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03.18.04
 By
A.P. Lawrence
Usually upgrades are binary: either they work or they don't. Actually, my experience with SME upgrades has been very good: I've only had a very few where the upgrade process didn't work at all. In those cases, you install new, apply all applicable blades, and then restore from backup. That's annoying, but fairly simple.
But what happens when an upgrade appears to be fine, but a few days later you find that there is actually a serious flaw? That's a bit of a mess: any backup since the upgrade is suspect, but there has been new mail and perhaps other new user files since then that you don't want to lose.
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There is a way out, of course. The first thing to do is to stop more incoming mail: "svc -d /service/smtpfront-qmail" will stop SMTP from accepting new mail. Next, check the queue with "/var/qmail/bin/qmail-qstat" and be sure everything has been delivered before proceeding. You can manually examine any messages in the queue if necessary (something "stuck" might be a message you can easily recreate later if you want to get going now):
[root@mail queue]# /var/qmail/bin/qmail-qstat
messages in queue: 1
messages in queue but not yet preprocessed: 0
[root@mail queue]# cd /var/qmail/queue
[root@mail queue]# find . -type f
./info/5/1713712
./lock/sendmutex
./lock/tcpto
./mess/5/1713712
./remote/5/1713712
[root@mail queue]# more ./mess/5/1713712
While you are waiting for the queue to empty, you need to do backups of the user directories:
cd /home/e-smith/files/users
tar cvf /tmp/myuserfiles.tar .
Put /tmp/myuserfiles.tar on some other machine or transfer it to tape or floppy.
Now do a fresh install of SME. Install all necessary blades and patch updates, followed by the backup (desktop or tape) that was made from the old, pre-upgrade system. The restore procedure is smart enough not to overwrite anything it should not. Finally, bring back /tmp/myuserfiles.tar, and
cd /home/e-smith/files/users
tar xvf /tmp/myuserfiles.tar
That should do it.
I had a call this week from a client who needed a file restored from backup. I had set them up with DVD-RAM and a Supertar a year ago, and had labeled five cartridges with Mon, Tues, etc. I know that (or thought I knew) they followed this rotation for a while, because I had used the previous day's backup to restore files for them earlier this year.
But after ssh-ing in this Thursday and restoring the needed file for them, the woman who needed it called me back and said that she still had incorrect data. I was surprised, and asked if she had indeed put the right cartridge in for me to work from. To my surprise, she replied "I never change it".
"What do you mean?", I asked. "Where's the Tuesday DVD?".
"This is the only one we use", she told me. "You've done this for us before."
Well, OK. Maybe I had, and maybe they never did follow this rotation. Who knows? The data was damaged at 4:00 or 5:00 PM on Wednesday, and of course if she had called me then, I could have restored Tuesdays's data. But she called on Thursday, so the automatic nightly backup had overwritten that. So it's quite possible that I had done this for them before, but I wouldn't be able to do it this time. I explained that to her.
"But I thought this over-wrote the CD every night?", she asked.
That threw me. Not the "CD" part, that's OK. But over-writing is exactly what the backup DOES do, and in fact the printout specifically warns that this happened. There's something about "over-write" that is not being understood there, and we spent a minute or two of me trying to explain that yes, it does over-write and that is why the data she wanted isn't there. I don't know that she completely understood, but she did now understand that the data is gone forever. She wasn't happy, but she understood.
I wondered where the other DVD's were. "Locked in the other office", I was told. I suppose I should have asked why, but at that point she was pretty upset and I didn't want to further her unhappiness. I sent an email to the owner of the company and the resident MIS person explaining what had happened. I hope that they don't blame this woman for the misunderstanding, but it's too important for me not to let them know about.
I feel quite confident that I explained the purpose of the daily labels quite clearly when I installed this stuff, and I also explained that they should call me if there was anything on the backup printout that they didn't understand. Unfortunately, whatever they thought "over-write" meant, they did think they understood what they were doing, so I was completely unaware that they were misusing the system terribly. Nothing we can do about that now, except start doing it right from now on.
This morning I came across this article: Disasters proving to be terminal for many small firms. I can easily believe it.
© Tony Lawrence All rights reserved
About the Author:
A.P. Lawrence provides SCO Unix and Linux consulting services http://www.pcunix.com
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| From the Forum: | | Help!! Windows won't boot! | Earlier today, I was checking email in Outlook 2000, checked a link in a newsletter to open IE5.5x when appeared several 'blue screens'.
When I did the 3 fingered salute, and the system shutdown, on reboot I was told to:
Choose Command Prompt only (on Setup menu)and run SCANREG. ... |
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