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Useful Linux Commands that you should know
|
||||
======
|
||||
If you are Linux system administrator or just a Linux enthusiast/lover, than
|
||||
you love & use command line aks CLI. Until some years ago majority of Linux
|
||||
work was accomplished using CLI only & even there are some limitations to GUI
|
||||
. Though there are plenty of Linux distributions that can complete tasks with
|
||||
GUI but still learning CLI is major part of mastering Linux.
|
||||
|
||||
To this effect, we present you list of useful Linux commands that you should
|
||||
know.
|
||||
|
||||
**Note:-** There is no definite order to all these commands & all of these
|
||||
commands are equally important to learn & master in order to excel in Linux
|
||||
administration. One more thing, we have only used some of the options for each
|
||||
command for an example, you can refer to 'man pages' for complete list of
|
||||
options for each command.
|
||||
|
||||
### 1- top command
|
||||
|
||||
'top' command displays the real time summary/information of our system. It
|
||||
also displays the processes and all the threads that are running & are being
|
||||
managed by the system kernel.
|
||||
|
||||
Information provided by top command includes uptime, number of users, Load
|
||||
average, running/sleeping/zombie processes, CPU usage in percentage based on
|
||||
users/system etc, system memory free & used, swap memory etc.
|
||||
|
||||
To use top command, open terminal & execute the comamnd,
|
||||
|
||||
**$ top**
|
||||
|
||||
To exit out the command, either press 'q' or 'ctrl+c'.
|
||||
|
||||
### 2- free command
|
||||
|
||||
'free' command is used to specifically used to get the information about
|
||||
system memory or RAM. With this command we can get information regarding
|
||||
physical memory, swap memory as well as system buffers. It provided amount of
|
||||
total, free & used memory available on the system.
|
||||
|
||||
To use this utility, execute following command in terminal
|
||||
|
||||
**$ free**
|
||||
|
||||
It will present all the data in kb or kilobytes, for megabytes use options
|
||||
'-m' & '-g ' for gb.
|
||||
|
||||
#### 3- cp command
|
||||
|
||||
'cp' or copy command is used to copy files among the folders. Syntax for using
|
||||
'cp' command is,
|
||||
|
||||
**$ cp source destination**
|
||||
|
||||
### 4- cd command
|
||||
|
||||
'cd' command is used for changing directory . We can switch among directories
|
||||
using cd command.
|
||||
|
||||
To use it, execute
|
||||
|
||||
**$ cd directory_location**
|
||||
|
||||
### 5- ifconfig
|
||||
|
||||
'Ifconfig' is very important utility for viewing & configuring network
|
||||
information on Linux machine.
|
||||
|
||||
To use it, execute
|
||||
|
||||
**$ ifconfig**
|
||||
|
||||
This will present the network information of all the networking devices on the
|
||||
system. There are number of options that can be used with 'ifconfig' for
|
||||
configuration, in fact they are some many options that we have created a
|
||||
separate article for it ( **Read it here ||[IFCONFIG command : Learn with some
|
||||
examples][1]** ).
|
||||
|
||||
### 6- crontab command
|
||||
|
||||
'Crontab' is another important utility that is used schedule a job on Linux
|
||||
system. With crontab, we can make sure that a command or a script is executed
|
||||
at the pre-defined time. To create a cron job, run
|
||||
|
||||
**$ crontab -e**
|
||||
|
||||
To display all the created jobs, run
|
||||
|
||||
**$ crontab -l**
|
||||
|
||||
You can read our detailed article regarding crontab ( **Read it here ||[
|
||||
Scheduling Important Jobs with Crontab][2]** )
|
||||
|
||||
### 7- cat command
|
||||
|
||||
'cat' command has many uses, most common use is that it's used to display
|
||||
content of a file,
|
||||
|
||||
**$ cat file.txt**
|
||||
|
||||
But it can also be used to merge two or more file using the syntax below,
|
||||
|
||||
**$ cat file1 file2 file3 file4 > file_new**
|
||||
|
||||
We can also use 'cat' command to clone a whole disk ( **Read it here ||
|
||||
[Cloning Disks using dd & cat commands for Linux systems][3]** )
|
||||
|
||||
### 8- df command
|
||||
|
||||
'df' command is used to show the disk utilization of our whole Linux file
|
||||
system. Simply run.
