Ultrix v2.2 Surprises

[Rob McMahon]

In article <29937 at felix.UUCP> avolio at decuac.dec.com (Frederick M. Avolio) writes
>Wendy et al.  (Wendy, didn'T I meet you at DECUS???)  It is quite safe
>to dump a mounted file system.  Actually, on decuac, we dump file systems
>while the system is multi-user.  What, me scared???  Nahhhh.

We do incremental dumps like this every day, and it has yet to get us
into trouble, although I am conscious that one day the dump is going to
be unusable when we need it and we'll have to go back to the previous
one, so I am still slightly nervous about it.  Just do it at a quiet
time of day, and don't do level 0 dumps this way, it's too important if
they go wrong.

>If you want to wimp out ( :-) ) and run dumps on a quiet system, just shut it
>down to single user, but leave everything mounted.

If you've shut it down to single user, why not umount the filesystem,
for safety.  At the least you should do a 'sync' to make sure the disk
matches memory.

>I guess you might want to
>do an fsck, but would someone who runs dumps on a live system care about
>fsck???

Don't do it!  Running fsck on a mounted filesystem is asking for
disaster.  There are little unconsistencies that can occur while the
filesystem is active, the ones that fsck -p is willing to clean up if
the machine crashes.  If you let fsck patch these on the disk while the
system is active, I shudder at the consequences.

Rob
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Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England