Don't use exec without user parameter

If you use exec without user parameter, the command will get executed as root. You mostly don't want this.

There is a difference in the env variables of the exec if you run puppet manually or if the daemon runs.

Never ever use exec without cwd parameter

If you use exec without cwd parameter, the command get executed in the cwd of your puppet run. This can cause problems if you run the puppet agent manually.

Example:

# exec resource:
exec { "update_rubygems_${user}_${version}":
  command => "${home}/.rbenv/shims/gem update --system ${version}",
  unless  => "${home}/.rbenv/shims/gem -v | /bin/grep ${version}",
}

This does execute rbenv commands. If puppet runs in a cwd without .rbenv-version it's no problem it uses the default ruby version. If you are in a cwd with a .ruby-version it uses the ruby version from this file for all rbenv commands. You will probably get some errors.