|
||||
|
||||
**$ df**
|
||||
|
||||
& we will be presented with disk complete utilization of all the partitions on
|
||||
our Linux machine.
|
||||
|
||||
### 9- du command
|
||||
|
||||
'du' command shows the amount of disk that is being utilized by the files &
|
||||
directories on our Linux machine. To run it, type
|
||||
|
||||
**$ du /directory**
|
||||
|
||||
( **Recommended Read :[Use of du & df commands with examples][4]** )
|
||||
|
||||
### 10- mv command
|
||||
|
||||
'mv' command is used to move the files or folders from one location to
|
||||
another. Command syntax for moving the files/folders is,
|
||||
|
||||
**$ mv /source/filename /destination**
|
||||
|
||||
We can also use 'mv' command to rename a file/folder. Syntax for changing name
|
||||
is,
|
||||
|
||||
**$ mv file_oldname file_newname**
|
||||
|
||||
### 11- rm command
|
||||
|
||||
'rm' command is used to remove files\folders from Linux system. To use it, run
|
||||
|
||||
**$ rm filename**
|
||||
|
||||
We can also use '-rf' option with 'rm' command to completely remove a
|
||||
file\folder from the system but we must use this with caution.
|
||||
|
||||
### 12- vi/vim command
|
||||
|
||||
VI or VIM is very famous & one of the widely used CLI-based text editor for
|
||||
Linux. It takes some time to master it but it has a great number of utilities,
|
||||
which makes it a favorite for Linux users.
|
||||
|
||||
For detailed knowledge of VIM, kindly refer to the articles [**Beginner 's
|
||||
Guide to LVM (Logical Volume Management)** & **Working with Vi/Vim Editor :
|
||||
Advanced concepts.**][5]
|
||||
|
||||
### 13- ssh command
|
||||
|
||||
SSH utility is to remotely access another machine from the current Linux
|
||||
machine. To access a machine, execute
|
||||
|
||||
**$ ssh[[email protected]][6] OR machine_name**
|
||||
|
||||
Once we have remote access to machine, we can work on CLI of that machine as
|
||||
if we are working on local machine.
|
||||
|
||||
### 14- tar command
|
||||
|
||||
'tar' command is used to compress & extract the files\folders. To compress the
|
||||
files\folders using tar, execute
|
||||
|
||||
**$ tar -cvf file.tar file_name**
|
||||
|
||||
where file.tar will be the name of compressed folder & 'file_name' is the name
|
||||
of source file or folders. To extract a compressed folder,
|
||||
|
||||
**$ tar -xvf file.tar**
|
||||
|
||||
For more details on 'tar' command, read [**Tar command : Compress & Decompress
|
||||
the files\directories**][7]
|
||||
|
||||
### 15- locate command
|
||||
|
||||
'locate' command is used to locate files & folders on your Linux machines. To
|
||||
use it, run
|
||||
|
||||
**$ locate file_name**
|
||||
|
||||
### 16- grep command
|
||||
|
||||
'grep' command another very important command that a Linux administrator
|
||||
should know. It comes especially handy when we want to grab a keyword or
|
||||
multiple keywords from a file. Syntax for using it is,
|
||||
|
||||
**$ grep 'pattern' file.txt**
|
||||
|
||||
It will search for 'pattern' in the file 'file.txt' and produce the output on
|
||||
the screen. We can also redirect the output to another file,
|
||||
|
||||
**$ grep 'pattern' file.txt > newfile.txt**
|
||||
|
||||
### 17- ps command
|
||||
|
||||
'ps' command is especially used to get the process id of a running process. To
|
||||
get information of all the processes, run
|
||||
|
||||
**$ ps -ef**
|
||||
|
||||
To get information regarding a single process, executed
|
||||
|
||||
**$ ps -ef | grep java**
|
||||
|
||||
### 18- kill command
|
||||
|
||||
'kill' command is used to kill a running process. To kill a process we will
|
||||
need its process id, which we can get using above 'ps' command. To kill a
|
||||
process, run
|
||||
|
||||
**$ kill -9 process_id**
|
||||
|
||||
### 19- ls command
|
||||
|
||||
'ls' command is used list all the files in a directory. To use it, execute
|
||||
|
||||
**$ ls**
|
||||
|
||||
### 20- mkdir command
|
||||
|
||||
To create a directory in Linux machine, we use command 'mkdir'. Syntax for
|
||||
using 'mkdir' is
|
||||
|
||||
**$ mkdir new_dir**
|
||||
|
||||
These were some of the useful linux commands that every System Admin should
|
||||
know, we will soon be sharing another list of some more important commands
|
||||
that you should know being a Linux lover. You can also leave your suggestions
|
||||
and queries in the comment box below.
