dh_systemd_start man page
dh_systemd_start — start/stop/restart systemd unit files
dh_systemd_start [debhelper options] [--restart-after-upgrade] [--no-stop-on-upgrade] [unit file ...]
dh_systemd_start is a debhelper program that is responsible for starting/stopping or restarting systemd unit files in case no corresponding sysv init script is available.
As with dh_installinit, the unit file is stopped before upgrades and started afterwards (unless --restart-after-upgrade is specified, in which case it will only be restarted after the upgrade). This logic is not used when there is a corresponding SysV init script because invoke-rc.d performs the stop/start/restart in that case.
Do not stop the unit file until after the package upgrade has been completed. This is the default behaviour in compat 10.
In earlier compat levels the default was to stop the unit file in the prerm, and start it again in the postinst.
This can be useful for daemons that should not have a possibly long downtime during upgrade. But you should make sure that the daemon will not get confused by the package being upgraded while it's running before using this option.
Undo a previous --restart-after-upgrade (or the default of compat 10). If no other options are given, this will cause the service to be stopped in the prerm script and started again in the postinst script.
- -r, --no-stop-on-upgrade, --no-restart-on-upgrade
Do not stop service on upgrade.
Do not start the unit file after upgrades and after initial installation (the latter is only relevant for services without a corresponding init script).
Note that this command is not idempotent. dh_prep(1) should be called between invocations of this command (with the same arguments). Otherwise, it may cause multiple instances of the same text to be added to maintainer scripts.
Note that dh_systemd_start should be run after dh_installinit so that it can detect corresponding SysV init scripts. The default sequence in dh does the right thing, this note is only relevant when you are calling dh_systemd_start manually.