Home / ubuntu / Questions / 349262
Accepted
Steve Bennett
Asked: 2013-09-24 14:53:45 +0800 CST

Run a nohup command over SSH, then disconnect

  • 772

I want to execute a script, start.sh on a remote server which runs this:

nohup node server.js &

Naively, I call SSH like this:

ssh myserver <<EOF
./start.sh &
EOF

This starts the script, but leaves the session connected. I want to follow this step with other commands in a script, so that's no good.

How can I SSH to the remote machine, launch a nohup command into the background, then disconnect? I suppose I could put the SSH process itself into the background, but that doesn't seem right.

ssh

5 Answers

  1. Best Answer

    You have already found the right way, here document.

    NOTE: you can put the ssh (client) into background by placing a & at the end, but you will not see the output. If you really want to do this, redirect the stdout/stderr to a file in case you need to check the response from the remote host.

    Basically you can do it in either way:

    Directly run the command{,s}

    ssh user@host "nohup command1 > /dev/null 2>&1 &; nohup command2; command3"

    OR

    ssh user@host "$(nohup command1 > /dev/null 2>&1 &) && nohup command2 >> /path/to/log 2>&1 &"

    NOTE: && requires the first command to return 0 before executing the second

    Use Here document

    ssh user@host << EOF
nohup command1 > /dev/null 2>&1 &
nohup command2 >> /path/to/command2.log 2>&1 &
......
EOF

    The above 3 options should work for you.

    In addition, take a look at the answer here: https://askubuntu.com/a/348921/70270

    • 49 
  2. ssh node "nohup sleep 10 &"

    is not running in daemon mode, keeping your ssh session connected. Ssh session will return in 10 seconds, despite you used nohup.

    Reason is that remote stdout and stderr still connected to your session. It keeps ssh session alive, nohup does not help.

    This:

    ssh node "nohup sleep 10 1>/dev/null 2>/dev/null &"

    returns immediately. It does start remote process with nohup and exits ssh session immediately.

    • 15

  3. Why not just tmux or screen and be done with it? For example:

    $ tmux new -s SessionNameHere
$ nohup /path/to/your/script.sh

    This is practical if it's something that will continuously loop or take a while to finish. You can disconnect from the session and it will remain active.

    • 9

  4. Shorter form:

    ssh host "(command 1; command 2; ...) &>/dev/null &"

    It appears, that bash itself performs detaching from terminal, so no nohup needed. I run Ubuntu 14.04 x86_64, bash 4.3.11.

    • 5

  5. And last but not least, remember not to allocate a tty for your session.
    If you do that, it will not work.

    So if you got any -t or -tt or -ttt and so on in your command. Thats the reason why it is not working for you.

    So instead of

    ssh -tt host "(command 1; command 2; ...) &>/dev/null &"

    Use

    ssh host "(command 1; command 2; ...) &>/dev/null &"
    • 1