Unmask a Masked Service in Systemd

Systemd is a powerful system and service manager for Linux operating systems. Sometimes, services can become masked, preventing them from starting or running properly. In this tutorial, we will walk you through the steps to unmask a masked service in systemd on Ubuntu Linux.

Checking the Status of the Masked Service

I was busy setting up a docker-volume-netshare plugin to use NFS Volumes for Docker, which relies on the nfs-utils/nfs-common package, and when trying to start the service, I found that the nfs-common service is masked:

$ sudo systemctl start docker-volume-netshare.service
Failed to start docker-volume-netshare.service: Unit nfs-common.service is masked.

Unmasking the Service

Looking at the nfs-common service:

$ sudo systemctl is-enabled nfs-common
masked

$ sudo systemctl enable nfs-common
Synchronizing state of nfs-common.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable nfs-common
Failed to enable unit: Unit file /lib/systemd/system/nfs-common.service is masked.

It appears that the unit file has a symbolic link to /dev/null:

$ file /lib/systemd/system/nfs-common.service
/lib/systemd/system/nfs-common.service: symbolic link to /dev/null

I was able to unmask the service by removing the file:

$ sudo rm /lib/systemd/system/nfs-common.service

Reloading the Systemd Daemon

Then reloading the daemon:

$ sudo systemctl daemon-reload

Starting and Enabling the Service

As we can see the nfs-common service is not running:

$ sudo systemctl status nfs-common
● nfs-common.service - LSB: NFS support files common to client and server
   Loaded: loaded (/etc/init.d/nfs-common; generated; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:systemd-sysv-generator(8)

Let's go ahead and start the service:

$ sudo systemctl start nfs-common
$ sudo systemctl status nfs-common
● nfs-common.service - LSB: NFS support files common to client and server
   Loaded: loaded (/etc/init.d/nfs-common; generated; vendor preset: enabled)
   Active: active (running) since Sat 2017-12-09 08:59:47 SAST; 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 7382 ExecStart=/etc/init.d/nfs-common start (code=exited, status=0/SUCCESS)
      CPU: 162ms
   CGroup: /system.slice/nfs-common.service
           └─7403 /usr/sbin/rpc.idmapd

Now we can see the serive is unmasked and started, also remember to enable to service on boot:

$ sudo systemctl enable nfs-common
nfs-common.service is not a native service, redirecting to systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable nfs-common

$ sudo systemctl is-enabled nfs-common
enabled

Conclusion

By following these steps, you can easily unmask a masked service in systemd on Ubuntu Linux. This ensures your services run as expected, improving your system's reliability.

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