Re: [rdiff-backup-users] Finding/designing a tar replacement

[Ben Escoto]

On 24 Sep 2003 08:46:38 +0100 Kevin Spicer <address@hidden> wrote:
> Have you considered using .iso (iso9660, ie CD rom format) files as the
> container?  You can mount them under Linux as a file-system without
> having to burn them to CD, and they are ideal for people who ultimately
> want to store their backups on CD.  I suppose there might be issues with
> having to split large files, and issues with what metadata the
> file-system supports (but check the available extensions, there seems to
> be a lot of options).  Certainly as a container format it has the
> benefits of being a file-system so you can quickly access files anywhere
> in it, you can store arbitrary extra data by simply creating an extra
> top level hierarchy.

Neat, that's a good idea.  The strategy of using volumes as file
systems should be an important consideration.  I didn't even know that
Linux could mount an iso image.  (How can I try this?)  What other
files can be mounted?  The ReiserFS people want people to be able to
mount files like /etc/passwd, but presumably that won't be mainstream
for a while.  But if it does, maybe tar files and everything else will
be mountable, so mounting will no longer be a consideration.

About extensions, the only iso9660 extensions I'm aware of are Joliet
and Rock Ridge.  Neither will get you extended attributes and what
not, but at least there existence suggests that iso9660 can be
extended in a backwards compatible fashion.

Apparently the ISO standards are not public domain, but presumably
enough information on iso9660 is out there somewhere.  Looking at a
vague description of the format, it does seem that such a volume can
be written before the lengths of the files are known, because the path
table can occur after file data.  Can anyone confirm this?  Can CD
burners burn in one pass?

Also apparently the file size inside iso9660 is limited to 2GB.
Finally I don't see any way of encrypting or compressing the entries
in an iso9660 volume and still preserving the easy mounting
ability.


-- 
Ben Escoto

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