In this guide, we shall explain a basic but significant concept related to process handling in Linux systems—how to fully separate a process from its controlling terminal.

When a Linux process is linked to a terminal, two issues may occur:

1. Your terminal gets flooded with output and error/diagnostic messages.
2. If the terminal is closed, the process and any child processes will be terminated.

To avoid these problems, you need to completely disconnect a process from its controlling terminal. Before we proceed to the solution, let’s quickly go over how to run processes in the background on Linux.

Table of Contents

If a process is already running, such as the tar command example below, press Ctrl Z to pause it, then use the bg command to resume execution in the background as a background job.

You can check all your background jobs by entering the jobs command. However, its stdin, stdout, and stderr are still connected to the terminal.

<code>$ tar -czf home.tar.gz .
$ bg
$ jobs</code>

Alternatively, you can start a process in the background directly using the ampersand symbol &.

<code>$ tar -czf home.tar.gz . &
$ jobs</code>

As shown in the example below, even though the tar command was started in the background, an error message still appeared in the terminal, indicating that the process remains tied to the controlling terminal.

<code>$ tar -czf home.tar.gz . &
$ jobs
<p><strong>tar: ./.config/etcher: Cannot open: Permission denied</strong></p></code>

Keep Linux Process Running After Logout

The disown command can be used after a process has been started and sent to the background. It removes a shell job from the active job list so that commands like fg and bg can no longer control it.

Additionally, when the terminal is closed or the session ends, the process won’t receive a SIGHUP signal and will continue running.

Let's look at an example of using the disown bash built-in command.

<code>$ sudo rsync Templates/<em> /var/www/html/files/ &
$ jobs
$ disown  -h  %1
$ jobs</em></code>

Another option is the nohup command, which allows a process to keep running even after the user logs out.

<code>$ nohup tar -czf iso.tar.gz Templates/ &
$ jobs</code>

You might also like:

• 5 Ways to Keep Remote SSH Sessions and Processes Running After Closing Connection
• How to Limit Time and Memory Usage of Processes in Linux
• How to Monitor Running Linux Processes Using Top Command
• All You Need To Know About Processes in Linux [Comprehensive Guide]

Detach a Linux Process From Terminal

To completely detach a process from a controlling terminal, use the following format. This method works especially well for graphical applications (GUI) such as Firefox:

<code>$ firefox /null &>/dev/null &</code>

In Linux, /dev/null is a special file that discards any data written to it. In the above command, both input and output are redirected to /dev/null, effectively detaching the process from the terminal.

You might also like:

• How to Detach Linux Terminal Sessions Using Screen Command
• How to List Linux Running Processes with Their PIDs

To summarize, if a process remains attached to a controlling terminal, you may see numerous lines of output and error messages in your terminal window. Furthermore, closing the terminal will terminate the process and any associated child processes.

Please feel free to leave your comments or questions in the section below if you have anything to ask or share regarding this topic.

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