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|Acronis True Image||Rush/absence of testing||Creative uses of rm||Abuse of privileges||LVM and disk related mishaps||Working on the wrong computer|
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If you try to distill the essence of horror stories, most of them are about inadequate backups. Everyone who has worked as system administrator in a large corporation for substantial period of time can tell that as a general observation, large organizations/corporations tend to opt for incredibly expensive, incredibly complex, incredibly overblown backup "solutions" sold to them by vendors rather than using the stock, well-tested, reliable tools that they already have. (e.g., Data Protector, Tivoli backup, or other expensive closed-source/proprietary/non-portable/slow/bulky software.
Home users have their own set of problems: According to a recent Carnegie-Mellon University report, hard drive failures affect up to 13 percent of all personal computer users each year. And yet surveys show almost half of users do not back up their data. Of cause now SSD are not that expensive, but they fail too, although they are more resistant to falling from the desk on the floor.
Having a good recent backup that can be restored is the key feature that distinguishes mere nuisance from full blown disaster. note that phzse " that can be resotred". This point is very difficult to understand by novice enterprise administrators. often the "missing backup" situation arise when backup is available but can't be used for restoration or restores only a part of filesystem, or is not current. There are some rules that help both prevent such situation and recover from it
Rephrasing Bernard Show we can say "Experience keeps the most expensive school, but most sysadmins are unable to learn anywhere else". Please remember that in enterprise environment you will almost never be rewarded for innovations and contributions but in many cases you will be severely punished for blunders. In other words typical enterprise IT is a risk averse environment and you better understand that sooner rather then later...
If you try to distill the essence of horror stories most of them are about inadequate backups. Having a good recent backup is the key feature that distinguishes mere nuisance from full blown disaster.
You should not be passing in accepting you fate. There should be couscous efforts to locate and test backup before engaging in some potentially dangerous manipulations with the OS.
|Test your backups to make sure they are readable before starting any
potentially dangerous manipulations with the OS.
Handle the format program (and anything else that writes directly to disk devices) like nitroglycerine.
If you've never done sysadmin work before, take a formal vendor training class even if this means paying your own money.
Testing your backups periodically should be a habit and it is better to be integrated into your monitoring system. Attempt at least to browse the backup and see if data are intact is a must. comparing it with the server state is even better. In any case that should be done. Skipping this means negligence on the part of system administrator.
Please remember that backup is the last change for you to restore the system if something went terribly wrong. That means that before any dangerous steps you need to locate and check the existence of backup.
In eneterprise environment making a private backup is also a good idea to that you have two or more recent copies of your OS and some user and data directories. It does not need to be complete. FIT falsh drives limit the total size to 128GB, but they are almost invisible after you insert them into USB port on the server and they provide improtant and cheap insurance for your OS, baseline and critical user and data files.
The felling of desperation one is experiencing after getting into this classic horror story are well reflected in the following parody on Yesterday
All those backups seemed a waste of pay.
Now my database has gone away.
Oh I believe in yesterday.
There's not half the files there used to be,
And there's a milestone hanging over me
The system crashed so suddenly.
I pushed something wrong
What it was I could not say.
Now all my data's gone
and I long for yesterday-ay-ay-ay.
The need for back-ups seemed so far away.
I knew my data was all here to stay,
Now I believe in yesterday.
If you are not careful you can wipe out your C disk performing a restore of the Windows C partition image to a USB drive, as selection of bootable recovery image somehow redirects recovery to disk C. The warning sign is when Acronis True Image wants to reboot computer to proceed.
If you are brave enough to go past this point, then despite the fact that you explicitly made your target different from bootable drive you need to face unpleasant consequences -- your C partition is now gone.
You can imagine your surprise with the results. I once did that. Thanks God there was no critical data on this wiped C drive. I already migrate it to a new PC. My first reaction was to throw this garbage program where it belongs. But the problem is that other similar programs are not much better and now I am trained not to trust Acronis and probably can do better in future. Another factor is that if you don't use Acronis True Image often you forget about it capabilities (in this case the write decision would be to use cloning of the disk operating, not restoration from the image but the problem was that the disk and image were slightly different and I want the content of the image not the content of the disk.
Still right way would be to do first clone of the disk and then perform restoration of the image to this drive. As I don't use complex operations with Acronis often, I forgot about that and was punished. And believe me you jaw really drops in such cases when you see the results...
Another time, our AIX/370 cluster managed to trash the /etc/passwd file. All 4 machines in the cluster lost their copies within milliseconds. In the next few minutes, I discovered that (a) the nightly script that stashed an archive copy hadn't run the night before and (b) that our backups were pure zorkumblattum as well. (The joys of running very beta-test software).
I finally got saved when I realized the cluster had *5* machines in it - a lone PS/2 had crashed the night before, and failed to reboot. So it had a propogated copy of /etc/passwd as of the previous night.
Go to that PS/2, unplug it's Ethernet.. reboot it. Copy /etc/passwd to floppy, carry to a working (?) PS/2 in the cluster, tar it off, let it propogate to other cluster sites. Go back, hook up the
crashed PS/2s ethernet.. All done.
