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# How to Start Linux Command in Background and Detach Process in Terminal
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In this guide, we shall bring to light a simple yet important concept in [process handling in a Linux system][8], that is how to completely detach a process from its controlling terminal.
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When a process is associated with a terminal, two problems might occur:
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1. your controlling terminal is filled with so much output data and error/diagnostic messages.
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2. in the event that the terminal is closed, the process together with its child processes will be terminated.
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To deal with these two issues, you need to totally detach a process from a controlling terminal. Before we actually move to solve the problem, let us briefly cover how to run processes in the background.
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### How to Start a Linux Process or Command in Background
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If a process is already in execution, such as the [tar command example][7] below, simply press `Ctrl+Z` to stop it then enter the command `bg` to continue with its execution in the background as a job.
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You can view all your background jobs by typing `jobs`. However, its stdin, stdout, stderr are still joined to the terminal.
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```
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$ tar -czf home.tar.gz .
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$ bg
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$ jobs
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```
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[][6]
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Run Linux Command in Background
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You can as well run a process directly from the background using the ampersand, `&` sign.
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```
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$ tar -czf home.tar.gz . &
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$ jobs
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```
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[][5]
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Start Linux Process in Background
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Take a look at the example below, although the [tar command][4] was started as a background job, an error message was still sent to the terminal meaning the process is still connected to the controlling terminal.
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```
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$ tar -czf home.tar.gz . &
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$ jobs
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```
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[][3]
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Linux Process Running in Background Message
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### Keep Linux Processes Running After Exiting Terminal
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We will use disown command, it is used after the a process has been launched and put in the background, it’s work is to remove a shell job from the shell’s active list jobs, therefore you will not use `fg`, `bg` commands on that particular job anymore.
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In addition, when you close the controlling terminal, the job will not hang or send a SIGHUP to any child jobs.
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Let’s take a look at the below example of using diswon bash built-in function.
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```
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$ sudo rsync Templates/* /var/www/html/files/ &
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$ jobs
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$ disown -h %1
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$ jobs
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```
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[][2]
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Keep Linux Process Running After Closing Terminal
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You can also use `nohup` command, which also enables a process to continue running in the background when a user exits a shell.
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```
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$ nohup tar -czf iso.tar.gz Templates/* &
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$ jobs
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```
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[][1]
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Put Linux Process in Background After Closing Shell
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### Detach a Linux Processes From Controlling Terminal
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Therefore, to completely detach a process from a controlling terminal, use the command format below, this is more effective for graphical user interface (GUI) applications such as firefox:
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```
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$ firefox </dev/null &>/dev/null &
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```
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In Linux, /dev/null is a special device file which writes-off (gets rid of) all data written to it, in the command above, input is read from, and output is sent to /dev/null.
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As a concluding remark, provided a process is connected to a controlling terminal, as a user, you will see several output lines of the process data as well as error messages on your terminal. Again, when you close the a controlling terminal, your process and child processes will be terminated.
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Importantly, for any questions or remarks on the subject, reach us by using the comment form below.
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/run-linux-command-process-in-background-detach-process/#
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作者：[Aaron Kili][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) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: http://www.tecmint.com/author/aaronkili/
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[1]:http://www.tecmint.com/wp-content/uploads/2016/10/Put-Linux-Process-in-Background.png
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[2]:http://www.tecmint.com/wp-content/uploads/2016/10/Keep-Linux-Processes-Running.png
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[3]:http://www.tecmint.com/wp-content/uploads/2016/10/Linux-Process-Running-in-Background-Message.png
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[4]:http://www.tecmint.com/18-tar-command-examples-in-linux/
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[5]:http://www.tecmint.com/wp-content/uploads/2016/10/Start-Linux-Process-in-Background.png
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[6]:http://www.tecmint.com/wp-content/uploads/2016/10/Run-Linux-Command-in-Background.png
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[7]:http://www.tecmint.com/18-tar-command-examples-in-linux/
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[8]:http://www.tecmint.com/monitor-linux-processes-and-set-process-limits-per-user/
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