I need the process id of a process (here sleep 20) started remotely via SSH and sudo.
date is inserted to illustrate the duration of the SSH connection. Without connection there is also no process on my remote machine, of course.
$ date; ssh pc1 "sleep 20 & echo $!"; date # works Mi 20. Jan 16:18:29 CET 2016 11540 Mi 20. Jan 16:18:50 CET 2016 $ date; ssh pc1 "echo password | sudo -S sleep 20"; date # works Mi 20. Jan 16:20:44 CET 2016 [sudo] password for lab: Mi 20. Jan 16:21:04 CET 2016 $ date; ssh pc1 "echo password | sudo -S sleep 20 & echo $!"; date # does not Mi 20. Jan 16:21:55 CET 2016 11916 Mi 20. Jan 16:21:56 CET 2016
On a second machine the last, complete command works fine:
$ date; ssh pc2 "echo password | sudo -S sleep 20 & echo $!"; date Mi 20. Jan 16:23:40 CET 2016 6035 [sudo] password for lab: Mi 20. Jan 16:24:01 CET 2016
Any suggestion why there is this different behaviour of the two machines?
Info: I know the risk of clear passwords but it’s a shared account in an isolated test network.
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Answer
It looks like an issue with incomplete process dependencies. With some additional milliseconds the connection (and process) keeps established the whole time.
$ date; ssh pc1 "echo password | sudo -S sleep 20 & echo $! && sleep 0.01"; date Do 21. Jan 14:50:39 CET 2016 [sudo] password for lab: 6841 Do 21. Jan 14:51:00 CET 2016