How to set ssh timeout

Question

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

User · Answer

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

User · Answer

You could also connect with flag -o ServerAliveInterval  lt secs gt  so the SSH client will send a null packet to the server each  lt secs gt  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

User · Answer

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

User · Answer

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   gt   tmp outputfile 2 gt  amp 1  amp  PIDssh     Count 0  while test  Count -lt 5  amp  amp  ps -p  PIDssh  gt   dev null  do     echo -n       sleep 1     Count    Count 1    done  echo      if ps -p  PIDssh  gt   dev null  then     echo  ssh still running  killing it      kill -HUP  PIDssh  else     echo  Exited   fi

User · Answer

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

User · Answer

ssh -o ConnectTimeout 10   lt hostName gt    Where 10 is time in seconds   This Timeout applies only to the creation of the connection

[shell] How to set ssh timeout?

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