[TUHS] dump(8) compatibility (was: Backup software (was: Irwin 285))

Greg 'groggy' Lehey grog at lemis.com
Mon Feb 15 11:19:14 AEST 2010

On Thursday, 28 January 2010 at 15:27:11 -0500, Brad Spencer wrote:
>    On Thursday, 21 January 2010 at 12:44:49 -0800, Corey Lindsly wrote:
>>> Sure. I know.  Big SATA drives are cheap over here as well, like
>>> 1.5T for 110 EURO or somesuch. I just happen to own a LTO3 and
>>> enough tapes already, so the economics are not the issue. Just need
>>> to have a proper piece of open source backup software that runs on
>>> FreeBSD.
>> And what, precisely, is the problem with using dump?
>> It will span multiple tapes.
>    dump is non-portable.  In general, you can only restore to the same
>    kind of system as you write to.
> Not entirely true...  dump and restore in NetBSD seems to be portable
> among NetBSD systems at least.
> I don't know how far this goes, if it is just NetBSD, or something
> inherent to all 4.4BSD derived systems.

I've just tried to list a FreeBSD 7.2 dump on NetBSD 5.0.1:

  Extract directories from tape
  Mangled directory: reclen less than DIRSIZ (12 < 16)
  (many repetitions)
  Mangled directory: reclen less than DIRSIZ (12 < 16)
  . is not on the tape
  Root directory is not on tape
  abort? [yn] y

Interestingly, FreeBSD restore can understand the NetBSD dump.  But
it's not even backwards compatible between major releases of FreeBSD
even, so this might be the same issue as with FreeBSD.  Either way, I
don't think it's a good idea to count on it for NetBSD in the future.

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