[shell] How to set ssh timeout?

I'm executing a script connecting via password-less SSH on a remote host. I want to set a timeout, so that if the remote host is taking an infinite time to run, I want to come out of that ssh session and continue other lines in my sh script.

How can I set a timeout?

If all else fails (including not having the timeout command) the concept in this shell script will work:

 #!/bin/bash
 set -u
 ssh $1 "sleep 10 ; uptime" > /tmp/outputfile 2>&1 & PIDssh=$!
 Count=0
 while test $Count -lt 5 && ps -p $PIDssh > /dev/null
 do
    echo -n .
    sleep 1
    Count=$((Count+1))
 done
 echo ""

 if ps -p $PIDssh > /dev/null
 then
    echo "ssh still running, killing it"
    kill -HUP $PIDssh
 else
    echo "Exited"
 fi

try this:

timeout 5 ssh user@ip

timeout executes the ssh command (with args) and sends a SIGTERM if ssh doesn't return after 5 second. for more details about timeout, read this document: http://man7.org/linux/man-pages/man1/timeout.1.html

or you can use the param of ssh:

ssh -o ConnectTimeout=3 user@ip

Use the -o ConnectTimeout and -o BatchMode=yes -o StrictHostKeyChecking=no .

ConnectTimeout keeps the script from hanging, BatchMode keeps it from hanging with Host unknown, YES to add to known_hosts, and StrictHostKeyChecking adds the fingerprint automatically.

**** NOTE **** The "StrictHostKeyChecking" was only intended for internal networks where you trust you hosts. Depending on the version of the SSH client, the "Are you sure you want to add your fingerprint" can cause the client to hang indefinitely (mainly old versions running on AIX). Most modern versions do not suffer from this issue. If you have to deal with fingerprints with multiple hosts, I recommend maintaining the known_hosts file with some sort of configuration management tool like puppet/ansible/chef/salt/etc.

You could also connect with flag

-o ServerAliveInterval=<secs>

so the SSH client will send a null packet to the server each <secs> seconds, just to keep the connection alive. In Linux this could be also set globally in /etc/ssh/ssh_config or per-user in ~/.ssh/config.

Well, you could use nohup to run whatever you are running on 'non-blocking mode'. So you can just keep checking if whatever it was supposed to run, ran, otherwise exit.

nohup ./my-script-that-may-take-long-to-finish.sh &
./check-if-previous-script-ran-or-exit.sh

echo "Script ended on Feb 15, 2011, 9:20AM" > /tmp/done.txt

So in the second one you just check if the file exists.