gistfile1.txt

[root@host ~]# test `ls -1 /dev/iscsi* | wc -l` -eq 0
[root@host ~]# echo $?
1

class iscsi
    ...
    file{'/etc/iscsi/iscsid.conf':
        content => template('iscsi/iscsid.conf.erb'),
        require => Package['iscsi-initiator-utils'],
        notify => [
            Exec[update_iscsi_database],
            Exec[restart_iscsi_daemon_before_discovery],
            Exec[discover_iscsi_targets],
        ],
        owner => root, group => 0, mode => 0600;
    }
    exec{'restart_iscsi_daemon_before_discovery':
        refreshonly => true,
        before => Exec[discover_iscsi_targets],
        onlyif => "test `ls -1 /dev/iscsi* | wc -l` -eq 0",
        command => "/etc/init.d/iscsi restart; /bin/true",
    }
    ...
}