dump | restore fails: unknown tape header type 1853384566

[Mikhail T.]

Greg Black написав(ла):
> On 2009-03-24, Mikhail T. wrote:
>   
>> That's true. I just wanted to point out, that someone running dump only 
>> (to make backups) is not going to know, whether his dumps are usable 
>> (for whichever of the two reasons), until he needs them...
>>     
>
> Such a person is not making backups and deserves what he gets.
>   
But he *is* making backups -- kindly re-read my paragraph above... He 
just is not routinely using them and thus does not know, that they 
aren't usable... It is not unreasonable to expect the two utilities to 
"just work", so I wouldn't be blaming such a person for not testing 
restore.

That such a scenario is possible, despite the user making diligent 
regular backups, is a very bad sign...
> I haven't got anything to say about dump/restore because I haven't
> bothered with them for years.  I do know that dumps from mounted file
> systems will often appear to work, but will fail when it matters.  This
> is not a bug and is expected behaviour to which the solution is obvious.
>   
FS being mounted read-only should not be a problem. And even read-write 
mounted filesystems will be Ok, although possibly inconsistent (a file 
modified during backup may get to into dump "as of" any point). But an 
idle FS is Ok to dump. Generally, when dumping read-write mounted 
filesystems, one is supposed to use snapshots, but that is very buggy on 
its own (leading to kernel crashes), so it is safer to rely on the FS 
being "idle", if it can not be forced into read-only for some other reason.

    -mi