[resending...had a bounce]
>From: Nathan Scott <nathans@xxxxxxx>
>On Wed, Nov 10, 2004 at 05:52:57PM +0100, wojtek@xxxxxxxxxxxx wrote:
>> Is it true that every file and directory has its own UUID? And if so: is it
>> accessible to user programs? Can it be made accessible?
>Hmm, if you mean UUID's like those described in libuuid(3), then
>no - each filesystem has a UUID, but not each file. Each file has
>an inode number of course... and XFS does provide mechanisms to get
>to files and directories via inode number.
Each file does have a unique identifer, called a handle. The handle is a
tuple containing (filesystem id, inode number, inode generation number). So
while it's not a uuid, it is, however, unique.
>> We want to develop a system that would store part of its data in the
>> filesystem, and part in the database. It would be very convenient to have
>> an unique and stable (surviving backup - restore, dump) filesystem object
>> identifiers, and also uid -> path, or open by uid functionality.
The handle won't be persistent across a dump/restore (as you can probably
guess, now that you know its contents).
You can put a unique identifier in an extended attribute and let xfsdump and
xfsrestore carry the extended attributes around for you.