Abstract
When stuck in a “freeze”, your computer doesn't respond to commands anymore and input devices such as keyboard and mouse seem to be blocked. This is a worst-case scenario and could mean that you have a very severe error in either your configuration, your software or your hardware. We will show you how to deal with this annoying situation.
In the case of a system freeze, your top priority should be trying to shutdown your system properly. We assume you are running under X. So try these steps consecutively:
Try to kill the X server by pressing the Ctrl-Alt-Backspace keys.
Try to switch to
another console by pressing the
Ctrl-Alt-Fn keys (where
n
is the console number, from 1 to
6). If you succeed, login as root
and issue the
command: kill -15 $(pidof X) or the
command kill -9 $(pidof X), if the
first command shows no effect. Check with
top to see if X is still
running.
If you are part
of a local network, try to use ssh to connect into your
machine from another. It is advisable to
ssh into the remote machine as an
unprivileged user and then use the su command
to become root
.
If the system doesn't respond to any of these steps, you have to go through the SysRq (System Request) sequence. The SysRq sequence involves pressing and holding three keys at once: the left Alt key, the SysRq key (labeled Print Screen on older keyboards) and a letter key.
Alt-SysRq-R puts the keyboard in “raw” mode. Now try pressing Alt-Ctrl-Backspace again to kill X. If that doesn't work, carry on.
Alt-SysRq-S attempts to write all unsaved data to disk (“sync” the disk).
Alt-SysRq-E sends a
termination signal to all processes, except for
init
.
Alt-SysRq-I sends a
kill signal to all processes, except for
init
.
Alt-SysRq-U attempts to re-mount all mounted filesystems read-only. This removes the “dirty flag” and prevents a filesystem check upon reboot.
Alt-SysRq-B reboots the system. You might just as well press the “reset” button on your machine.
![]() | Note |
---|---|
Remember that this is a sequence, i.e. you have to press one combination after the other in the right order: Raw, Sync, tErm, kIll, Umount, reBoot[20]. Read the kernel documentation for more information on this feature. |
If none of the above helps, cross your fingers and press the “reset” switch on your machine. If you are lucky, GNU/Linux will just run a disk check upon reboot.
By all means, try to find out what causes these lockups because they can do severe damage to the filesystem. You might also want to consider using one of the journaling filesystems included in Mandriva Linux: ext3, reiserfs, etc. which handle such failures more gracefully. However, replacing ext2FS with reiserfs requires reformatting your partitions. You can use tune2fs -j /dev/hdaN to convert the filesystem in the Nth partition of the first IDE disk from ext2FS to ext3FS.