[Bug 1862300] Re: "systemctl kexec" reboots

[Alex Badea]

Turns out, systemd's shutdown implementation fork/execs the kexec binary
from kexec-tools; this is missing from the /run/initramfs finalrd.
systemd then falls through to reboot:
https://github.com/systemd/systemd/blob/a859abf062cef1511e4879c4ee39c6036ebeaec8/src/shutdown/shutdown.c#L557

One way to fix it might be for finalrd to "copy_exec /sbin/kexec" if it
exists.  Alternatively, the kexec-tools package might ship a finalrd
hook instead.

** Also affects: finalrd
   Importance: Undecided
       Status: New

** Project changed: finalrd => kexec-tools (Ubuntu)

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https://bugs.launchpad.net/bugs/1862300

Title:
  "systemctl kexec" reboots

Status in finalrd package in Ubuntu:
  New
Status in kexec-tools package in Ubuntu:
  New

Bug description:
  After the introduction of finalrd, "systemctl kexec" (with a kernel
  preloaded by "kexec -l ...") no longer kexec()s -- it reboots instead.

  Can be reproduced for example using a livecd (say, xubuntu-18.04
  -desktop-amd64.iso):

  sudo -i
  apt-get update
  apt-get install kexec-tools finalrd
  systemctl start finalrd  # optional
  kexec -l /cdrom/casper/vmlinuz
  systemctl kexec

  Expected results: the system kexec's into the kernel and panics (due
  to lack of /init, since we haven't given it an initrd).

  Actual results: the system reboots (e.g. the livecd's bootloader menu
  runs).

  
  If we don't install "finalrd" above, kexec works normally.

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