CODEWITHSUNDEEP
shellsshtimeout
user57421
user57421

Reputation: 7931

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?

Upvotes: 295

Views: 452325

Answers (8)

Danie
Danie

Reputation: 474

just adding the following .ssh/config snippet that I use,

  ServerAliveInterval 20
  ServerAliveCountMax 5
  ConnectTimeout 10

ConnectTimeout Specifies the timeout (in seconds) used when connecting to the SSH server, instead of using the default system TCP timeout. This timeout is applied both to establishing the connection and to performing the initial SSH protocol handshake and key exchange. (from the doc)

Upvotes: 6

Hanish Madan
Hanish Madan

Reputation: 57

timeout 5 ssh user@machine works for me.

Upvotes: 2

Eduardo
Eduardo

Reputation: 7851

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.

Upvotes: 0

user57421
user57421

Reputation: 7931

ssh -o ConnectTimeout=10  <hostName>

Where 10 is time in seconds. This Timeout applies only to the creation of the connection.

Upvotes: 469

Philip Kearns
Philip Kearns

Reputation: 419

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

Upvotes: 4

Patrizio Bertoni
Patrizio Bertoni

Reputation: 2732

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.

Upvotes: 31

Doug
Doug

Reputation: 3903

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.

Upvotes: 124

Lee HoYo
Lee HoYo

Reputation: 1267

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

Upvotes: 77

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