This plugin must be run as the same user that BackupPC runs under.  For a host 
to be considered an archive host by the --backup-only and --archive-only options
at least one archive must be run by the host.

Sample configuration for NRPE with Ubuntu hosts:
1) Add the following line to /etc/sudoers on the backup host
  nagios ALL = (backuppc) NOPASSWD: /usr/local/lib/nagios/plugins/check_backuppc

2) Add the following line to /etc/nagios/nrpe.cfg
  command[check_backuppc]=/usr/bin/sudo -u backuppc \
    /usr/local/lib/nagios/plugins/check_backuppc

3) Add the appropriate stanza to your Nagios configuration to use this check
   with NRPE.