this post was submitted on 23 Jun 2026
25 points (96.3% liked)

Linux

15302 readers
372 users here now

A community for everything relating to the GNU/Linux operating system (except the memes!)

Also, check out:

Original icon base courtesy of lewing@isc.tamu.edu and The GIMP

founded 3 years ago
MODERATORS
Ategon@programming.dev
anzo@programming.dev
dwraf_of_ignorance@programming.dev
25
What is the magic sysreq combination? (piefed.blahaj.zone)
submitted 4 months ago* (last edited 4 months ago) by sem@piefed.blahaj.zone to c/linux@programming.dev
11 comments fedilink hide all child comments
 

Buried in the Wikipedia article is what I remember, with a note saying not to use it any more.

So what sysreq keys do you use to recover a non responsive system with a journaling file system?

Before the advent of journaled filesystems a common use of the magic SysRq key was to perform a safe reboot of a locked-up Linux computer (using the sequence of key presses indicated by the mnemonic REISUB), which lessened the risk of filesystem corruption. With modern filesystems, syncing and unmounting is still useful to force unflushed data to disk, but is no longer necessary to prevent filesystem corruption (and may increase the risk of corruption in case the lock-up is caused by the kernel being in a bad state).^[11]^ The default value of kernel.sysrq in distributions such as Ubuntu and Debian remains 176^[citation needed]^ (allowing the sync, unmount, and reboot functions) and 438^[12]^ (allowing the same functions plus loglevel, unraw, and nice-all-RT-tasks) respectively.

you are viewing a single comment's thread
view the rest of the comments
[–] BCsven@lemmy.ca 2 points 4 months ago* (last edited 4 months ago)

Hmm, I have a vague recollection of a setting to allow sysreq key combos or not.

Edit: Ahh, Rentlar notes it in their comment.

You should check ahead of time whether the value of /proc/sys/kernel/sysrq is not zero to be sure the Sysrq functions are enabled. If not, then in /etc/sysctl.d/99-sysctl.conf you can add the line kernel.sysrq = 1 to enable all features, or a higher number to enable select features.