|
||||
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://linuxtechlab.com/useful-linux-commands-you-should-know/
|
||||
|
||||
作者：[][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://linuxtechlab.com
|
||||
[1]:http://linuxtechlab.com/ifconfig-command-learn-examples/
|
||||
[2]:http://linuxtechlab.com/scheduling-important-jobs-crontab/
|
||||
[3]:http://linuxtechlab.com/linux-disk-cloning-using-dd-cat-commands/
|
||||
[4]:http://linuxtechlab.com/du-df-commands-examples/
|
||||
[5]:http://linuxtechlab.com/working-vivim-editor-advanced-concepts/
|
||||
[6]:/cdn-cgi/l/email-protection#bbcec8dec9d5dad6defbf2ebdadfdfc9dec8c8
|
||||
[7]:http://linuxtechlab.com/tar-command-compress-decompress-files
|
||||
[8]:https://www.facebook.com/linuxtechlab/
|
||||
[9]:https://twitter.com/LinuxTechLab
|
||||
[10]:https://plus.google.com/+linuxtechlab
|
||||
[11]:http://linuxtechlab.com/contact-us-2/
|
||||
|
||||
@ -0,0 +1,77 @@
|
||||
Useful GNOME Shell Keyboard Shortcuts You Might Not Know About
|
||||
======
|
||||
As Ubuntu has moved to Gnome Shell in its 17.10 release, many users may be interested to discover some of the most useful shortcuts in Gnome as well as how to create your own shortcuts. This article will explain both.
|
||||
|
||||
If you expect GNOME to ship with hundreds or thousands of shell shortcuts, you will be disappointed to learn this isn't the case. The list of shortcuts isn't miles long, and not all of them will be useful to you, but there are still many keyboard shortcuts you can take advantage of.
|
||||
|
||||
![gnome-shortcuts-01-settings][1]
|
||||
|
||||
![gnome-shortcuts-01-settings][1]
|
||||
|
||||
To access the list of shortcuts, go to "Settings -> Devices -> Keyboard." Here are some less popular, yet useful shortcuts.
|
||||
|
||||
* Ctrl + Alt + T - this combination launches the terminal; you can use this from anywhere within GNOME
|
||||
|
||||
|
||||
|
||||
Two shortcuts I personally use quite frequently are:
|
||||
|
||||
* Alt + F4 - close the window on focus
|
||||
* Alt + F8 - resize the window
|
||||
|
||||
|
||||
Most of you know how to switch between open applications (Alt + Tab), but you may not know you can use Alt + Shift + Tab to cycle through applications in reverse direction.
|
||||
|
||||
Another useful combination for switching within the windows of an application is Alt + (key above Tab) (example: Alt + ` on a US keyboard).
|
||||
|
||||
If you want to show the Activities overview, use Alt + F1.
|
||||
|
||||
There are quite a lot of shortcuts related to workspaces. If you are like me and don't use multiple workspaces frequently, these shortcuts are useless to you. Still, some of the ones worth noting are the following:
|
||||
|
||||
* Super + PageUp (or PageDown) moves to the workspace above or below
|
||||
* Ctrl + Alt + Left (or Right) moves to the workspace on the left/right
|
||||
|
||||
If you add Shift to these commands, e.g. Shift + Ctrl + Alt + Left, you move the window one worskpace above, below, to the left, or to the right.
