Linux
Table of Contents
1. Resetting
Under certain conditions, it is possible to reset a linux machine by
force just by echoing commands to the file /proc/sysrq-trigger.
Check the output of cat /proc/sys/kernel/sysrq to see what is possible:
| base 10 | base 16 | effect |
|---|---|---|
2 |
0x2 |
enable control of console logging level |
4 |
0x4 |
enable control of keyboard (SAK, unraw) |
8 |
0x8 |
enable debugging dumps of processes etc. |
16 |
0x10 |
enable sync command |
32 |
0x20 |
enable remount read-only |
64 |
0x80 |
enable signalling of processes (term, kill, oom-kill) |
128 |
0x40 |
allow reboot/poweroff |
256 |
0x100 |
allow nicing of all RT tasks |
Sadly Arch linux seems to allow only for the sync command.
Sources differ on if one needs the panic set or not. If so:
echo 1 > /proc/sys/kernel/panic
And then
echo c > /proc/sysrq-trigger
Some of the commands:
| command | effect |
|---|---|
b |
Immediately reboot the system without syncing or unmounting disks. |
s |
Shut the system off (if configured and supported). |
o |
Attempt to sync all mounted filesystems. |
Written after reading this blog post.
2. networking
- How to see how many sockets a process is using
watch -n 1 "netstat --all --program | grep 'sbcl'"