Ssh Script Returns 255 Error

pkill returns 255 in combination with another command via remote ssh

The documentation for the pkill -f option says:

-f

The pattern is normally only matched against the process name. When -f is set, the full command line is used.

So pkill -f xyz will kill any process with "xyz" anywhere on its command line.

When you run ssh <remoteHost> 'source /etc/profile; pkill -f xyz', the remote ssh server will run the equivalent of this on your behalf:

$SHELL -c 'source /etc/profile; pkill -f xyz'

The resulting shell instance is a process with "xyz" in its command line. My guess is that pkill is killing it, and ssh is reporting the killed session as exit code 255, like this:

$ ssh localhost 'kill $$'
$ echo $?
255

It doesn't happen when you just run ssh <remoteHost> 'pkill -f xyz', because some shells like bash will optimize for this case. Instead of running pkill as a subprocess, the shell instance will replace itself with the pkill process. So by the time pkill runs, the shell process with "xyz" on its command line is gone.

You can probably work around this by running pkill like this:

ssh <remoteHost> 'source /etc/profile; exec pkill -f xyz'

If that doesn't work, you can specify the pkill pattern in such a way that it doesn't match the pattern itself. For example:

ssh <remoteHost> 'source /etc/profile; exec pkill -f "[x]yz"'

The pattern [x]yz matches the text "xyz", so pkill will kill processes where the text "xyz" appears. But the pattern doesn't match itself, so pkill won't kill processes where the pattern appears.

Jenkins, Host key verification failed, script returned exit code 255

It seems that the solution was to add the parameter StrictHostKeyChecking to the shell script line

sh "ssh -o StrictHostKeyChecking=no user@product.company.com 'echo $HOME'"

Exit codes 127 and 255 in Robot Framework

To execute commands that are not built-in. Directly write them to the terminal using "Write" keyword.

Use Write keyword in SSHLibrary. It pastes the command on the terminal and the command gets executed.

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