss.com/author/abhishek/
[1]:http://itsfoss.com/fix-update-errors-ubuntu-1404/
[1]:http://itsfoss.com/fix-update-errors-ubuntu-1404/

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@ -0,0 +1,85 @@
设置Ubuntu14.04无密码登录SSH
================================================================================
大家好今天我来向大家介绍如何在可信的Ubuntu12.04上设置无密码登录SSH功能。仅在工作站有正确的公私密钥以供匹配时SSH服务端才会允许你登录反之访问将不会被允许。
正常情况下我们需要连上SSH的控制台输入用户名和密码两者结合使用。如果两者全部正确我们就可以访问反之访问被服务端拒绝。不过相比而言还有一种比用密码更安全的登录方式我们用的不是密码在登录SSH我们用的是密钥。
如果你想使用这个安全的方式我们只需简单的禁用密码登录并只允许密钥即可。使用这种方式时客户端计算机上会产生公私一对密钥。接着客户端得把公钥上传到SSH服务端的密要验证文件中去。在访问被授予前服务器及客户端电脑互验密钥对。如果服务器上的公钥与客服端提交的私钥匹配访问开始否则访问被拒绝。
这是获取SSH服务器认证中非常安全的一种做法如果你想为SSH用户登录实施安全的认证这也是备受推崇的方式。这里快速的过一遍允许无密码登录SSH的配置过程。
### 1.安装Openssh服务端 ###
首先我们需要更新我们的本地库索引。所以如下所见我们需要先输入“apt-get update”
$ sudo apt-get update
![Updating Repo Index](http://blog.linoxide.com/wp-content/uploads/2015/02/updating-repo-list.png)
现在我们可以通过以下命令安装openssh-server
$ sudo apt-get install openssh-server
![Installing openssh server](http://blog.linoxide.com/wp-content/uploads/2015/02/installing-openssh-server.png)
### 2. 开启openssh服务 ###
在OpenSSH已经成功安装在Ubuntu14.04操作系统上了之后我们要启动OpenSSH的服务。以下命令让你启动/开启服务。
$ sudo service ssh start
OR
$ sudo /etc/init.d/ssh start
### 3. 配置密钥对 ###
在我们安装并启动了OpenSSH服务以后。现在终于到了要我们搞定公私钥对的时候了在终端中运行以下命令
$ ssh-keygen -t rsa
在运行完以上命令了以后,我们完成一系列的提示的任务。首先选择保存密钥路径,按回车将会选择默认路径即家目录的一个隐藏的.ssh文件夹。下一个提示是请输入提醒。我个人将此留白回车过。之后密钥对就会创建大功告成。
![Generating Key Pair](http://blog.linoxide.com/wp-content/uploads/2015/02/generating-key-pair.png)
在密钥对生成以后,我们需要将**客户端的上的公钥复制到SSH服务端**或者宿主来创建对客户端的信任关系。运行以下命令复制客户端的公钥到服务端。
$ ssh-copy-id user@ip_address
在公钥上传之后我们现在可以不用通过密码登陆SSH了。为此我们需要通过以下命令用文本编辑器打开**etc/ssh/ssh_config**。
$ sudo nano /etc/ssh/sshd_config
现在,我们需要按照下图所示去到几行注释并进行一些赋值。
![Configuring sshd Config](http://blog.linoxide.com/wp-content/uploads/2015/02/configuring-sshd_config.png)
### 4. 重启SSH服务 ###
最后在我们配置完SSH服务端后为了使改动生效我们需要重启SSH服务。在终端或控制台运行以下命令重启。
$ sudo service ssh restart
OR
$ sudo /etc/init.d/ssh restart
![Restarting ssh](http://blog.linoxide.com/wp-content/uploads/2015/02/restarting-ssh.png)
现在我们可以试试不用密码仅用密钥配对的方式登录ssh服务端了。
### 总结 ###
太好了我们成功的配置了无密码登录SSH。这是获取SSH服务器认证中非常安全的一种做法如果你想为SSH但用户登录实施安全的认证这也是备受推崇的方式。所以如果你还有什么问题或建议请在意见框中向我们反馈。很欣慰你能读完祝你SSH登录愉快 :-)
--------------------------------------------------------------------------------
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如何在Ubuntu上修复“Not Enough Free Disk Space On /boot”
================================================================================
### 提问:如何在Ubuntu上修复“Not Enough Free Disk Space On /boot”错误###
今天当我在升级Lubuntu 14.04的时候遇到了下面这个错误,但是很简单。
> “Not Enough Free Disk Space On /boot”
![](https://www.unixmen.com/wp-content/uploads/2015/02/Software-Updater_002.png)
这是因为我的启动分区超出了不再要的旧内核与包等。
### 回答: ###
我听说**Computer Janitor**这个特性可以在Ubuntu Tweak中删除不想要的垃圾文件。使用Computer Janitor你可以将你的系统清理成像新安装的那样。Janitor会删除:
- 程序缓存(Firefox/Chrome 缓存、软件中心缓存);
- 略缩图缓存;
- apt缓存;
- 旧内核;
- 包的配置;
- 不再需要的包。
If you havent install this tool, look at the following link.
如果你还没有安装这个工具,参考下面的链接
- **[如何安装和使用Ubuntu Tweak][1]**
要删除不需要的垃圾文件打开Ubuntu Tweak点击 **Janitor** 选项。
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_006.png)
选择你想要删除的文件的选框,并点击 **Clean** 按钮。
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_007.png)
Janitor现在就开始清理你的系统了。
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_003.png)
真酷!系统清理完成了。
![](https://www.unixmen.com/wp-content/uploads/2015/02/Ubuntu-Tweak_008.png)
我重启启动了软件更新。这个没再遇到问题了。
![](https://www.unixmen.com/wp-content/uploads/2015/02/Software-Updater_009.png)
就是这样。当然也有其他的方法可以清理系统。但是,这个方法很容易学。我们可以只点击几次鼠标就可以清理系统。
干杯!
--------------------------------------------------------------------------------
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如何修复Windows更新在0%卡住
================================================================================
当你在一个月后登录Windows发现有一些更新需要安装 你选择安装这些更新但是**Windows更新卡在0%**时你感觉怎么样?
为什么我在Linux和开源专属的博客上谈论Windows更新呢因为我喜欢[双启动Windows和Linux][1]。当我使用Linux作为我的主桌面时过了一段时间我登录到Windows中。登录Windows后最烦人的事情是Windows更新。我偶尔遇到了几次**Windows更新不能工作**的情况。我选择安装更新而且Windows更新卡在了0%和0KB上就像这样
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_Updates_stuck_at_zero.jpeg)
本教程中我们会让Windows更新再次可用。这个教程应该同样适用于Windows 7、Windows 8和Windows 8.1。
### 修复Windows更新卡在0% ###
请注意Windows更新可能卡在任何地方我们将会使用的这个技巧需要你重新安装这些更新。我希望你不要觉得太麻烦。如果你准备好了就让我们开始修复这个Windows更新问题。
#### 步骤 1: ####
按下Windows+R。这时会弹出运行窗口。在这里我们输入services.msc
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Updates_3.png)
#### 步骤 2: ####
这里会显示Windows上安装的所有服务。这些服务以字母排序。向下拉到**Windows Update Service**。右击并停止服务。
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_Updates_stuck_1.jpeg)
#### 步骤 3: ####
现在进入**C:\Windows\SoftwareDistribution并删除这里所有的内容**。实际上这个文件夹是下载和保存安装文件的地方。但是由于Windows更新卡住了所以这里的某个安装文件存在一些问题。
#### 步骤 4: ####
回到前面的服务第一步中提到的并右击重新启动Windows更新服务。再重新试一下Windows更新这次应该可以用了。
当系统更新可以工作时,你或许会发现在下次启动时会有很多更新要安装。这时打个电话:
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/03/Windows_update_suck.jpg)
玩笑之余我希望这个贴士能够帮助你拜托Windows更新卡在0%的情况。我希望Linux中的更新也能够含在[Windows 10从Linux复制的特性][2]列表中。这只是我的希望。
--------------------------------------------------------------------------------
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Linux Basics: How To Fix “E: /var/cache/apt/archives/ subprocess new pre-removal script returned error exit status 1″ In Ubuntu
Linux 基础如何修复Ubuntu上“E: /var/cache/apt/archives/ subprocess new pre-removal script returned error exit status 1 ”的错误
================================================================================
![](https://1102047360.rsc.cdn77.org/wp-content/uploads/2014/04/ubuntu-790x558.png)
Today, I got a problem while updating VirtualBox to the latest version.
今天我在更新VirtualBox新版本的时候遇到了一个问题。
> E: /var/cache/apt/archives/ subprocess new pre-removal script returned error exit status 1
![](https://www.unixmen.com/wp-content/uploads/2015/03/Update-Manager_0011.png)
### Solution: ###
### 解决: ###
I googled a bit and found the solution. Here is what I did to solve the problem.
