-mount (--one-file-system) like option for rdiff-backup?

Paul Wouters paul@xtdnet.nl
Fri, 28 Jun 2002 03:24:09 +0200 (MET DST)

On Thu, 27 Jun 2002, Ben Escoto wrote:

>     Anyway, there is no --one-file-system option, but there's no
> reason it couldn't be added I suppose.  Why not just use --exclude
> though?  It is too inconvenient when hierarchies have lots of file
> systems in them or the mount points change frequently?

Mostly because then you can keep thinking in "disks". If I add a disk,
I need to explicitely put an entry in the backup scheme. I won't ever
accidently backup the same data numerous times because /usr/local/ is
mounted on /usr is mounted on /
Often, a mounted disk means a different subset of data, eg mail, logs,
webpages, or even a shared directory over multiple machines. It's good
to be able to back those up as seperate data sets.

On my machines, the / filesystem is relatively small, but important 
(for /etc/ for example). Specifying / without 'staying on one filesystem' 
options would backup everything that was mounted on the machine.

Another reason is to just cut down on numerous problems with mounted
filesystems. For instance, I can exclude the most obvious candidates now,
such as /mnt, /tmp, or proc, but I don't know what other features will
be presented in OS'ses at a later stage.
Or users mounting remote NFS directories temporarily (eg some ftp server)

Anyway, a lot of programs have this option, because it has proven to be
very useful. find, locate, rsync, cp, etc etc all have the option. It's
very useful.

>     Also, just to make sure I know what a "file system" is, are two
> files on the same file system if and only if their device numbers are
> the same?  Or is it something else?  For instance, could / and /usr be
> different file systems even if they are both ext2?

with "one filesystem" I meant one instance. eg one mounted directory, or
one physical disk partition. It has nothing to do with the type of
filesystem used (dos,ext2,vfat,nfs).

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