On Tue, Nov 26, 2024 at 04:35:13PM +0100, Roger Price wrote:
My understanding is that a Linux file system is a hierachical structure starting with the root directory (/) which organises the directories and files. The files are stored on various devices which have identities such as /dev/sdxn, UUID or LABEL. These identities are for the devices, not parts of the file system.
Your understanding is wrong: the UUIDs you are talking about are a feature of the filesystem--that's why they appear in lsblk -f (filesystem) output. You can find the same UUID in filesystem-specific tools such as dumpe2fs; lsblk has logic to extract a UUID from each filesystem that it knows how to parse and which contains a UUID. There are other UUIDs associated with some storage devices, partitions, and all sorts of other things on a modern system, but they are not the filesystem UUID and are not what is displayed in lsblk -f. (lsblk -f does include some UUIDs which aren't in filesystems, but which are in some other on-disk structure logically similar to a filesystem; an example is LVM physical volumes [also visible via pvs -v].)