|
||||
|
||||
Another favorite keyboard shortcut of mine is in the Accessibility section - Increase/Decrease Text Size. You can use Ctrl + + (and Ctrl + -) to zoom text size quickly. In some cases, this may be disabled by default, so do check it out before you try it.
|
||||
|
||||
The above-mentioned shortcuts are lesser known, yet useful keyboard shortcuts. If you are curious to see what else is available, you can check [the official GNOME shell cheat sheet][2].
|
||||
|
||||
If the default shortcuts are not to your liking, you can change them or create new ones. You do this from the same "Settings -> Devices -> Keyboard" dialog. Just select the entry you want to change, and the following dialog will popup.
|
||||
|
||||
![gnome-shortcuts-02-change-shortcut][3]
|
||||
|
||||
![gnome-shortcuts-02-change-shortcut][3]
|
||||
|
||||
Enter the keyboard combination you want.
|
||||
|
||||
![gnome-shortcuts-03-set-shortcut][4]
|
||||
|
||||
![gnome-shortcuts-03-set-shortcut][4]
|
||||
|
||||
If it is already in use you will get a message. If not, just click Set, and you are done.
|
||||
|
||||
If you want to add new shortcuts rather than change existing ones, scroll down until you see the "Plus" sign, click it, and in the dialog that appears, enter the name and keys of your new keyboard shortcut.
|
||||
|
||||
![gnome-shortcuts-04-add-custom-shortcut][5]
|
||||
|
||||
![gnome-shortcuts-04-add-custom-shortcut][5]
|
||||
|
||||
GNOME doesn't come with tons of shell shortcuts by default, and the above listed ones are some of the more useful ones. If these shortcuts are not enough for you, you can always create your own. Let us know if this is helpful to you.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.maketecheasier.com/gnome-shell-keyboard-shortcuts/
|
||||
|
||||
作者：[Ada Ivanova][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:https://www.maketecheasier.com/author/adaivanoff/
|
||||
[1]https://www.maketecheasier.com/assets/uploads/2017/10/gnome-shortcuts-01-settings.jpg (gnome-shortcuts-01-settings)
|
||||
[2]https://wiki.gnome.org/Projects/GnomeShell/CheatSheet
|
||||
[3]https://www.maketecheasier.com/assets/uploads/2017/10/gnome-shortcuts-02-change-shortcut.png (gnome-shortcuts-02-change-shortcut)
|
||||
[4]https://www.maketecheasier.com/assets/uploads/2017/10/gnome-shortcuts-03-set-shortcut.png (gnome-shortcuts-03-set-shortcut)
|
||||
[5]https://www.maketecheasier.com/assets/uploads/2017/10/gnome-shortcuts-04-add-custom-shortcut.png (gnome-shortcuts-04-add-custom-shortcut)
|
||||
@ -0,0 +1,77 @@
|
||||
OnionShare - Share Files Anonymously
|
||||
======
|
||||
In this Digital World, we share our media, documents, important files via the Internet using different cloud storage like Dropbox, Mega, Google Drive and many more. But every cloud storage comes with two major problems, one is the Size and the other Security. After getting used to Bit Torrent the size is not a matter anymore, but the security is.
|
||||
|
||||
Even though you send your files through the secure cloud services they will be noted by the company, if the files are confidential, even the government can have them. So to overcome these problems we use OnionShare, as per the name it uses the Onion internet i.e Tor to share files Anonymously to anyone.
|
||||
|
||||
### How to Use **OnionShare**?
|
||||
|
||||
* First Download the [OnionShare][1] and [Tor Browser][2]. After downloading install both of them.
|
||||
|
||||
|
||||
|
||||
[![install onionshare and tor browser][3]][3]
|
||||
|
||||
* Now open OnionShare from the start menu
|
||||
|
||||
|
||||
|
||||
[![onionshare share files anonymously][4]][4]
|
||||
|
||||
* Click on Add and add a File/Folder to share.
