How to Troubleshoot a Frozen or Crashed Computer

You come in one morning or come back from lunch to find an unresponsive workstation / computer, what can you do?

Perhaps the system is simply turned off! A power interruption could have caused this. If your computer is connected to a UPS (Uninterruptible Power Supply) and it was configured properly, then your system was no doubt shutdown properly as well. So in this case power up the system!

If you’re unsure whether the system is on or not, then you need to be observant. Is the system making any noises? Do you see lights / LED(s) blinking? Do you have video?

Most computer chassis have a power LED and also another LED showing disk activity. You should find these at the front of the chassis, sometimes inside the front panel. Are those LEDs on or blinking? You can also get some clues by looking at the back of the chassis - there you should find the PSU (Power Supply Unit) fan churning (or not), one or more chassis fans churning (or not). If your computer is networked, then follow the network cable to the chassis and you should also find LEDs blinking there as well.

Note that depending on the chassis, you may find fans at the top, on the side, at the front … learn to familiarize yourself with your computer to detect signs of trouble! Some computer chassis are very silent and hardly make any noise, so you need to get close - use a flash light to detect fan movement and/or put your hand close to the fan.

Sometimes the answer is obvious as you see a text console with plenty of seemingly cryptic words confirming that the computer kernel has crashed or panicked, something like this: or like this

If this is the case, then your only option is to reset the system by pressing the reset button. If you don’t know where this button is located, it’s usually not too far from the power button, yet smaller. Using the tip of your smallest finger should do it - don’t use anything sharp.

If you have video, can you get a text console by pressing Ctrl-Alt-F1 ? There are usually 8 consoles on a linux system, you can access them by pressing Ctrl-Alt-F1 through Ctrl-Alt-F8, while the graphics console is usually on Ctrl-Alt-F7 or Ctrl-Alt-F8. If your video is jammed, you could try restarting it by pressing Ctrl-Alt-Backspace.

If you have no video, pay attention to the keyboard - are the keyboard LED(s) flashing? If so, this would indicate a kernel panic. Also, are you able to use the CapsLock and/or NumLock keys? When you press them, do their respective keyboard LEDs come on and off? If that works, then the kernel is still active. The problem could be limited to video - check the video cabling, as something could have come loose - make sure everything is tightly attached and screwed in.

Can you ping the system ? You could do this from another computer:

$ ping 
PING ( 56(84) bytes of data. 
64 bytes from ( icmp_req=1 ttl=64 time=0.208 ms 
64 bytes from ( icmp_req=2 ttl=64 time=0.255 ms 
64 bytes from ( icmp_req=3 ttl=64 time=0.279 ms 
64 bytes from ( icmp_req=4 ttl=64 time=0.309 ms 
64 bytes from ( icmp_req=5 ttl=64 time=0.242 ms 

--- ping statistics --- 
5 packets transmitted, 5 received, 0% packet loss, time 3997ms 
rtt min/avg/max/mdev = 0.208/0.258/0.309/0.038 ms`

Can you ssh into the system?

$ ssh

Replace login with the name of your workstation / system.

Computer trouble comes in many forms … bad hardware, nasty software … but now that you know some basic stuff, you can solve basic issues - which are quite common!

In any event, you should contact your system administrator to explain your troubles, while he or she will no doubt already be aware that something is amiss, he or she may need your input, especially if nasty software is involved.

If you need help, contact us at bicadmin AT