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Moving a currently running process to screen or tmux on Linux

Last Updated: [2023-03-29 Wed 07:06]

For all those "I should have f***ing done this in Screen!" moments every Linux SysAdmin Service Delivery agent goes through from time to time.

Firstly, ensure reptyr is installed. (More information about what reptyr is can be found on the project's GitHub page)

Let's say you're running a task on a Linux box (a Puppet run for example) either late in the day or late at night. And you suddenly remember you need to go home, or to bed, but then think "oh noes, this isn't running in screen!" You could either leave your machine at work (a no-go for on callers) or wait it out, writing a long essay on why Screen is the best thing since sliced bread to pass the time…

…Or you could do the following:

Press CTRL+Z to suspend the current running process.
Move the task to the background by running bg.
Get the PID of the process by running jobs -l. (Let's say the PID is 411)
Disown the job from the current session disown puppet (using puppet as the example here).
Start screen with the screen command. (Or you could use tmux if you like)
Reattach the process to the new terminal session with reptyr 411.

At this point, you should be able to close the whole connection to the box, and continue later by reconnecting and running screen -R. (or tmux attach)

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