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[Translated] tech/RHCE/Part 4 - Using Shell Scripting to Automate Linux System Maintenance Tasks.md
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ictlyh Translating
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Part 4 - Using Shell Scripting to Automate Linux System Maintenance Tasks
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================================================================================
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Some time ago I read that one of the distinguishing characteristics of an effective system administrator / engineer is laziness. It seemed a little contradictory at first but the author then proceeded to explain why:
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RHCE Series: Automate Linux System Maintenance Tasks – Part 4
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if a sysadmin spends most of his time solving issues and doing repetitive tasks, you can suspect he or she is not doing things quite right. In other words, an effective system administrator / engineer should develop a plan to perform repetitive tasks with as less action on his / her part as possible, and should foresee problems by using,
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for example, the tools reviewed in Part 3 – [Monitor System Activity Reports Using Linux Toolsets][1] of this series. Thus, although he or she may not seem to be doing much, it’s because most of his / her responsibilities have been taken care of with the help of shell scripting, which is what we’re going to talk about in this tutorial.
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### What is a shell script? ###
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In few words, a shell script is nothing more and nothing less than a program that is executed step by step by a shell, which is another program that provides an interface layer between the Linux kernel and the end user.
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By default, the shell used for user accounts in RHEL 7 is bash (/bin/bash). If you want a detailed description and some historical background, you can refer to [this Wikipedia article][2].
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To find out more about the enormous set of features provided by this shell, you may want to check out its **man page**, which is downloaded in in PDF format at ([Bash Commands][3]). Other than that, it is assumed that you are familiar with Linux commands (if not, I strongly advise you to go through [A Guide from Newbies to SysAdmin][4] article in **Tecmint.com** before proceeding). Now let’s get started.
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### Writing a script to display system information ###
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For our convenience, let’s create a directory to store our shell scripts:
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# mkdir scripts
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# cd scripts
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And open a new text file named `system_info.sh` with your preferred text editor. We will begin by inserting a few comments at the top and some commands afterwards:
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#!/bin/bash
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# Sample script written for Part 4 of the RHCE series
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# This script will return the following set of system information:
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# -Hostname information:
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echo -e "\e[31;43m***** HOSTNAME INFORMATION *****\e[0m"
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hostnamectl
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echo ""
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# -File system disk space usage:
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echo -e "\e[31;43m***** FILE SYSTEM DISK SPACE USAGE *****\e[0m"
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df -h
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echo ""
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# -Free and used memory in the system:
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echo -e "\e[31;43m ***** FREE AND USED MEMORY *****\e[0m"
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free
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echo ""
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# -System uptime and load:
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echo -e "\e[31;43m***** SYSTEM UPTIME AND LOAD *****\e[0m"
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uptime
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echo ""
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# -Logged-in users:
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echo -e "\e[31;43m***** CURRENTLY LOGGED-IN USERS *****\e[0m"
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who
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echo ""
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# -Top 5 processes as far as memory usage is concerned
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echo -e "\e[31;43m***** TOP 5 MEMORY-CONSUMING PROCESSES *****\e[0m"
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ps -eo %mem,%cpu,comm --sort=-%mem | head -n 6
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echo ""
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echo -e "\e[1;32mDone.\e[0m"
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Next, give the script execute permissions:
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# chmod +x system_info.sh
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and run it:
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./system_info.sh
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Note that the headers of each section are shown in color for better visualization:
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Server Monitoring Shell Script
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That functionality is provided by this command:
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echo -e "\e[COLOR1;COLOR2m<YOUR TEXT HERE>\e[0m"
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Where COLOR1 and COLOR2 are the foreground and background colors, respectively (more info and options are explained in this entry from the [Arch Linux Wiki][5]) and <YOUR TEXT HERE> is the string that you want to show in color.
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### Automating Tasks ###
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The tasks that you may need to automate may vary from case to case. Thus, we cannot possibly cover all of the possible scenarios in a single article, but we will present three classic tasks that can be automated using shell scripting:
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**1)** update the local file database, 2) find (and alternatively delete) files with 777 permissions, and 3) alert when filesystem usage surpasses a defined limit.
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Let’s create a file named `auto_tasks.sh` in our scripts directory with the following content:
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#!/bin/bash
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# Sample script to automate tasks:
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# -Update local file database:
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echo -e "\e[4;32mUPDATING LOCAL FILE DATABASE\e[0m"
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updatedb
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if [ $? == 0 ]; then
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echo "The local file database was updated correctly."
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else
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echo "The local file database was not updated correctly."
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fi
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echo ""
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# -Find and / or delete files with 777 permissions.
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echo -e "\e[4;32mLOOKING FOR FILES WITH 777 PERMISSIONS\e[0m"
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# Enable either option (comment out the other line), but not both.