我google了以下并找到了方法。下面是我解决的方法。
sudo apt-get clean
sudo apt-get update && sudo apt-get upgrade
This will almost fix the problem.
这样几乎可以修复这个问题了。
If you still end up with the same error, then try the following commands:
如果你仍然有问题,那就试试下面的命令:
sudo dpkg --configure -a
sudo apt-get -f install
Or, you can manually download the latest version from [Oracle VirtualBox][1] site and install it as shown below.
或者你可以按照下面的方法从[Oracle VirtualBox][1]官网下载最新版本并安装。
sudo apt-get update
sudo dpkg -i virtualbox-4.3_4.3.24-98716~Ubuntu~raring_amd64.deb
sudo apt-get -f install
sudo apt-get autoclean && sudo apt-get autoremove
Cheers!
干杯!
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使用Observium来监控你的网络和服务器
================================================================================
### 简介###
在监控你的服务器,交换机或者物理机器时有过问题吗?, **Observium**可以满足你的需求.作为一个免费的监控系统,可以帮助你远程监控你的服务器.它是一个由PHP编写的基于自动发现SNMP的网络监控平台,支持非常广泛的网络硬件和操作系统,包括 Cisco,Windows,Linux,HP,NetApp等.在此我会通过在Ubuntu12.04上设置一个**Observium**服务器的同时提供相应的步骤.
![](https://www.unixmen.com/wp-content/uploads/2015/03/Capture1.png)
目前存在两种不同的**observium**版本.
- Observium 社区版本是一个在QPL开源许可证下的免费工具,这个版本时对于较小部署的最好解决方案. 该版本每6个月得到一次安全性更新.
- 第2个版本是Observium Professional, 该版本在基于SVN的发布机制下的发行版. 会得到每日安全性更新. 该工具适用于服务提供商和企业级部署.
更多信息可以通过其官网获得[website of Observium][1].
### 系统需求###
为了安装 **Observium**, 需要具有一个最新安装的服务器。**Observium**是在Ubuntu LTS和Debian系统上进行开发的所以推荐在Ubuntu或Debian上安装**Observium**,因为可能在别的平台上会有一些小问题。
该文章会知道你如何在Ubuntu12.04上进行安装**Observium**。对于小型的**Observium**安装推荐的基础配置要有256MB内存和双核处理器。
### 安装需求 ###
在安装**Observuim**之前,你需要确认安装所有的依赖关系包。
首先,使用下面的命令更新的服务器:
sudo apt-get update
然后你需要安装运行Observuim 所需的全部包。
Observium需要使用下面所列出的软件才能正确的运行
- LAMP server
- fping
- Net-SNMP 5.4+
- RRDtool 1.3+
- Graphviz
对于可选特性的要求:
- Ipmitool - 只有当你想要探寻IPMIIntelligent Platform Management Interface智能平台管理接口基板控制器。
- Libvirt-bin - 只有当你想要使用libvirt进行远程VM主机监控时。
sudo apt-get install libapache2-mod-php5 php5-cli php5-mysql php5-gd php5-mcrypt php5-json php-pear snmp fping mysql-server mysql-client python-mysqldb rrdtool subversion whois mtr-tiny ipmitool graphviz imagemagick libvirt ipmitool
### 为Observium创建MySQL 数据库和用户。
现在你需要登录到MySQL中并为**Observium**创建数据库:
mysql -u root -p
在用户验证成功之后,你需要按照下面的命令创建该数据库。
CREATE DATABASE observium;
数据库名为**Observium**,稍后你会需要这个信息。
现在你需要创建数据库管理员用户。
CREATE USER observiumadmin@localhost IDENTIFIED BY 'observiumpassword';
接下来,你需要给该管理员用户相应的权限来管理创建的数据库。
GRANT ALL PRIVILEGES ON observium.* TO observiumadmin@localhost;
你需要将权限信息写回到磁盘中来激活新的MySQL用户
FLUSH PRIVILEGES;
exit
### 下载并安装 Observium###
现在我们的系统已经准备好了, 可以开始Observium的安装了。
第一步创建Observium将要使用的文件目录
mkdir -p /opt/observium && cd /opt
为了达到本教程的目的我们将会使用Observium的社区/开源版本。使用下面的命令下载并解压:
wget http://www.observium.org/observium-community-latest.tar.gz
tar zxvf observium-community-latest.tar.gz
现在进入到Observium目录。
cd observium
将默认的配置文件'**config.php.default**'复制到'**config.php**',并将数据库配置选项填充到配置文件中:
cp config.php.default config.php
nano config.php
----------
