Masking a service prevents the service from being started manually or automatically, which is a stronger version of disable .Masking disable all symlinks of the specified unit file are removed.
Example :
root@opensource:~# sudo service docker restart Failed to restart docker.service: Unit docker.service is masked. root@opensource:~# docker –version Docker version 19.03.5, build 78d1802
In case of Sysctl Masking shows the same output :
root@opensource:~# sudo systemctl enable docker Synchronizing state of docker.service with SysV service script with /lib/systemd/systemd-sysv-install. Executing: /lib/systemd/systemd-sysv-install enable docker Failed to enable unit: Unit file /etc/systemd/system/docker.service is masked.
We can to unmask the docker service like below
root@opensource:~# systemctl unmask docker.service Removed /etc/systemd/system/docker.service. root@opensource:~# systemctl unmask docker.socket root@opensource:~# systemctl start docker.service
Now docker and docker service will be working as usual
root@opensource:~$ systemctl list-unit-files | grep docker docker.service enabled docker.socket enabled
root@opensource:~$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES