Hello,
> I use aufs as root filesyetem.but I am in trouble. my application use
> contant inode to mark important file, and don't change it. but all inode
> changed when the computer reboot. I don't know how to keep contant inode
> when I reboot machine.
So you want the persistent inode numbers in aufs, right?
Unfortunately the answer is no. Aufs doesn't have such feature.
Actually there is a description in aufs manual.
(from aufs manual)
----------------------------------------
.SH External Inode Number Bitmap, Translation Table and Generation Table (xino)
:::
Aufs uses one external bitmap file and one external inode number
translation table files per an aufs and per a branch
filesystem by default.
:::
The bitmap (and the generation table) is for recycling aufs inode number
and the others
are a table for converting an inode number on a branch to
an aufs inode number.
:::
Once you unmount aufs, the xino files for that aufs are totally gone.
It means that the inode number is not permanent across umount or
shutdown.
:::
After you add branches, the persistence of inode number may not be
guaranteed.
At remount time, cached but unused inodes are discarded.
And the newly appeared inode may have different inode number at the
next access time. The inodes in use have the persistent inode number.
:::
When aufs assigned an inode number to a file, and if you create the
same named file on the upper branch directly, then the next time you
access the file, aufs may assign another inode number to the file even
if you use xino option.
Some applications may treat the file whose inode number has been
changed as totally different file.
:::
----------------------------------------
I know this is a big disadvantage, particularly for exporting aufs via
NFS. In this case, rebooting NFS server will force all NFS clients to
reboot because the inode numbers on NFS server may change.
Many years ago, I had a plan to implement persistent XINO files. Hmm,
now it may be the time to reincur the idea. But don't expect too
much. It will take a few months since I am very busy now.
J. R. Okajima
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