What to do when system hangs?

[knite75]

In Windows, I can press Ctrl-Alt-Del.

What's on Linux side?

Is there a "task manager" that I can select the programs that are "not running" and "end process?"

[nargy]

on a console: press Ctrl+Alt+Del
in the graphical environment: press Ctrl+Alt+Backspace
if it doesn't reboot or unfreeze your computer, try connecting from another computer (telnet, ssh) and kill hanging process by hand. Use commands: top (lists runing processed), ps axf (list all processes), killall <processname> (request for a process to terminate), killall -9 <procname> (force a process to terminate).
If none of these worked, try the reset button

[crossfire]

Originally Posted by knite75

In Windows, I can press Ctrl-Alt-Del.

What's on Linux side?

Is there a "task manager" that I can select the programs that are "not running" and "end process?"

Well If you open a terminal you can give

ps -aux

to see what tasks (process) are running...

And you can kill the process that you fells locked.

kill -9 process_number

Be carefull doing this ok...

If your graphical system seems to be locked do CTRL-ALT-BACKSPACE (will enter in text mode) and do these commands(above) in text mode. To return give telinit 5.

[addarich]

ctrl-alt-backspace, will bring the x11 down, togheter will all you programs for that x section
on a terminal you can run top, see what program you want to kill and type
kill [jobid]
ctrl-alt-delete should reboot your computer if it is properly set up

[knite75]

Thank you for all the quick replies.

Sorry, I probably didn't explain the problem clearly. However, when my computer hung, I was able to do anything, include openning up the terminal. The mouse and everything else just froze, until my patience ran out and held down the power button and reboot.

However, when my computer hung, I was not able to do anything, include openning up the terminal. The mouse and everything else just froze, until my patience ran out and held down the power button and reboot.

This has happened to me as well, but holding the power button has no effect so I have to unplug the power cord from the case. I'd be very interested in hearing a fix.

[jayemef]

You should be able to switch to a virtual terminal though. CTRL+ALT+Fx will do it, where x is generally a number between 1 and 6. For example, CTRL+ALT+F1, or CTRL+ALT+F3. You should get a black screen with a command prompt. From there, log in as you normally would. Then you should be able to use the command top to see what processes are running. To go back, you can log out of that terminal with exit, then to get back to the graphical environment (5), press ALT+Fx, where x is usually between 7 and 8. (It's 7 on my personal machine, and 8 on a server I run. Not entirely sure why its different on different machines. If anyone knows, I'd be interested.)

As far as CTRL+ALT+BACKSPACE, this will restart X for you. The consequence here is that all the applications you had running will close, whereas with the first method, you can close each one specifically.

**Note: uppercase X refers to the X-Window-System, where lowercase x is a variable.

[WidreMann]

Originally Posted by jayemef

You should be able to switch to another run level though. CTRL+ALT+Fx will do it. For example, CTRL+ALT+F1, or CTRL+ALT+F3. You should get a black screen with a command prompt. From there, log in as you normally would. Then you should be able to use the command top to see what processes are running. To go back, you can log out of that run level with exit, then to get back to the graphical run level (5), press ALT+Fx, where x is usually between 6 and 8. It's 7 on my personal machine, and 8 on a server I run. Not entirely sure why its different on different machines. If anyone knows, I'd be interested.

As far as CTRL+ALT+BACKSPACE, this will restart x for you. The consequence here is that all the applications you had running will close, whereas with the first method, you can close each one specifically.

Those aren't runlevels, but rather the virtual consoles. By default, the first six virtual consoles are for text-only login (CTRL-ALT+Fx where x is 1 to 6) and the 7th virtual console is used for your X session. I believe that X will use the first free virtual console, so if something grabs virtual console 7 before X does, then X will be on virtual console 8 or later. You can in fact have multiple X sessions, each on a different virtual console. When I'm at home with my laptop, I will sometimes start up another X session connected to my other Linux machine allowing me to have two desktops at once, one for each machine. The 2nd X session will usually be on virtual console 8 unless I've already put something there.

You can start a program on a virtual console using the openvt command, which lets you specify the program to run and the preferred virtual console (actually, I think if you specify that, then if that console isn't available, the command fails).

[jayemef]

Interesting, thank you. I've read guides that referred to them as run levels, so I just always thought they were. Learn something new every day .

If knite75 is speaking about the same kind of "freeze up" that I have experienced, nothing works. CTRL+ALT+F2 doesn't even work. The mouse and keyboard are frozen as well along with the system. The only thing that seems to fix this is interrupting the power supply to the case, which causes an unclean shutdown.

Anyone happen to know what causes this? Or how to fix it when it happens?

[jayemef]

I actually experienced this as well... twice within a two day period. My screensaver (phosphor) includes a clock, so I knew exactly when the hangup occurred. I checked the logs, but nothing out of the ordinary appeared, so I'm not sure what caused the problem. I switched to another screensaver, just in case, but I REALLY doubt it had anything to do with it. I was able to turn off my system by holding the power button though. It's very strange that you couldn't. Perhaps you need to hold it longer?

jayemef: Great idea using a clock screensaver and going thru the logs. I have switched to the clock screensaver. Thank you for that info. Perhaps I do need to hold the power button longer, will try this next time.

For what it's worth, I'm experiencing the same problem here. Random and complete freeze (no mouse, keyboard, nothing); and the only recourse is the reset button. I've tested my memory with memtest86, installed gkrellm to monitor the CPU temperature (in case it was a factor), switched screensavers (even though the problem usually occurs as I'm working), even tried doing a fresh install of FC3 (I had upgraded from FC2 to FC3 previously). I have a clock on both my XFCE panel and gkrellm so I can see exactly at what time the system freezes but there is nothing in any of the logs at that time.

Very strange since the same hardware was flawless under FC2! Oh, the other thing I've tried is turning off acpi (acpi=off in grub.conf) and still no luck. The next thing I plan on trying is logging *everything* to a separate file (I currently do this but to a virtual console) with syslog by adding the following to /etc/syslog.conf:

*.* /var/log/complete.log

I'll see what I get with that and post back if I find anything out.

It might also help to know exactly which apps were running and what work was being done at the time the freeze occured.
This would help us track down a possible bug in a single app that causes the freeze. I, also, will keep a close eye on my system and post what info I find.

[ltam]

My Fedora Core 3 also freezes up sometimes. After some time, it unfreezes itself.