|
||||
* Click start sharing. It produces a .onion URL, you could share the URL with your recipient.
|
||||
|
||||
|
||||
|
||||
[![share file with onionshare anonymously][5]][5]
|
||||
|
||||
* To Download file from the URL, copy the URL and open Tor Browser and paste it. Open the URL and download the Files/Folder.
|
||||
|
||||
|
||||
|
||||
[![receive file with onionshare anonymously][6]][6]
|
||||
|
||||
### Start of **OnionShare**
|
||||
|
||||
A few years back when Glenn Greenwald found that some of the NSA documents which he received from Edward Snowden had been corrupted. But he needed the documents and decided to get the files by using a USB. It was not successful.
|
||||
|
||||
After reading the book written by Greenwald, Micah Lee crypto expert at The Intercept, released the OnionShare - simple, free software to share files anonymously and securely. He created the program to share big data dumps via a direct channel encrypted and protected by the anonymity software Tor, making it hard to get the files for the eavesdroppers.
|
||||
|
||||
### How Does **OnionShare** Work?
|
||||
|
||||
OnionShare starts a web server at 127.0.0.1 for sharing the file on a random port. It chooses any of two words from the wordlist of 6800-wordlist called slug. It makes the server available as Tor onion service to send the file. The final URL looks like:
|
||||
|
||||
`http://qx2d7lctsnqwfdxh.onion/subside-durable`
|
||||
|
||||
The OnionShare shuts down after downloading. There is an option to allow the files to be downloaded multiple times. This makes the file not available on the internet anymore.
|
||||
|
||||
### Advantages of using **OnionShare**
|
||||
|
||||
Other Websites or Applications have access to your files: The file the sender shares using OnionShare is not stored on any server. It is directly hosted on the sender's system.
|
||||
|
||||
No one can spy on the shared files: As the connection between the users is encrypted by the Onion service and Tor Browser. This makes the connection secure and hard to eavesdroppers to get the files.
|
||||
|
||||
Both users are Anonymous: OnionShare and Tor Browser make both sender and recipient anonymous.
|
||||
|
||||
### Conclusion
|
||||
|
||||
In this article, I have explained how to **share your documents, files anonymously**. I also explained how it works. Hope you have understood how OnionShare works, and if you still have a doubt regarding anything, just drop in a comment.
|
||||
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.theitstuff.com/onionshare-share-files-anonymously-2
|
||||
|
||||
作者：[Anirudh Rayapeddi][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:https://www.theitstuff.com
|
||||
[1]https://onionshare.org/
|
||||
[2]https://www.torproject.org/projects/torbrowser.html.en
|
||||
[3]http://www.theitstuff.com/wp-content/uploads/2017/12/Icons.png
|
||||
[4]http://www.theitstuff.com/wp-content/uploads/2017/12/Onion-Share.png
|
||||
[5]http://www.theitstuff.com/wp-content/uploads/2017/12/With-Link.png
|
||||
[6]http://www.theitstuff.com/wp-content/uploads/2017/12/Tor.png
|
||||
@ -0,0 +1,93 @@
|
||||
The Biggest Problems With UC Browser
|
||||
======
|
||||
Before we even begin talking about the cons, I want to establish the fact that
|
||||
I have been a devoted UC Browser user for the past 3 years. I really love the
|
||||
download speeds I get, the ultra-sleek user interface and eye-catching icons
|
||||
used for tools. I was a Chrome for Android user in the beginning but I
|
||||
migrated to UC on a friend's recommendation. But in the past 1 year or so, I
|
||||
have seen some changes that have made me rethink about my choice and now I
|
||||
feel like migrating back to chrome again.
|
||||
|
||||
### The Unwanted **Notifications**
|
||||
|
||||
I am sure I am not the only one who gets these unwanted notifications every
|
||||
few hours. These clickbait articles are a real pain and the worst part is that
|
||||
you get them every few hours.
|
||||
|
||||
[![uc browser's annoying ads notifications][1]][1]
|
||||
|
||||
I tried closing them down from the notification settings but they still kept
|
||||
appearing with a less frequency.