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# Option 1: Delete files without prompting for confirmation. Assumes GNU version of find.
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#find -type f -perm 0777 -delete
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# Option 2: Ask for confirmation before deleting files. More portable across systems.
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find -type f -perm 0777 -exec rm -i {} +;
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echo ""
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# -Alert when file system usage surpasses a defined limit
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echo -e "\e[4;32mCHECKING FILE SYSTEM USAGE\e[0m"
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THRESHOLD=30
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while read line; do
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# This variable stores the file system path as a string
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FILESYSTEM=$(echo $line | awk '{print $1}')
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# This variable stores the use percentage (XX%)
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PERCENTAGE=$(echo $line | awk '{print $5}')
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# Use percentage without the % sign.
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USAGE=${PERCENTAGE%?}
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if [ $USAGE -gt $THRESHOLD ]; then
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echo "The remaining available space in $FILESYSTEM is critically low. Used: $PERCENTAGE"
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fi
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done < <(df -h --total | grep -vi filesystem)
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Please note that there is a space between the two `<` signs in the last line of the script.
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Shell Script to Find 777 Permissions
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### Using Cron ###
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To take efficiency one step further, you will not want to sit in front of your computer and run those scripts manually. Rather, you will use cron to schedule those tasks to run on a periodic basis and sends the results to a predefined list of recipients via email or save them to a file that can be viewed using a web browser.
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The following script (filesystem_usage.sh) will run the well-known **df -h** command, format the output into a HTML table and save it in the **report.html** file:
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#!/bin/bash
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# Sample script to demonstrate the creation of an HTML report using shell scripting
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# Web directory
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WEB_DIR=/var/www/html
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# A little CSS and table layout to make the report look a little nicer
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echo "<HTML>
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<HEAD>
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<style>
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.titulo{font-size: 1em; color: white; background:#0863CE; padding: 0.1em 0.2em;}
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table
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{
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border-collapse:collapse;
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}
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table, td, th
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{
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border:1px solid black;
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}
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</style>
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<meta http-equiv='Content-Type' content='text/html; charset=UTF-8' />
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</HEAD>
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<BODY>" > $WEB_DIR/report.html
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# View hostname and insert it at the top of the html body
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HOST=$(hostname)
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echo "Filesystem usage for host <strong>$HOST</strong><br>
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Last updated: <strong>$(date)</strong><br><br>
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<table border='1'>
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<tr><th class='titulo'>Filesystem</td>
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<th class='titulo'>Size</td>
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<th class='titulo'>Use %</td>
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</tr>" >> $WEB_DIR/report.html
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# Read the output of df -h line by line
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while read line; do
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echo "<tr><td align='center'>" >> $WEB_DIR/report.html
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echo $line | awk '{print $1}' >> $WEB_DIR/report.html
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echo "</td><td align='center'>" >> $WEB_DIR/report.html
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echo $line | awk '{print $2}' >> $WEB_DIR/report.html
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echo "</td><td align='center'>" >> $WEB_DIR/report.html
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echo $line | awk '{print $5}' >> $WEB_DIR/report.html
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echo "</td></tr>" >> $WEB_DIR/report.html
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done < <(df -h | grep -vi filesystem)
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echo "</table></BODY></HTML>" >> $WEB_DIR/report.html
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In our **RHEL 7** server (**192.168.0.18**), this looks as follows:
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Server Monitoring Report
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You can add to that report as much information as you want. To run the script every day at 1:30 pm, add the following crontab entry:
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30 13 * * * /root/scripts/filesystem_usage.sh
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### Summary ###
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You will most likely think of several other tasks that you want or need to automate; as you can see, using shell scripting will greatly simplify this effort. Feel free to let us know if you find this article helpful and don't hesitate to add your own ideas or comments via the form below.
