On Wed, 26 Mar 2003, Tzafrir Cohen wrote:

> >
> > The idea is sound. Note:
> >
> > Be sure you replicate the _entire_ system
> > dd  may be faster than tar | tar. Depends on how much data.
>
> Doing either of those things on a running system exposes you to a chance
> of copying an inconsistant filesystem. I believe that the tar method is
> a bit safer.

Neither is sound if source filesystems are mounted rw. However, he did
say "boot from CD" from which I expect he knows that.


>
> BTW: you assume that the whole system is on one partition (/), right?
I didn't. That is why Isaid, "Be sure you replicate the _entire_
system."
>
> >
> > Some S/390 storage systems can have their own means of replicating
> > volumes. That is likely to be faster.
>
> Even if the system allows you to copy a snapshot of a partition (I think
> LVM is supposed to allow this, I'm not sure whether or not S/390 has
> something equivalent) the filesystem may be in an inconsistant state
> at the time of the snapshot. It will certainly be "not safely
> unmounted". This applies for the dd method above.

LVM allows consistent backups, but I was referring to ha hardware
facility in the drive subsystem itself. I recall someone from Stotech
describing theirs, and I think IBM's Noah's Ark can do it.


>
> >
> > You might prefer to run rpm thus:
> > rpm --root /mnt ...
> >
> > Probably doesn't matter in this case, but this approach doesn't require
> > rpm to be installed on the target.
>
> Doesn't it?
>
> I recall reading somewhere that it uses the binary /bin/rpm of the
> chrooted system for some stuff . I don't recall exactly where, maybe a
> certain bug report. Maybe you should test this.

It's how I've initialised an empty rpm database in an empty filesystem.

I've also used it, years ago, to fix a RHL 3.0.3 system when RH upgraded
RPM twice (or more) making it impossible to go from original to current
without laying hands on all the intermediate version.

On that occasion, I exposed the entire filesystem via NFS and used
another system to fix it.


--


Cheers
John.

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