|
||||
|
||||
### The **News Homepage**
|
||||
|
||||
Another unwanted section that is completely useless. We completely understand
|
||||
that UC browser is free to download and it may require funding but this is not
|
||||
the way to do it. The homepage features news articles that are extremely
|
||||
distracting and unwanted. Sometimes when you are in a professional or family
|
||||
environment some of these click baits might even cause awkwardness.
|
||||
|
||||
[![uc browser's embarrassing news homepage][2]][2]
|
||||
|
||||
And they even have a setting for that. To Turn the **UC** **News Display ON /
|
||||
OFF.** And guess what, I tried that too **.** In the image below, You can see
|
||||
my efforts on the left-hand side and the output on the right-hand side.[![uc
|
||||
browser homepage settings][3]][3]
|
||||
|
||||
And click bait news isn't enough, they have started adding some unnecessary
|
||||
features. So let's include them as well.
|
||||
|
||||
### UC **Music**
|
||||
|
||||
UC browser integrated a **music player** in their browser to play music. It 's
|
||||
just something that works, nothing too fancy. So why even have it? What's the
|
||||
point? Who needs a music player in their browsers?
|
||||
|
||||
[![uc browser adds uc music player][4]][4]
|
||||
|
||||
It's not even like it will play audio from the web directly via that player in
|
||||
the background. Instead, it is a music player that plays offline music. So why
|
||||
have it? I mean it is not even good enough to be used as a primary music
|
||||
player. Even if it was, it doesn't run independently of UC Browser. So why
|
||||
would someone have his/her browser running just to use your Music Player?
|
||||
|
||||
### The **Quick** Access Bar
|
||||
|
||||
I have seen 9 out of 10 average users have this bar hanging around in their
|
||||
notification area because it comes default with the installation and they
|
||||
don't know how to get rid of it. The settings on the right get the job done.
|
||||
|
||||
[![uc browser annoying quick access bar][5]][5]
|
||||
|
||||
But I still wanna ask, "Why does it come by default ?". It's a headache for
|
||||
most users. If we want it we will enable it. Why forcing the users though.
|
||||
|
||||
### Conclusion
|
||||
|
||||
UC browser is still one of the top players in the game. It provides one of the
|
||||
best experiences, however, I am not sure what UC is trying to prove by packing
|
||||
more and more unwanted features in their browser and forcing the user to use
|
||||
them.
|
||||
|
||||
I have loved UC for its speed and design. But recent experiences have led to
|
||||
me having a second thought about my primary browser.
|
||||
|
||||
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.theitstuff.com/biggest-problems-uc-browser
|
||||
|
||||
作者：[Rishabh Kandari][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:https://www.theitstuff.com/author/reevkandari
|
||||
[1]:http://www.theitstuff.com/wp-content/uploads/2017/10/Untitled-design-6.png
|
||||
[2]:http://www.theitstuff.com/wp-content/uploads/2017/10/Untitled-design-1-1.png
|
||||
[3]:http://www.theitstuff.com/wp-content/uploads/2017/12/uceffort.png
|
||||
[4]:http://www.theitstuff.com/wp-content/uploads/2017/10/Untitled-design-3-1.png
|
||||
[5]:http://www.theitstuff.com/wp-content/uploads/2017/10/Untitled-design-4-1.png
|
||||
|
||||
@ -1,90 +0,0 @@
|
||||
translating by lujun9972
|
||||
What Are Zombie Processes And How To Find & Kill Zombie Processes?
|
||||
======
|
||||
[][1]
|
||||
|
||||
If you are a regular Linux user, you must have encountered the term `Zombie Processes`. So what are the Zombie Processes? How do they get created? Are they harmful to the system? How do I kill these processes? Keep reading for the answers to all these questions.
|
||||
|
||||
### What are Zombie Processes?
|
||||
|
||||
So we all know how processes work. We launch a program, start our task & once our task is over, we end that process. Once the process has ended, it has to be removed from the processes table.
|
||||
|
||||
|
||||
|
||||
You can see the current processes in the ‘System-Monitor’.