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/using-shell-script-to-automate-linux-system-maintenance-tasks/
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作者：[Gabriel Cánepa][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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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]:http://www.tecmint.com/author/gacanepa/
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[1]:http://www.tecmint.com/linux-performance-monitoring-and-file-system-statistics-reports/
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[2]:https://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
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[3]:http://www.tecmint.com/wp-content/pdf/bash.pdf
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[4]:http://www.tecmint.com/60-commands-of-linux-a-guide-from-newbies-to-system-administrator/
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[5]:https://wiki.archlinux.org/index.php/Color_Bash_Prompt
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@ -0,0 +1,205 @@
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第四部分 - 使用 Shell 脚本自动化 Linux 系统维护任务
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================================================================================
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之前我听说高效系统管理员/工程师的其中一个特点是懒惰。一开始看起来很矛盾，但作者接下来解释了其中的原因：
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RHCE 系列：第四部分 - 自动化 Linux 系统维护任务
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如果一个系统管理员花费大量的时间解决问题以及做重复的工作，你就应该怀疑他这么做是否正确。换句话说，一个高效的系统管理员/工程师应该制定一个计划使得尽量花费少的时间去做重复的工作，以及通过使用该系列中第三部分 [使用 Linux 工具集监视系统活动报告][1] 介绍的工具预见问题。因此，尽管看起来他/她没有做很多的工作，但那是因为 shell 脚本帮助完成了他的/她的大部分任务，这也就是本章我们将要探讨的东西。
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### 什么是 shell 脚本？ ###
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简单的说，shell 脚本就是一个由 shell 一步一步执行的程序，而 shell 是在 Linux 内核和端用户之间提供接口的另一个程序。
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默认情况下，RHEL 7 中用户使用的 shell 是 bash（/bin/bash）。如果你想知道详细的信息和历史背景，你可以查看 [维基页面][2]。
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关于这个 shell 提供的众多功能的介绍，可以查看 **man 手册**，也可以从 （[Bash 命令][3]）下载 PDF 格式。除此之外，假设你已经熟悉 Linux 命令（否则我强烈建议你首先看一下 **Tecmint.com** 中的文章 [从新手到系统管理员指南][4] ）。现在让我们开始吧。
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### 写一个脚本显示系统信息 ###
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为了方便，首先让我们新建一个目录用于保存我们的 shell 脚本：
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# mkdir scripts
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# cd scripts
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然后用喜欢的文本编辑器打开新的文本文件 `system_info.sh`。我们首先在头部插入一些注释以及一些命令：
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#!/bin/bash
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# RHCE 系列第四部分事例脚本
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# 该脚本会返回以下这些系统信息：
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# -主机名称:
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echo -e "\e[31;43m***** HOSTNAME INFORMATION *****\e[0m"
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hostnamectl
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echo ""
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# -文件系统磁盘空间使用：
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echo -e "\e[31;43m***** FILE SYSTEM DISK SPACE USAGE *****\e[0m"
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df -h
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echo ""
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# -系统空闲和使用中的内存：
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echo -e "\e[31;43m ***** FREE AND USED MEMORY *****\e[0m"
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free
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echo ""
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# -系统启动时间：
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echo -e "\e[31;43m***** SYSTEM UPTIME AND LOAD *****\e[0m"
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uptime
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echo ""
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# -登录的用户：
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echo -e "\e[31;43m***** CURRENTLY LOGGED-IN USERS *****\e[0m"
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who
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echo ""
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# -使用内存最多的 5 个进程
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echo -e "\e[31;43m***** TOP 5 MEMORY-CONSUMING PROCESSES *****\e[0m"
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ps -eo %mem,%cpu,comm --sort=-%mem | head -n 6
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echo ""
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echo -e "\e[1;32mDone.\e[0m"
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然后，给脚本可执行权限：
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# chmod +x system_info.sh
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运行脚本：
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./system_info.sh
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注意为了更好的可视化效果各部分标题都用颜色显示：
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服务器监视 Shell 脚本
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该功能用以下命令提供：
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echo -e "\e[COLOR1;COLOR2m<YOUR TEXT HERE>\e[0m"
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其中 COLOR1 和 COLOR2 是前景色和背景色（[Arch Linux Wiki][5] 有更多的信息和选项解释），<YOUR TEXT HERE> 是你想用颜色显示的字符串。
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### 使任务自动化 ###
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你想使其自动化的任务可能因情况而不同。因此，我们不可能在一篇文章中覆盖所有可能的场景，但是我们会介绍使用 shell 脚本可以使其自动化的三种典型任务：
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**1)** 更新本地文件数据库， 2) 查找（或者删除）有 777 权限的文件， 以及 3) 文件系统使用超过定义的阀值时发出警告。
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让我们在脚本目录中新建一个名为 `auto_tasks.sh` 的文件并添加以下内容：
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#!/bin/bash
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# 自动化任务事例脚本：
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# -更新本地文件数据库：
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echo -e "\e[4;32mUPDATING LOCAL FILE DATABASE\e[0m"
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updatedb
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if [ $? == 0 ]; then
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echo "The local file database was updated correctly."
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else
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echo "The local file database was not updated correctly."
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fi
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echo ""
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# -查找 和/或 删除有 777 权限的文件。
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echo -e "\e[4;32mLOOKING FOR FILES WITH 777 PERMISSIONS\e[0m"
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# Enable either option (comment out the other line), but not both.
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# Option 1: Delete files without prompting for confirmation. Assumes GNU version of find.
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#find -type f -perm 0777 -delete
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# Option 2: Ask for confirmation before deleting files. More portable across systems.
