Does losing an ssh session kills commands running in tmux?

Question

The question I know is basic, but could not find an exact matching question in community.
The standard process of using tmux is - create a session, run command within and then detach the session. So existing ssh terminal will not kill our process.

My question is, if tmux session is created and a long command is running within it. But before detaching, if ssh session terminates, then will this tmux session persist or it will be killed too?

Answer 1

Basically after losing an ssh connection the child process will receive a SIGHUP. This signal causes tmux to detach itself from the lossen ssh session.

So tmux's session will stay persistent on a remote machine even if ssh session gets terminated.

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Test it yourself:

1. Open a terminal and run tmux.
2. In your "tmux" session run sleep 100.
3. Open another terminal and run: pkill -1 tmux.
   • Now tmux has been closed in the first terminal.
4. Run tmux ls to see that your sessions is still there.
   • Or tmux attach to bring it up.

_{I have also tested the actual losing ssh session scenario on a remote machine, result is the same.}