[Bug 1589394] [NEW] "debug" kernel parameter causes Denial of Service

[TJ]

Public bug reported:

15.10/16.04 amd64

With the Linux kernel's "debug" parameter set systemd spams the logs to
such a degree that boot fails with the plymouth progress indicator
constantly cycling, only tty1 available, and no clear indication from
the last messages displayed on console as to why.

It's not even clear if the system has transitioned from initrd to rootfs
at this point and there's no way to interact. Certainly no log file
residues are found on subsequent non-debug boots which infers the hang
may be during initrd.

Leaving aside the unresolved bug of systemd adopting the Linux 'debug'
parameter, and thus being the direct cause of this, the complete failure
to boot as a result is a serious regression and a Denial of Service.
Needing to alter the Linux command-line to use "loglevel=7" is a
distasteful workaround.

A boot without "debug" using the same GRUB menuitem starts fine which
suggests the systemd debug-level logging is the direct cause.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1589394

Title:
  "debug" kernel parameter causes Denial of Service

Status in systemd package in Ubuntu:
  New

Bug description:
  15.10/16.04 amd64

  With the Linux kernel's "debug" parameter set systemd spams the logs
  to such a degree that boot fails with the plymouth progress indicator
  constantly cycling, only tty1 available, and no clear indication from
  the last messages displayed on console as to why.

  It's not even clear if the system has transitioned from initrd to
  rootfs at this point and there's no way to interact. Certainly no log
  file residues are found on subsequent non-debug boots which infers the
  hang may be during initrd.

  Leaving aside the unresolved bug of systemd adopting the Linux 'debug'
  parameter, and thus being the direct cause of this, the complete
  failure to boot as a result is a serious regression and a Denial of
  Service. Needing to alter the Linux command-line to use "loglevel=7"
  is a distasteful workaround.

  A boot without "debug" using the same GRUB menuitem starts fine which
  suggests the systemd debug-level logging is the direct cause.

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