ceph-mon fails for Ubuntu 12.04 in mon.pp

Below code in /etc/puppet/modules/ceph/manifests/mon.pp file fails for Ubuntu 12.04 .

mon_data=\$(ceph-mon ${cluster_option} --id ${id} --show-config-value mon_data)
if [ ! -d \$mon_data ] ; then
mkdir -p \$mon_data
if ceph-mon ${cluster_option} \
${public_addr_option} \
--mkfs \
--id ${id} \
--keyring ${keyring_path} ; then
touch \$mon_data/done \$mon_data/${init} \$mon_data/keyring
else
rm -fr \$mon_data
fi
fi

"ceph-mon ${cluster_option} --id ${id} --show-config-value mon_data" this line fails with Usage error.