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posted by LaminatorX on Monday December 22 2014, @02:13AM   Printer-friendly
from the Man-what? dept.

As long time SoylentNews community member Marand observed during some recent discussion of severe systemd boot problems, it turns out that systemd disables the magic SysRq key.

The magic SysReq key is described at Wikipedia as:

[...] a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system's state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem.

A Fedora user who logged a bug report for this issue back in 2013 described the problem with systemd's unexpected and harmful default setting:

As systemd depends on many files on a rootfs, in case of any problems with rootfs, it is not able to do its basic function - control processes and (cleanly) shutdown/reboot when crtl-alt-del is pressed on local keyboard. As this is a feature, I'd like to ask to enable the sysrq by default on Fedora, otherwise it is not possible to reboot system even locally in case of emergency situation.

While that Fedora bug report is set to CLOSED NOTABUG, other Linux distros, like Mageia and Debian GNU/Linux, have restored the proper behavior.

Now that this problem has come to light, all Fedora users should evaluate whether or not they need to fix their systems to work around systemd's incorrect default setting. Users of other Linux distributions using systemd should also evaluate their systems, too, in case their distro has not yet fixed this unexpected bug.

 
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  • (Score: 1) by steveha on Monday December 22 2014, @07:15PM

    by steveha (4100) on Monday December 22 2014, @07:15PM (#128430)

    I think we can all agree that whether SystemD is a good thing or not, it is designed to do init-type tasks.

    The SystemD guys think that SystemD should legitimately be setting up the magic SysReq key. They picked a default value that "should be safe"... I don't know what that means but I guess it disables the magic SysReq key. I'll say it again: the default value disables the magic SysReq key.

    Another guy thinks that the magic SysReq key is special, and SystemD shouldn't set it. Some other config file should set it. Further discussion of the bug showed that SystemD guys don't agree.

    Okay, I'm trying to figure out why this is a top-level news story. If you have SystemD, you enable the magic SysReq key by editing a SystemD setup file. This is controversial... why?

    IMHO if you are letting SystemD manage your system, it should be no big deal to enable the magic SysReq key by editing a SystemD config file rather than some other config file.

    So, what have I missed here? Why is this a top-level story?

  • (Score: 2) by darkfeline on Monday December 22 2014, @10:13PM

    by darkfeline (1030) on Monday December 22 2014, @10:13PM (#128505) Homepage

    Obligatory SN Two Minutes Hate for systemd. Just as Poettering is fostering a cult of "My way or the highway", SN is fostering a cult of "systemd and Poettering are the devil".

    --
    Join the SDF Public Access UNIX System today!
  • (Score: 2) by tonyPick on Tuesday December 23 2014, @08:34AM

    by tonyPick (1237) on Tuesday December 23 2014, @08:34AM (#128617) Homepage Journal

    I think we can all agree that whether SystemD is a good thing or not, it is designed to do init-type tasks.

    Much as I've been avoiding this discussion this time around... Several people would disagree with you, and one of those people is Poeterring:

    It's not just an init system anymore, but the basic userspace building block to build an OS from

    From http://0pointer.de/blog/projects/the-biggest-myths.html [0pointer.de]

    See also: http://0pointer.net/blog/revisiting-how-we-put-together-linux-systems.html [0pointer.net]

    • (Score: 0) by Anonymous Coward on Tuesday December 23 2014, @08:45AM

      by Anonymous Coward on Tuesday December 23 2014, @08:45AM (#128618)

      How do you go from "It's not just an init system anymore" to "it is not designed to do init-type tasks"?

      Even if "it's not just an init system anymore" it's still an init system.