When you use the exec resources to run commands on the node, Puppet will give you an error message such as the following if a command returns a non-zero exit status:

Notice: /Stage[main]/Main/Exec[/bin/cat /tmp/missing]/returns: /bin/cat: /tmp/missing: No such file or directory
Error: /bin/cat /tmp/missing returned 1 instead of one of [0]
Error: /Stage[main]/Main/Exec[/bin/cat /tmp/missing]/returns: change from notrun to 0 failed: /bin/cat /tmp/missing returned 1 instead of one of [0]

As you can see, Puppet not only reports that the command failed, but shows its output:

/bin/cat: /tmp/missing: No such file or directory

This is useful to figure out why the command didn't work, but sometimes the command actually succeeds (in that it returns a zero exit status) but still doesn't do what we wanted. In that case, how can you see the command output? You can use the logoutput attribute.