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I have a process running on my Linux machine (Debian squeeze) that takes hours (or days) to finish.

I don't want to stop it to restart it again with screen, tmux or with an output redirect to nohup.

Is there a secure way to put it in the background with ^Z and bg so it will continue once I close the ssh-session?

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rubo77
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  • what do you mean by "stop it to restart it again with screen,tmux.."? if you start a tmux/scrn session via ssh, it will keep alive if you close your ssh connection. –  Oct 08 '12 at 13:29
  • the process is already running and lasting for some hours, but i cannot stop it or i will loose data. – rubo77 Oct 08 '12 at 14:46
  • If the command is already running, I don't think there's a way to accomplish this. There are, however, numerous ways to do it in the future if you run it under `screen`, `dtach`, `tmux`, etc. as you already note, or with appropriate redirections and `nohup`. You *might* be able to `^Z`, `bg` it now, but whether that's enough depends on whether it does I/O on the terminal after you background it. –  Oct 08 '12 at 14:58

1 Answers1

7

use

commandtoexecute &> /dev/null &

it will run your process in the background, and prints all output to /dev/null.

Replace /dev/null with another file to see the output.

e.g. commandtoexecute &> /tmp/file1 &

use tail -f /tmp/file1 to attach to output again

You can also redirect stdin, see this http://www.tuxfiles.org/linuxhelp/iodirection.html

If you want to detatch from a process that is allready running. Use disown <pid> where pid is your process id.

You could also change the terminal to another terminal:

  1. start a screen
  2. get pid of your process
  3. run reptyr <pid>
  4. detach using CTRL+A+D

reptyr: https://serverfault.com/a/284795

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  • I would add 2>&1 to see the error output too. – Dmytro Sirenko Oct 08 '12 at 14:04
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    &> redirects all output :D –  Oct 08 '12 at 14:05
  • thx, that would be the right start in the first place. But you didn't read my question: the process is already running and cannot be started over with your additions – rubo77 Oct 08 '12 at 14:47
  • ok, edited, check my answer –  Oct 08 '12 at 14:52
  • yes, thats the question: "detatch from a process that is allready running" ;) So `disown` would be your answer? Isn't there a problem then with stdout being detached? see http://unix.stackexchange.com/questions/39714/why-do-nohup-and-disown-not-work-on-sox-invoked-as-play – rubo77 Oct 08 '12 at 15:23
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    brings me to this: http://serverfault.com/a/284795, Start a screen, run reptyr with pid and detach –  Oct 08 '12 at 15:32
  • `disown` doesen't work: "bash: disown: 4219: Kein solcher Job." And reptyr is a bit strange: i get lots of messages and at the end "[+] Set the controlling tty" Does this mean, that it worked? – rubo77 Oct 08 '12 at 20:45
  • actually `reptyr` works fine: http://serverfault.com/a/284795 thanks! – rubo77 May 14 '13 at 17:35