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find -type f -perm 0777 -exec rm -i {} +;
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echo ""
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# -文件系统使用率超过定义的阀值时发出警告
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echo -e "\e[4;32mCHECKING FILE SYSTEM USAGE\e[0m"
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THRESHOLD=30
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while read line; do
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# This variable stores the file system path as a string
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FILESYSTEM=$(echo $line | awk '{print $1}')
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# This variable stores the use percentage (XX%)
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PERCENTAGE=$(echo $line | awk '{print $5}')
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# Use percentage without the % sign.
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USAGE=${PERCENTAGE%?}
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if [ $USAGE -gt $THRESHOLD ]; then
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echo "The remaining available space in $FILESYSTEM is critically low. Used: $PERCENTAGE"
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fi
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done < <(df -h --total | grep -vi filesystem)
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请注意该脚本最后一行两个 `<` 符号之间有个空格。
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查找 777 权限文件的 Shell 脚本
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### 使用 Cron ###
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想更进一步提高效率，你不会想只是坐在你的电脑前手动执行这些脚本。相反，你会使用 cron 来调度这些任务周期性地执行，并把结果通过邮件发动给预定义的接收者或者将它们保存到使用 web 浏览器可以查看的文件中。
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下面的脚本（filesystem_usage.sh）会运行有名的 **df -h** 命令，格式化输出到 HTML 表格并保存到 **report.html** 文件中：
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#!/bin/bash
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# Sample script to demonstrate the creation of an HTML report using shell scripting
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# Web directory
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WEB_DIR=/var/www/html
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# A little CSS and table layout to make the report look a little nicer
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echo "<HTML>
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<HEAD>
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<style>
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.titulo{font-size: 1em; color: white; background:#0863CE; padding: 0.1em 0.2em;}
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table
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{
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border-collapse:collapse;
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}
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table, td, th
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{
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border:1px solid black;
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}
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</style>
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<meta http-equiv='Content-Type' content='text/html; charset=UTF-8' />
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</HEAD>
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<BODY>" > $WEB_DIR/report.html
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# View hostname and insert it at the top of the html body
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HOST=$(hostname)
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echo "Filesystem usage for host <strong>$HOST</strong><br>
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Last updated: <strong>$(date)</strong><br><br>
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<table border='1'>
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<tr><th class='titulo'>Filesystem</td>
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<th class='titulo'>Size</td>
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||||
<th class='titulo'>Use %</td>
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</tr>" >> $WEB_DIR/report.html
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||||
# Read the output of df -h line by line
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while read line; do
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echo "<tr><td align='center'>" >> $WEB_DIR/report.html
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echo $line | awk '{print $1}' >> $WEB_DIR/report.html
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echo "</td><td align='center'>" >> $WEB_DIR/report.html
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||||
echo $line | awk '{print $2}' >> $WEB_DIR/report.html
|
||||
echo "</td><td align='center'>" >> $WEB_DIR/report.html
|
||||
echo $line | awk '{print $5}' >> $WEB_DIR/report.html
|
||||
echo "</td></tr>" >> $WEB_DIR/report.html
|
||||
done < <(df -h | grep -vi filesystem)
|
||||
echo "</table></BODY></HTML>" >> $WEB_DIR/report.html
|
||||
|
||||
在我们的 **RHEL 7** 服务器（**192.168.0.18**）中，看起来像下面这样：
|
||||
|
||||
|
||||
|
||||
服务器监视报告
|
||||
|
||||
你可以添加任何你想要的信息到那个报告中。添加下面的 crontab 条目在每天下午的 1：30 运行该脚本：
|
||||
|
||||
30 13 * * * /root/scripts/filesystem_usage.sh
|
||||
|
||||
### 总结 ###
|
||||
|
||||
你很可能想起各种其他想要自动化的任务；正如你看到的，使用 shell 脚本能极大的简化任务。如果你觉得这篇文章对你有所帮助就告诉我们吧，别犹豫在下面的表格中添加你自己的想法或评论。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/using-shell-script-to-automate-linux-system-maintenance-tasks/
|
||||
|
||||
作者：[Gabriel Cánepa][a]
|
||||
译者：[ictlyh](https://github.com/ictlyh)
|
||||
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.tecmint.com/author/gacanepa/
|
||||
[1]:http://www.tecmint.com/linux-performance-monitoring-and-file-system-statistics-reports/
|
||||
[2]:https://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
|
||||
[3]:http://www.tecmint.com/wp-content/pdf/bash.pdf
|
||||
[4]:http://www.tecmint.com/60-commands-of-linux-a-guide-from-newbies-to-system-administrator/
|
||||
[5]:https://wiki.archlinux.org/index.php/Color_Bash_Prompt
|
||||
Loading…
Reference in New Issue
Block a user