Only time in my career that having beta-test software crash a machine saved me from bugs in beta-test software. ;)
Once I was in the position of upgrading a Gould PN/9080. I was a good sysadmin, took a backup before I started, since the README said that they had changed the I-node format slightly. I do the upgrade, and it goes with unprecidented (for Gould) smoothness. mkfs all the user partitions, start restoring files. Blam.
I/O error on the tape. All 12 tapes. Both Sets of backups.
However, 'dd' could read the tape just fine.
36 straight hours later, I finally track it down to a bad chip on the tape controller board - the chip was involved in the buffer/convert from a 32-bit backplane to a 8-bit I/O cable. Every 4 bytes, the 5th bit would reverse sense. 20 mins later, I had a program written, and 'dd 3 my_twiddle 3 restore -f -' running.
Moral: Always *verify* the backups - the tape drive didn't report a write error, because what it *received* and what went on the tape were the same....
I'm sure I have other sagas, but those are some of the more memorable ones I've had...
Computer Systems Engineer
From: rca@Ingres.COM (Bob Arnold)
Organization: Ask Computer Systems Inc., Ingres Division, Alameda CA 94501
Many moons ago, in my first sysadmin job, learning via "on-the-job training", I was in charge of a UNIX box who's user disk developed a bad block. (Maybe you can see it already ...)
The "format" man page seemed to indicate that it could repair bad blocks. (Can you see it now?) I read the man page very carefully. Nowhere did it indicate any kind of destructive behavior.
I was brave and bold, not to mention boneheaded, and formatted the user disk.
The good news:
1) The bad block was gone.
2) I was about to learn a lot real fast :-)
The bad news:
1) The user data was gone too.
2) The users weren't happy, to say the least.
Having recently made a full backup of the disk, I knew I was in for a miserable all day restore. Why all day? It took 8 hours to dump that disk to 40 floppies. And I had incrementals (levels 1, 2, 3, 4, and 5, which were another sign of my novice state) to layer on top of the full.
Only it got worse. The floppy drive had intermittent problems reading some of the floppies. So I had to go back and retry to get the files which were missed on the first attempt.
This was also a port of Version 7 UNIX (like I said, this was many moons ago). It had a program called "restor", primordial ancestor of BSD's "restore". If you used the "x" option to extract selected files (the ones missed on earlier attempts), "restor" would use the *inode number* as the name of the extracted files. You had to move the extracted files to their correct locations yourself (the man page said to write a shellscript to do this :-(). I didn't know much about shell scripts at the time, but I learned a lot more that week.
Yes, it took me a full week, including the weekend, maybe 120 hours or more, to get what I could (probably 95% of the data) off the backups.
And there were a few ownership and permissions problems to be cleaned up after that.
Once burned twice shy. This is the only truly catastrophic mistake I've ever made as a sysadmin, I'm glad to be able to say.
I kept a copy of my memo to the users after I had done what I could. Reading it over now is sobering indeed. I also kept my extensive notes on the restore process - thank goodness I've never had to use them since.
1) The "man" pages don't tell you everything you need to know.
2) Don't do backups to floppies.
3) Test your backups to make sure they are readable.
4) Handle the format program (and anything else that writes directly to disk devices) like nitroglycerine.
5) Strenuously avoid systems with inadequate backup and restore programs wherever possible (thank goodness for "restore" with an "e"!).
6) If you've never done sysadmin work before, take a formal training class.
Well, I haven't thought about that one in a while! I can laugh about it now ....
From: rca@Ingres.COM (Bob Arnold)
Organization: Ask Computer Systems Inc., Ingres Division, Alameda CA 94501
In article <1992Oct12.233524.13463@pony.Ingres.COM> I wrote:
>I was brave and bold, not to mention boneheaded, and formatted the user disk.
> U rest of story deleted ... Bob ~
> 1) The "man" pages don't tell you everything you need to know.
> 2) Don't do backups to floppies.
> 3) Test your backups to make sure they are readable.
> 4) Handle the format program (and anything else that writes directly
> to disk devices) like nitroglycerine.
> 5) Strenuously avoid systems with inadequate backup and restore
> programs wherever possible (thank goodness for "restore" with
> an "e"!).
> 6) If you've never done sysadmin work before, take a formal
> training class.
Just thought of a few more related morals (managers pay attention now):
7) You get what you pay for.
8) There's no substitute for experience.
9) It's a lot less painful to learn from someone else's experience than your own (that's what this thread is about, I guess :-) )
Part of the story I should tell here. My employer had been looking for a way to cut costs. I was 15% cheaper than their previous sysadmin so they let him go and hired me. It wasn't as nasty as it sounds, since they kept him on as a consultant at 4 hours a week and he ended up with a better job too (so did I). Everyone benefited in the end. I leaned heavily on his consulting, which was great. He was older and wiser, and probably had his own horror stories to tell. After this one, so did I!
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