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SubjectRe: Amanda VFAT Incremental Backups Broken in linux-2.2.1[12]
On Sat, 4 Sep 1999, Khimenko Victor wrote:

> In <9e86d1b443edfd13@home-box.demon.co.uk> Robert de Bath (rd103983@home-box.demon.co.uk) wrote:
> > DONT BACKUP VFAT INCREMENTALLY
------------------------------
>
> > There is only one date on a file on a VFAT partition and as every command
> > down to the DOS copy command preserves that date you cannot see what's
> > been changed.
>
> This is WRONG. VFAT (but NOT plain old MS-DOS FAT !!!) has three times as it
> should be: Modification time (this is old good MS-DOS "modification time";
> preserved by copy), Creation time (not preserved by copy) and "Last access
> time" (date actual -- time is not stored; not preserved by copy). At least it
> is on disk -- I'm not sure if Linux's VFAT driver supports them...
>
> > Hopefully the ctime is being set to now (or now-1); this is the
> > _right_ thing to do.
>
> Why so ? Why not use existing three times ? Even if "Last access time" is not
> time but date...

Oh hum, I'd forgotten that VFAT had those times, but it's still not sufficient.

For unix:

mtime: The time the file was last modified.
atime: The time the file was last accessed.
ctime: The last time _any_ change was made to the file or inode.

All times are to the second.

For VFAT
mtime: The time the file was last modified (2 second resolution)
atime: The time the file was last accessed (86400 second resolution)
ctime: The time the file was _created_ (1ms resolution)

I suppose the unix ctime could be the max of these times.
I don't think I'd trust it enough to backup incrementally even tho it'd
pick up the commonest problem of a single mtime; unpacked zip files.

--
Rob. (Robert de Bath <http://poboxes.com/rdebath>)
<rdebath @ poboxes.com> <http://www.cix.co.uk/~mayday>



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