>>ufsdump seemed the obvious thing to use but it doesn't seem to like verifying
>>what it's written. I'm writing to DAT tape with it in single user mode; each
>>time I use the verify option it gets so far and then dies with a verify
>>failure. I've tried it from different systems and with different DAT tapes and
>>still get the same problem. Could someone please enlightem me as to why this
>>might occur, and whether this is a bug that has a fix (if so what). What do
>>others do to backup critical data?
Ben Thomson replied:
Quote:> Well, unfortunately we still use 2.2. In 2.2, you cannot verify a backup
> of a mounted file system, because after you do the backup it will almost
> certainly change. You must first unmount the filesystems you are trying
> to dump. This will allow you to verify your backups.
The filesystems being dumped are not mounted; the exceptions are root and /usr
(for some perverse reason, ufsdump exists in /usr rather than in the root file
system so dismounting /usr to back it up loses ufsdump!!!).
In single user mode, which I'm in, only the `necessary' file systems are
mounted (IE root and /usr).
Even if dismounting were to fix the problem, you still have the problem of how
to reliably (I.E. so that the verify option does NOT fail) back up root (and
maybe also /usr).
After talking to sun, I understand there's a product called NETWORKER which
does allow on-line backups reliably; more money of course... they seem to
tacitly admit that ufsdump is a little problematic in this area.
Since backup is such an important part of system management, I find it
mind-numbing that there's no RELIABLE way to do it. To my mind, ufsdump suffers
from the following problems:
1. Backup data is not written with any kind of in-built redundancy checks
so that some classes of tape error can be non-fatal (redundancy data
should allow recovery from simple errors).
2. If a verify error occurs it should be flagged, but the dump should
not be considered fatal (optionally) if the tape is otherwise readable.
This would allow on-line backup (at the system manager's discretion).
One can argue the merits of on-line versus off-line but some sites
have no choice (such as myself!)
3. It appears to offer no protection against the wrong tape being
inserted. Some kind of labelling mechanism, combined with expiry date
protection would be a good move (which is in NETWORKER I'm lead to
If anyone has successfully overcome the problems of reliable backup of file
systems, particularly of root and /usr, I would be more than happy to here how.
Kings College London