process-detach.md

If you are running a command inside a Linux terminal (over SSH or otherwise), this command will normally be killed when you close the terminal session.

There is a way to have it survive the terminal and to come back to it later, even if the command is already running.

You'll need the screen and reptyr packages installed.

For the sake of example, let's have htop running.

$ htop

In a new terminal (for the same user), find the PID of htop (it's the 1st number)

$ ps aux|grep htop
john        9630  4.4  0.1   9356  5452 tty2     S+   22:03   0:56 htop
john        9683  0.0  0.0   6332  2024 pts/0    S+   22:24   0:00 grep htop

then start a screen session

$ screen

Inside the screen session, "bring over" htop by it's PID

$ reptyr 9630

Now it should be running right in front of us, in the screen session. On the old terminal (tty2) it would stop with a message at the bottom

1+  [Stopped]     htop

The new terminal which hosts the screen session can safely be killed. The screen session will persist and act as a virtual terminal for htop.

To go back to it, find the detached screen:

$ screen -ls
There is a screen on:
        9690.pts-0.debian       (09/29/2023 10:27:59 PM)        (Detached)
1 Socket in /run/screen/S-john.

and reattach it:

$ screen -r 9690.pts-0.debian