[rescue] Tape Backup

[Stephen D. B. Wolthusen]

Hi,

On 18-Sep-2002 Geoffrey S. Mendelson wrote:

> No, I don't know of any because AFIK all CD's are written at once, so
> you have to have built an image of the CD before you do it.

Well, not quite. Even `regular' CDs can be multisession, and programs like
cdrecord support this. The individual sessions are created using regular
mkisofs. Theoretically there's an alternative with UDF (packet writing) that is
less wasteful than multisession CDs (which waste approx. 20MB per session in
overhead), but while e.g. Solaris has been able to read CDs and DVDs with UDF
since S8, I'm not aware of any packet writing app or device driver under any
Unix flavor.

> Note that ISO9660 file systems have some limitations and if you have
> pipes, really long file names, need permissions copied, etc, make
> a tar file instead. You'll still have to make an image before you write
> it.

mkisofs supports hybrid Rock Ridge / Joliet CDs, so you can create CDs that are
readable on most reasonably recent Unix derivatives (i.e. with Rock Ridge
support) as well as M$ products. Tar balls are useful, though, if you have to
deal with exotic/elderly systems, want to retain permissions across the backup
(although again, that *can* also be done with mkisofs), and particularly when
you have deep directory hierarchies, which are not supported by ISO 9660.

And if your system has enough oomph CPU and I/O-wise (especially for fragmented
and/or NFS data) you can run mkisofs/cdrecord (burncd, whatever) as a pipe.
YMMV.

-- 

        later,
        Stephen

Stephen Wolthusen (stephen at wolthusen.com)