|
||||
|
||||
[][2]
|
||||
|
||||
But, sometimes some of these processes stay in the processes table even after they have completed execution.
|
||||
|
||||
|
||||
|
||||
So these processes that have completed their life of execution but still exist in the processes table are called ‘Zombie Processes’.
|
||||
|
||||
### And How Exactly do they get Created?
|
||||
|
||||
Whenever we run a program it creates a parent process and a lot of child processes. All of these child processes use resources such as memory and CPU allocated to them by the kernel.
|
||||
|
||||
|
||||
|
||||
Once these child processes have finished executing they send an Exit call and die. This Exit call has to be read by the parent process which later calls the wait command to read the exit_status of the child process so that the child process can be removed from the processes table.
|
||||
|
||||
If the Parent reads the Exit call correctly sent by the Child Process, the process is removed from the processes table.
|
||||
|
||||
But, if the parent fails to read the exit call from the child process, the child process which has already finished its execution and is now dead will not be removed from the processes table.
|
||||
|
||||
### Are Zombie processes harmful to the System?
|
||||
|
||||
**No. **
|
||||
|
||||
Since zombie process is not doing any work, not using any resources or affecting any other process, there is no harm in having a zombie process. But since the exit_status and other process information from the process table are stored in the RAM, having too many Zombie processes can sometimes be an issue.
|
||||
|
||||
**_Imagine it Like this :_**
|
||||
|
||||
“
|
||||
|
||||
_You are the owner of a construction company. You pay daily wages to all your workers depending upon how they work. _ _A worker comes to the construction site every day, just sits there, you don’t have to pay him, he doesn’t do any work. _ _He just comes every day and sits, that’s it !”_
|
||||
|
||||
Such a worker is the living example of a zombie process.
|
||||
|
||||
**But,**
|
||||
|
||||
if you have a lot of zombie workers, your construction site will get crowded and it might get difficult for the people that are actually working.
|
||||
|
||||
### So how to find Zombie Processes?
|
||||
|
||||
Fire up a terminal and type the following command -
|
||||
|
||||
ps aux | grep Z
|
||||
|
||||
You will now get details of all zombie processes in the processes table.
|
||||
|
||||
### How to kill Zombie processes?
|
||||
|
||||
Normally we kill processes with the SIGKILL command but zombie processes are already dead. You Cannot kill something that is already dead. So what you do is you type this command -
|
||||
|
||||
kill -s SIGCHLD pid
|
||||
|
||||
Replace the pid with the id of the parent process so that the parent process will remove all the child processes that are dead and completed.
|
||||
|
||||
**_Imagine it Like this :_**
|
||||
|
||||
“
|
||||
|
||||
_You find a dead body in the middle of the road, you call the dead body’s family and they take that body away from the road.”_
