From cbb44f0935974bba997f8db0458fac5739ae0009 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 7 Jul 2023 11:26:29 +0300 Subject: ovl: auto generate uuid for new overlay filesystems Add a new mount option uuid=auto, which is the default. If a persistent UUID xattr is found it is used. Otherwise, an existing ovelrayfs with copied up subdirs in upper dir that was never mounted with uuid=on retains the null UUID. A new overlayfs with no copied up subdirs, generates the persistent UUID on first mount. Signed-off-by: Amir Goldstein --- Documentation/filesystems/overlayfs.rst | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'Documentation/filesystems') diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index 8275ed735f77..35853906accb 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -664,7 +664,7 @@ UUID and fsid The UUID of overlayfs instance itself and the fsid reported by statfs(2) are controlled by the "uuid" mount option, which supports these values: -- "null": (default) +- "null": UUID of overlayfs is null. fsid is taken from upper most filesystem. - "off": UUID of overlayfs is null. fsid is taken from upper most filesystem. @@ -674,6 +674,12 @@ controlled by the "uuid" mount option, which supports these values: UUID is stored in xattr "trusted.overlay.uuid", making overlayfs fsid unique and persistent. This option requires an overlayfs with upper filesystem that supports xattrs. +- "auto": (default) + UUID is taken from xattr "trusted.overlay.uuid" if it exists. + Upgrade to "uuid=on" on first time mount of new overlay filesystem that + meets the prerequites. + Downgrade to "uuid=null" for existing overlay filesystems that were never + mounted with "uuid=on". Volatile mount -- cgit v1.2.3