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.
A Debian user has recently discovered that systemd prevents the skipping of fsck while booting:
With init, skipping a scheduled fsck during boot was easy, you just pressed Ctrl+c, it was obvious! Today I was late for an online conference. I got home, turned on my computer, and systemd decided it was time to run fsck on my 1TB hard drive. Ok, I just skip it, right? Well, Ctrl+c does not work, ESC does not work, nothing seems to work. I Googled for an answer on my phone but nothing. So, is there a mysterious set of commands they came up with to skip an fsck or is it yet another flaw?
One user chimed in with a hack to work around the flaw, but it involved specifying an argument on the kernel command line. Another user described this so-called "fix" as being "Pretty damn inconvenient and un-discoverable", while yet another pointed out that the "fix" merely prevents "systemd from running fsck in the first place", and it "does not let you cancel a systemd-initiated boot-time fsck which is already in progress."
Further investigation showed that this is a known bug with systemd that was first reported in mid-2011, and remains unfixed as of late December 2014. At least one other user has also fallen victim to this bug.
How could a severe bug of this nature even happen in the first place? How can it remain unfixed over three years after it was first reported?