Test environment is Ubuntu 14.04

This need install package 'sysv-rc-conf'
Disable Gerrit server from booting

# apt-get install sysv-rc-conf
# sysv-rc-conf --list
   ...
   gerrit       2:on
   ...
# sysv-rc-conf gerrit off
# sysv-rc-conf --list
   ...
   gerrit       2:off   3:off   4:off   5:off
   ...

Refer to above way, you can enable Gerrit.