Getting ssh to execute a command in the background on target machine

I had this problem in a program I wrote a year ago -- turns out the answer is rather complicated. You'll need to use nohup as well as output redirection, as explained in the wikipedia artcle on nohup, copied here for your convenience.

Nohuping backgrounded jobs is for example useful when logged in via SSH, since backgrounded jobs can cause the shell to hang on logout due to a race condition [2]. This problem can also be overcome by redirecting all three I/O streams:

nohup myprogram > foo.out 2> foo.err < /dev/null &

This has been the cleanest way to do it for me:-

ssh -n -f user@host "sh -c 'cd /whereever; nohup ./whatever > /dev/null 2>&1 &'"

The only thing running after this is the actual command on the remote machine

Redirect fd's

Output needs to be redirected with &>/dev/null which redirects both stderr and stdout to /dev/null and is a synonym of >/dev/null 2>/dev/null or >/dev/null 2>&1.

Parantheses

The best way is to use sh -c '( ( command ) & )' where command is anything.

ssh askapache 'sh -c "( ( nohup chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'

Nohup Shell

You can also use nohup directly to launch the shell:

ssh askapache 'nohup sh -c "( ( chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'

Nice Launch

Another trick is to use nice to launch the command/shell:

ssh askapache 'nice -n 19 sh -c "( ( nohup chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'