Logging command output

"Computer says no."—Little Britain

Detailed feedback on problems can be helpful. When you use exec resources to run commands on the node, it's not always easy to find out why they haven't worked. Puppet will give you an error message if a command returns a non-zero exit status. The error will be similar to the following:

err: /Stage[main]//Node[cookbook]/Exec[this-will-fail]/returns: change from notrun to 0 failed: /bin/ls file-that-doesnt-exist returned 2 instead of one of [0] at /etc/puppet/manifests/nodes.pp:10

Often we would like to see the actual output from the command that failed, rather than just the numerical exit status. You can do this with the logoutput parameter.

How to do it…

Define an exec resource with the logoutput parameter as follows:

exec { "this-will-fail":
    command   => "/bin/ls file-that-doesnt-exist",
    logoutput => on_failure,
}

How it works…

Now, if the command fails, Puppet will also print its output:

notice: /Stage[main]//Node[cookbook]/Exec[this-will-fail]/returns: /bin/ls: cannot access file-that-doesnt-exist: No such file or directory err: /Stage[main]//Node[cookbook]/Exec[this-will-fail]/returns: change from notrun to 0 failed: /bin/ls file-that-doesnt-exist returned 2 instead of one of [0] at /etc/puppet/manifests/nodes.pp:11

There's more…

You can set this to be the default for all exec resources by defining the following:

Exec {
    logoutput => on_failure,
}

If you want to see the command output whether it succeeds or fails, use the following:

logoutput => true,
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