kazulog@sv1:~$ sudo systemctl mask nginx
Created symlink '/etc/systemd/system/nginx.service' → '/dev/null'.
kazulog@sv1:~$ systemctl is-enabled nginx
masked
kazulog@sv1:~$ sudo systemctl start nginx
Failed to start nginx.service: Unit nginx.service is masked.
kazulog@sv1:~$ sudo systemctl unmask nginx
Removed '/etc/systemd/system/nginx.service'.
kazulog@sv1:~$ sudo systemctl start nginx
kazulog@sv1:~$ systemctl is-active nginx
active
kazulog@sv1:~$ systemctl list-unit-files --type=service --state=enabled --no-pager | head -12
UNIT FILE                              STATE   PRESET
apparmor.service                       enabled enabled
apport.service                         enabled enabled
blk-availability.service               enabled enabled
chrony.service                         enabled enabled
cloud-config.service                   enabled enabled
cloud-final.service                    enabled enabled
cloud-init-local.service               enabled enabled
cloud-init-main.service                enabled enabled
cloud-init-network.service             enabled enabled
console-setup.service                  enabled enabled
cron.service                           enabled enabled