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Unmask a Masked Service in Systemd

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:

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

Looking at the nfs-common service:

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$ 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:

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$ 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:

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

Then reloading the daemon:

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$ sudo systemctl daemon-reload

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

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$ 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:

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$ 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:

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$ 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

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