选题: 20200525 How to Execute a Command or Script at Reboot or Startup

sources/tech/20200525 How to Execute a Command or Script at Reboot or Startup.md

sources/tech/20200525 How to Execute a Command or Script at Reboot or Startup.md

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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (How to Execute a Command or Script at Reboot or Startup)
+[#]: via: (https://www.2daygeek.com/execute-run-linux-scripts-command-at-reboot-startup/)
+[#]: author: (Magesh Maruthamuthu https://www.2daygeek.com/author/magesh/)
+
+How to Execute a Command or Script at Reboot or Startup
+======
+
+Well known services on Linux can be added on boot without any problems.
+
+For example, if you want to add Apache Httpd **[service on boot][1]**, you can do this with the help of the chkconfig and systemctl command.
+
+Sometimes you need to add a custom script or command or service on boot, and how to do it?
+
+You can do this using the below three methods.
+
+In this article, we will show you how to use these methods with examples.
+
+### Method-1: How to Run Script or Command at Reboot or Startup Using /etc/rc.d/rc.local File
+
+The **“/etc/rc.local”** file is traditionally executed after all normal computer services have been started at the end of the process of switching to a multiuser runlevel.
+
+This method also works on the systemd system.
+
+You need to add the location of your script to the “/etc/rc.d/rc.local” file to run on boot.
+
+Make sure the file has permission to run.
+
+```
+# chmod +x /etc/rc.d/rc.local
+```
+
+To demonstrate this, we are going to create a simple sample script. You can create any script as needed.
+
+```
+# vi /opt/scripts/run-script-on-boot.sh
+
+#!/bin/bash
+date > /root/on-boot-output.txt
+hostname > /root/on-boot-output.txt
+```
+
+Once the script is ready, set the executable permission.
+
+```
+# chmod +x /opt/scripts/run-script-on-boot.sh
+```
+
+Finally add the script to the bottom of the file.
+
+```
+# vi /etc/rc.d/rc.local
+
+/opt/scripts/run-script-on-boot.sh
+```
+
+**[Restart your system][2]** to check this.
+
+```
+# reboot
+```
+
+### Method-2: How to Execute a Command or Script at Reboot or Startup Using the crontab
+
+cron executes scheduled jobs automatically in the backend at a specific time.
+
+This can be easily accomplished using a special string called **“@reboot”** with **[cron job][3]**.
+
+@reboot is a special string and allows the user to run any command or script at startup (boot time).
+
+This example runs the “/opt/scripts/run-script-on-boot.sh” file on the system restart.
+
+We are going to use the same script as above.
+
+To do so, just add the following entry in the crontab file.
+
+```
+# crontab -e
+
+@reboot /opt/scripts/run-script-on-boot.sh
+```
+
+Restart your system to check this.
+
+```
+# reboot
+```
+
+### Method-3: How to Run a Command or Script at Reboot or Startup Using the systemd service unit
+
+This method only works on the systemd system. This method is very straightforward.
+
+We are going to use the same script above to demonstrate this.
+
+To do so, you need to create a systemd startup script and place it in the **“/etc/systemd/system/”** directory.
+
+This is our sample systemd startup unit script.
+
+```
+# vi sample-on-boot-script.service
+
+[Unit]
+Description=Run a Custom Script at Startup
+After=default.target
+
+[Service]
+ExecStart=/opt/scripts/run-script-on-boot.sh
+
+[Install]
+WantedBy=default.target
+```
+
+Once you place the unit script in the systemd location, run the following command to update the systemd configuration files and enable the service.
+
+```
+# systemctl daemon-reload
+# systemctl enable sample-on-boot-script.service
+```
+
+Restart your system to check this.
+
+```
+# reboot
+```
+
+### Bonus Tips:
+
+If you want to run a script in the background, you need to add the trailing ampersand “&” symbol.
+
+```
+/Path/To/My_Script &
+```
+
+If you want to run the command as a different user, use the following format.
+
+```
+su - $USER -c /Path/To/My_Script
+```
+
+--------------------------------------------------------------------------------
+
+via: https://www.2daygeek.com/execute-run-linux-scripts-command-at-reboot-startup/
+
+作者：[Magesh Maruthamuthu][a]
+选题：[lujun9972][b]
+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.2daygeek.com/author/magesh/
+[b]: https://github.com/lujun9972
+[1]: https://www.2daygeek.com/enable-disable-services-on-boot-linux-chkconfig-systemctl-command/
+[2]: https://www.2daygeek.com/6-commands-to-shutdown-halt-poweroff-reboot-the-linux-system/
+[3]: https://www.2daygeek.com/linux-crontab-cron-job-to-schedule-jobs-task/