|
||||
|
||||
But a lot of programs are not programmed well enough to remove these child zombies because if they were, you wouldn’t have those zombies in the first place. So the only thing guaranteed to remove Child Zombies is killing the parent.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.linuxandubuntu.com/home/what-are-zombie-processes-and-how-to-find-kill-zombie-processes
|
||||
|
||||
作者：[linuxandubuntu][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.linuxandubuntu.com
|
||||
[1]:http://www.linuxandubuntu.com/home/what-are-zombie-processes-and-how-to-find-kill-zombie-processes
|
||||
[2]:http://www.linuxandubuntu.com/uploads/2/1/1/5/21152474/linux-check-zombie-processes_orig.jpg
|
||||
@ -0,0 +1,78 @@
|
||||
什么是僵尸进程以及如何找到并杀掉僵尸进程？
|
||||
======
|
||||
[][1]
|
||||
|
||||
如果你经常使用 Linux，你应该遇到这个术语 `僵尸进程`。 那么什么是僵尸进程？ 它们是怎么产生的？ 他们是否对系统有害？ 我要怎样杀掉这些进程？ 下面将会回答这些问题。
|
||||
|
||||
### 什么是僵尸进程？
|
||||
|
||||
我们都知道进程的工作原理。我们启动一个程序，开始我们的任务，然后等任务结束了，我们就停止这个进程。 进程停止后， 该进程就会从进程表中移除。
|
||||
|
||||
你可以通过 `System-Monitor` 查看当前进程。
|
||||
|
||||
[][2]
|
||||
|
||||
但是，有时候有些程序即使执行完了也依然留在进程表中。
|
||||
|
||||
那么，这些完成了生命周期但却依然留在进程表中的进程，我们称之为 `僵尸进程`。
|
||||
|
||||
### 他们是如何产生的？
|
||||
|
||||
当你运行一个程序时，它会产生一个父进程以及很多子进程。 所有这些子进程都会消耗内核分配给他们的内存和 CPU 资源。
|
||||
|
||||
这些子进程完成执行后会发送一个 Exit 信号然后死掉。这个 Exit 信号需要被父进程所读取。父进程需要随后调用 `wait` 命令来读取子进程的退出状态并将子进程从进程表中移除。
|
||||
|
||||
若父进程正确第读取了子进程的 Exit 信号，则子进程会从进程表中删掉。
|
||||
|
||||
但若父进程未能读取到子进程的 Exit 信号，则这个子进程虽然完成执行处于死亡的状态，但也不会从进程表中删掉。
|
||||
|
||||
### 僵尸进程对系统有害吗 Are Zombie processes harmful to the System？
|
||||
|
||||
**不会**。由于僵尸进程并不做任何事情， 不会使用任何资源也不会影响其他进程， 因此存在僵尸进程也没什么坏处。 不过由于进程表中的退出状态以及其他一些进程信息也是存储在内存中的，因此存在太多僵尸进程有时也会是一些问题。
|
||||
|
||||
**你可以想象成这样:**
|
||||
|
||||
“你是一家建筑公司的老板。你每天根据工人们的工作量来支付工资。 有一个工人每天来到施工现场，就坐在那里， 你不用付钱， 它也不做任何工作。 他只是每天都来然后呆坐在那，仅此而已！”
|
||||
|
||||
这个工人就是僵尸进程的一个活生生的例子。**但是**， 如果你有很多僵尸工人， 你的建设工地就会很拥堵从而让那些正常的工人难以工作。
|
||||
|
||||
### 那么如何找出僵尸进程呢？
|
||||
|
||||
打开终端并输入下面命令:
|
||||
|
||||
```
|
||||
ps aux | grep Z
|
||||
```
|
||||
|
||||
会列出进程表中所有僵尸进程的详细内容。
|
||||
|
||||
### 如何杀掉僵尸进程？
|
||||
|
||||
正常情况下我们可以用 `SIGKILL` 信号来杀死进程，但是僵尸进程已经死了， 你不能杀死已经死掉的东西。 因此你需要输入的命令应该是
|
||||
|
||||
```
|
||||
kill -s SIGCHLD pid
|
||||
```
|
||||
|
||||
将这里的 pid 替换成父进程的 id，这样父进程就会删除所有以及完成并死掉的子进程了。
|
||||
|
||||
**你可以把它想象成:**
|
||||
|
||||
"你在道路中间发现一具尸体，于是你联系了死者的家属，随后他们就会将尸体带离道路了。"
|
||||
|
||||
不过许多程序写的不是那么好，无法删掉这些子僵尸(否则你一开始也见不到这些僵尸了)。 因此确保删除子僵尸的唯一方法就是杀掉它们的父进程。
|
||||
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.linuxandubuntu.com/home/what-are-zombie-processes-and-how-to-find-kill-zombie-processes
|
||||
|
||||
作者：[linuxandubuntu][a]
|
||||
译者：[lujun9972](https://github.com/lujun9972)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.linuxandubuntu.com
|
||||
[1]:http://www.linuxandubuntu.com/home/what-are-zombie-processes-and-how-to-find-kill-zombie-processes
|
||||
[2]:http://www.linuxandubuntu.com/uploads/2/1/1/5/21152474/linux-check-zombie-processes_orig.jpg
|
||||
Loading…
Reference in New Issue
Block a user