In almost 10 years of my experience with computers, a lot of weird and unbelievable stuff happens.
Windows is starting... aaand it's not
I was told that someone's PC started behaving weirdly and "you certainly need to change that power supply!". So, without thinking too much, I swapped the PSU and it didn't boot properly.
Over 10 restarts, changing SATA ports, changing cables — nothing worked. But let's return back to turning on PC after a PSU swap.
After a POST beep I was greeted with something like this:
__________________________@(//#ard Disk 0 SMART fail
Huh, HDD is not working properly. Well, I skipped this message because PC booted previously. Windows starts showing it's bootscreen aaand hangs. Nothing changes after waiting for five minutes. Just a beautiful Windows 7 logo and that is.
As I said earlier, nothing helped to overcome boot problems. SMART error did not go away either. I took the HDD to other known working computer and it booted first time! That's a relief.
So, I decided that culprit of this PC was the motherboard.
I was given known good motherboard and some spare video cards and memory. One hour later and I start the rebuilt PC. Windows boots, I see the login screen and on this happy note I turn it off.
I closed case door, removed some dust, start it again and...
__________________________@(//#ard Disk 0 SMART fail
Whaa... How?
Symptoms were the same as with previous motherboard, nothing helped. But on one of the reboots I noticed corrputed BIOS boot screen graphics. Huh, the video card is broken? But everything else looks fine on the screen.
I decided that swapping video card won't hurt me and this was the last component that I didn't change.
You already know the answer... It helped... Wimdows booted without a hitch.
What was the problem, you may ask? By the looks of it, somehow, video card I/O was conflicting with HDD I/O. That gave a SMART error and troubles with initializing video driver later.
One byte — one life
The task was simple — delete old version of the antivirus software and install a new one. Everything was even written out in instruction and a script, helping with modifying system files, was given.
I successfully deleted the old version, installed a new one remotely on five machines and got to bed. Only to have calls one hour after work started.
Protected flash drives weren't working. They showed up in system but were not able to coomunicate with authentication server. I immediately blamed the AV and removed it. Didn't help. I started looking through configuration files, but nothing catched my eye.
As a last resort, I called the guys that sent us an updated AV. I've explained the situation and they told me to check one file. And I've checked it before, it looked fine. But as soon as I opened it again, while been on the phone, the culprit showed his trick:
/usr/sbin/named
/usr/sbin/cupsd
/usr/bin/dbus-daemon
/usr/sbin/pcscd/opt/av/bin/avcontrold
Oh. Do you see it? Path to file was appended to the last line. I've opened the install script and found that, yes, it does echo this path to a configuration file. And many of other programs do that in Linux.
But why it failed? Well, *nix has this rule that text file ends in a new line. And this configuration file didn't have it. The last one, who (or a script) edited this file did that in an editor that allows such behavior. Script that AV software used to install itself was correct.
I decided to test, can I make a file without a new line. It was very easy. mcedit allows that behavior, but nano does not. You can delete the last line and nano will add it for you.
One byte caused chaos for two hours.
I will not work on communist's computer!
Another day, another printer decided to screw it's owner. It was a simple EPSON inkjet printer. It had worked previously, but suddenly stopped printing.
Drivers were not only not printing, but gave an unknown error when a new print task started. Also, at startup monitor application thrown an error of file missing. You guessed it — it was there, in it's folder.
Many reinstalls after, cleaning drivers manually from print server — nothing helped.
But then, at another attempt at installing newer version of a driver I looked at a first window that asked what language I want to install. By default, it was Russian, because system language was it too. On a whim, I switched it to English and proceeded with installation.
And suddenly a status monitor window appears! Oh yeah! I've quickly opened printer settings and sent a test page. Squeaking noises came from over my head, where printer sat. I was so happy and baffled all together.