GQ-02 : What do I do when my system stops responding?

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GQ-02 : What do I do when my system stops responding?

 

Before you get to the point of needing to press the reset button, you might want to read this.

 

Author Tom Berger.

The Magic SysRq Key

 

This feature allows you to do some basic maintenance tasks even if the rest of the system isn't responding. It is enabled by default on Mandrake Linux. In particular, it allows you to shutdown your system properly, thus avoiding the risk of file system corruption when simply turning the machine off with media still being mounted.

 

The 'SysRq' sequence involves pressing three keys at once, theleft ALT key, the 'SysRq' key (also labeled 'PrtSc' or 'F13') and a letter key:

 

1.

 

<ALT> <SysRq> <r> puts the keyboard in 'raw' mode.

This might be helpful in cases where the graphical interface does not respond to keyboard or mouse commands any more. Having pressed that sequence, press <ALT> <CTRL> <BACKSPACE> simultaneously. This will try to kill the X server and drops you onto the console (i.e. it's the emergency key combination to switch from runlevel 5 to runlevel 3).

2.

 

<ALT> <SysRq> <s> attempts to write all unsaved data to disk ('sync' the disk) to prevent file corruption.

3.

 

<ALT> <SysRq> <e> sends a termination signal to all processes, except for 'init'.

4.

 

<ALT> <SysRq> <i> sends a kill signal to all processes, except for init, thus terminating all processes which ignored the termination signal.

5.

 

<ALT> <SysRq> <u> remounts all mounted file systems read-only. This prevents file system corruption.

6.

 

<ALT> <SysRq> <b> reboots the system. Alternatively, replace the 'b' with an 'o' to turn the machine off.

 

If you look at this sequence, you see that you are - apart from the first step - actually emulating the 'init' shutdown process. Therefore it is important that you press these sequences in the correct order (e.g. that you 'sync' the drives before remounting them): Raw -Sync - tErm - kIll -Umount - reBoot. A possible mnemonic phrase: 'Raising Skinny Elephants Is Utterly Boring'. Mandrake Linux user Louis suggested this phrase, which is a bit more on topic: 'Remembering the Sequence Entirely Is Useful Buddy'.

 

Reference Link(s):

http://mandrakeusers.org/index.php?showtopic=993

http://www.mandrakeuser.org/docs/admin/arecov4.html

http://www.mandrakeuser.org/docs/mdoc/ref/...tem-freeze.html