"ERROR: XFS filesystem at /var has ftype=0, cannot use overlay backend" error messages logged by the Docker daemon upon daemon startup

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Issue

During startup of the Docker daemon, an error message of the following format is present in the system logs:

Jun  13 13:55:47 hostname container-storage-setup: ERROR: XFS filesystem  at /var has ftype=0, cannot use overlay backend; consider different  driver or separate volume or OS reprovision

Pre-requisites

Resolution

An xfs formatted filesystem is only supported as backing for the overlay or overlay2 Docker storage drivers if formatted with d_type set to true.

The d_type value of an xfs filesystem can be verified with the xfs_info utility. Example output for this command can be found in the xfs_info man pages. If ftype=1 the filesystem was formatted with d_type true and the filesystem is suitable for use as backing for the overlay or overlay2 storage drivers. If the value is set to 0 the filesystem is not suitable for use with the overlay or overlay2 storage drivers, and would need to be reformated with the flag -n ftype=1.

Per the Docker documentation: "Running on XFS without d_type support now causes Docker to skip the attempt to use the overlay or overlay2 driver. Existing installs will continue to run, but produce an error. This is to allow users to migrate their data. In a future version, this will be a fatal error, which will prevent Docker from starting."

Further reading

Docker documentation on the overlay and overlay2 storage drivers

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