/ Database config
$config['db_host'] = 'localhost';
$config['db_user'] = 'observiumadmin';
$config['db_pass'] = 'observiumpassword';
$config['db_name'] = 'observium';
现在为MySQL数据库设置默认的数据库模式
php includes/update/update.php
现在你需要创建一个文件目录来存储rrd文件并修改其权限以便让apache能将写入到文件中。
mkdir rrd
chown apache:apache rrd
为了在出现问题时进行问题修理,你需要创建日志文件。
mkdir -p /var/log/observium
chown apache:apache /var/log/observium
现在你需要为Observium创建虚拟主机配置。
<VirtualHost *:80>
DocumentRoot /opt/observium/html/
ServerName observium.domain.com
CustomLog /var/log/observium/access_log combined
ErrorLog /var/log/observium/error_log
<Directory "/opt/observium/html/">
AllowOverride All
Options FollowSymLinks MultiViews
</Directory>
</VirtualHost>
下一步你需要让你的Apache服务器的rewrite(重写)功能生效。
为了让'mod_rewrite'生效,输入以下命令:
sudo a2enmod rewrite
该模块在下一次Apache服务重启之后就会生效。
sudo service apache2 restart
###配置Observium###
在登入网络接口之前你需要为Observium创建一个管理员账户级别10
# cd /opt/observium
# ./adduser.php admin adminpassword 10
User admin added successfully.
下一步为发现和探寻工作设置一个cron任务创建一个新的文件**/etc/cron.d/observium** 并在其中添加以下的内容。
33 */6 * * * root /opt/observium/discovery.php -h all >> /dev/null 2>&1
*/5 * * * * root /opt/observium/discovery.php -h new >> /dev/null 2>&1
*/5 * * * * root /opt/observium/poller-wrapper.py 1 >> /dev/null 2>&1
重载cron进程来获取系的人物实体。
# /etc/init.d/cron reload
好啦你已经完成了Observium服务器的安装拉 使用你的浏览器登录到**http://<Server IP>**,然后上路巴。
![](https://www.unixmen.com/wp-content/uploads/2015/03/Capture.png)
尽情享受吧!
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作者:[anismaj][a]
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Nmap--不只是邪恶.
================================================================================
如果SSH是系统管理员世界的"瑞士军刀"的话,那么Nmap就是一盒炸药. 炸药很容易被误用然后将你的双脚崩掉,但是也是一个很有威力的工具,能够胜任一些看似无法完成的任务.
大多数人想到Nmap时,他们想到的是扫描服务器,查找开放端口来实施工具. 然而,在过去的这些年中,同样的超能力在当你管理服务器或计算机遇到问题时变得难以置信的有用.无论是你试图找出在你的网络上有哪些类型的服务器使用了指定的IP地址,或者尝试锁定一个新的NAS设备,以及扫描网络等,都会非常有用.
图1显示了我的QNAP NAS的网络扫描.我使用该单元的唯一目的是为了NFS和SMB文件共享,但是你可以看到,它包含了一大堆大开大敞的端口.如果没有Nmap,很难发现机器到底在运行着什么玩意儿.
![](http://www.linuxjournal.com/files/linuxjournal.com/ufiles/imagecache/large-550px-centered/u1002061/11825nmapf1.jpg)
### 图1 网络扫描 ###
另外一个无法想象的用处是用它来扫描一个网络.你甚至根本不需要root的访问权限,而且你也可以非常容易地来指定你想要扫描的网络块,例如,输入:
nmap 192.168.1.0/24
上述命令会扫描我局部网络中全部的254个可用的IP地址,让我可以知道那个使可以Ping的,以及那些端口时开放的.如果你刚刚插入一片新的硬件,但是不知道它通过DHCP获取的IP地址,那么此时Nmap就是无价之宝. 例如,上述命令在我的网络中揭示了这个问题.
Nmap scan report for TIVO-8480001903CCDDB.brainofshawn.com (192.168.1.220)
Host is up (0.0083s latency).
Not shown: 995 filtered ports
PORT STATE SERVICE
80/tcp open http
443/tcp open https
2190/tcp open tivoconnect
2191/tcp open tvbus
9080/tcp closed glrpc
它不仅显示了新的Tivo单元,而且还告诉我那些端口是开放的. 由于它的可靠性,可用性以及黑色边框帽子的能力,Nmap获得了本月的 <<编辑推荐>>奖. 这不是一个新的程序,但是如果你是一个linux用户的话,你应该玩玩它.
--------------------------------------------------------------------------------
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作者:[Shawn Powers][a]
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