LVM volume groups with a name of 'root' will have naming collisions when systemd-udev-root-symlink service is active.

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Environment

SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)
SUSE Linux Enterprise Server 12 Service Pack 2 (SLES 12 SP2)

SUSE Linux Enterprise Server 12 Service Pack 3 (SLES 12 SP3)

Situation

When a LVM VG named 'root' which contains a logical volume needed for boot exists, and the systemd-udev-root-symlink service is active, the boot log will show messages similar to this :

rename '/dev/root.tmp-b254:0' '/dev/root' failed appears when the system start on a LVM configured host.

Resolution

There are two possible solutions to this issue:

1. Since LVM VG's create /dev entries with the same name, do not choose VG names which may be used by other devices or services.

2. The /dev/root link provided by the systemd-udev-root-symlink service is currently deprecated and will be removed from future systemd versions.

The /dev/root symlink created is not currently used by any system components. As such, if a customer environment also does not make use of the /dev/root symlink, the systemd-udev-root-symlink service may be masked with the command:

systemctl mask systemd-udev-root-symlink.service

Cause

The LVM vgcreate command verifies that there is currently no '/dev' entry which has the name of the volume group being created. However, this does not stop a service which is started later, or a device from being added at a later time, which may be using the same name for a '/dev' entry.

The system administrator should exercise caution in choosing VG names to ensure such collisions do not occur.

Additional Information

When a LVM VG named 'root' contains a logical volume needed for boot, and the systemd-udev-root-symlink service is active, when the system starts up the boot log will show messages similar to :

11:25:47 LINUX123 systemd[1]: Started Rule generator for /dev/root symlink.
11:25:48 LINUX123 systemd-udevd[1901]: rename '/dev/root.tmp-b254:0' '/dev/root' failed: Is a directory

Disclaimer

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