Re: tar, backup, growisofs, file names
> i guess i can give up the "filesystem and filenames" bit, if i
> figure out how to access the later incremental backups.
> would that work with growisofs just as with a sequential streamer device?
The way tar ("tape archive") works on tapes is to dump a stream of
blocks at the beginning of the tape. Next time, it's your responsibility
to wind the tape to the end of the first recording, then you dump
another stream of blocks starting at that point on the tape, and so on.
You can easily have the same effect with DVD+RW and kernel-patch:
tar ... | dd obs=16k seek=0 of=/dev/sr0
and dd outputs something like "1234+1 blocks written". Your first
recording is now 1235 blocks long. Next time, you do:
tar ... | dd obs=16k seek=1235 of=/dev/sr0
and so on. Difference: on tape, you can wind to end of next recording,
on DVD, you either note down the starting block numbers, or record a
null block between recordings *and* make sure you never have a null
block inside your tar output (easy if you compress it). You can then
"wind" by searching for a null block.
Reading is
dd ibs=16k skip=1235 if=/dev/dvdrom | tar ...
The 2 shortfalls of random-access DVD+RW writing, unreliable
granularity when writing <16k and lack of random-write filesystem
performance, do not apply in this case as the output block size of dd
is 16k, and you're only burning sequentially after one seek without
using a filesystem at all.
Remaining question: can each of these tar files be burnt into its own
session (or whatever that's called on DVD)? In that case, it should be
possible to use any DVD+-R(W) and growisofs (making sure not ti
fixate), instead of the kernel patch.
Volker
--
Volker Kuhlmann is possibly list0570 with the domain in header
http://volker.dnsalias.net/ Please do not CC list postings to me.
Reply to: