This means you specified a source parameter for a file and Puppet couldn't find it. Check that the file is present and has been checked in, and also that the source path is correct.

This is often caused by Puppet trying to write a file to a directory that doesn't exist. Check that the directory either exists already or is defined in Puppet, and that the file resource require the directory (so that the directory is always created first).

This unhelpful error message is roughly translated as "something went wrong". It tends to be a catch-all error caused by many different problems, but you may be able to determine what is wrong from the name of the resource, the class, or the module. One trick is to add the --debug switch, to get more useful information:

# puppet agent --test --debug

If you check your Git history to see what was touched in the most recent change, this may be another way to identify what's upsetting Puppet.

This can be caused by mistyping command line options: for example, if you type puppet -verbose instead of puppet --verbose. That kind of error can be hard to see.

Either the node's SSL host key has changed, or Puppet's SSL directory has been deleted, or you are trying to request a certificate for a machine with the same name as an existing node. Generally, the simplest way to fix this is to remove Puppet's SSL directory from the client machine (usually this is /etc/puppet/ssl) and run puppet cert --clean <nodename> on the Puppetmaster. Then run Puppet again, and it should generate a certificate request correctly.

This usually indicates an error in compiling a template. You'll see this kind of error if you have a typo in your ERB syntax, such as in the following code snippet:

   rails_env <%!= app_env %>

This one has caused me some confusion in the past. Puppet's complaining about a duplicate definition, and normally if you have two resources with the same name, Puppet will helpfully tell you where they are both defined. But in this case, it's indicating the same file and line number for both. How can one resource be a duplicate of itself?

The answer is: if it's a define. If you create two instances of a define, you'll also have two instances of all the resources contained within the define, and they need to have distinct names. For example:

    define check_process() {
        exec { "is-process-running?":
            command => "/bin/ps ax |/bin/grep ${name} >/tmp/pslist.${name}.txt",
        }
    }

    check_process { "exim": }
    check_process { "nagios": }

# puppet agent --test
info: Retrieving plugin
err: Could not retrieve catalog from remote server: Error 400 on SERVER: Duplicate definition: Exec[is-process-running?] is already defined in file /etc/puppet/manifests/nodes.pp at line 22; cannot redefine at /etc/puppet/manifests/nodes.pp:22 on node cookbook.bitfieldconsulting.com
warning: Not using cache on failed catalog
err: Could not retrieve catalog; skipping run

Because the exec resource is named is-process-running? and this stays the same no matter what you pass to the define, Puppet will refuse to create two instances of it. The solution is to include the name of the instance in the title of each resource, as follows:

exec { "is-process-${name}-running?":
    command => "/bin/ps ax |/bin/grep ${name} >/tmp/pslist.${name}.txt",
}