[Bug 1535840] Re: systemd ignoring /etc/modules due to blacklist

[James Cuzella]

Confirmed this still exists in 22.04 (Jammy Jellyfish), with symptoms
being SystemD booting always into "degraded" state because wdmd.service
(Watchdog Multiplexing Daemon) will always fail due to missing watchdog
kernel module(s).

Check this is the case with:

    sudo systemctl status
    sudo systemctl list-units --failed 

The solution suggested by @ishworgurung works to allow iTCO_wdt (and other watchdogs) to be loaded by the kernel during boot appropriately.  Then, wdmd.service starts up successfully and SystemD enters successful "running" state (assuming all other SystemD services are working properly).
However, every kernel package update will place another blacklist file in /lib/modprobe.d/blacklist_linux_$(uname -r).conf.  So this is only a temporary workaround until these modules are not blacklisted by default.

The blacklist files are part of linux-modules-$(uname -r) package(s).
Therefore, this bug should be listed as also affecting Linux kernel
source packages for Ubuntu.

    $ dpkg -S /lib/modprobe.d/blacklist_linux_*.conf
    linux-modules-5.15.0-74-generic: /lib/modprobe.d/blacklist_linux_5.15.0-74-generic.conf
    linux-modules-5.4.0-149-generic: /lib/modprobe.d/blacklist_linux_5.4.0-149-generic.conf
    # ^^ These packages own /lib/modprobe.d/blacklist_linux*.conf files

    $ apt-cache show linux-modules-$(uname -r) | grep -C5 Source: | sed -e 's/^/    /'
    Package: linux-modules-5.15.0-74-generic
    Architecture: amd64
    Version: 5.15.0-74.81
    Priority: optional
    Section: kernel
    Source: linux
    Origin: Ubuntu
    Maintainer: Ubuntu Kernel Team <kernel-team at lists.ubuntu.com>
    Bugs: https://bugs.launchpad.net/ubuntu/+filebug
    Installed-Size: 123864
    Depends: linux-image-5.15.0-74-generic | linux-image-unsigned-5.15.0-74-generic
    ## ^^ Part of Linux APT package(s) in Ubuntu

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https://bugs.launchpad.net/bugs/1535840

Title:
  systemd ignoring /etc/modules due to blacklist

Status in systemd package in Ubuntu:
  Opinion

Bug description:
  I tried the daily build of 16.04 32-bit to test out the watchdog
  daemon code. Usually (Ubuntu 10.04-14.04) I add the watchdog module in
  /etc/modules so it is loaded at boot-time, as watchdog timer modules
  are not normally auto-loaded due to the risk of an unexpected reboot.

  However I now find that systemd is choosing to ignore my command to
  load the module in /etc/modules since it appears in the watchdog
  blacklist. Typical syslog entries look like this:

  Jan 19 16:46:14 ubuntu systemd-modules-load[337]: Module 'softdog' is blacklisted
  Jan 19 17:53:23 ubuntu systemd-modules-load[342]: Module 'softdog' is blacklisted

  This is just dumb! I have explicitly told the system to load the
  module, an action that works perfectly well using modprobe or by
  adding it to the start script for the watchdog, and yet systemd
  chooses to override that because of the blacklist for auto-loaded
  modules (in this case in /etc/modprobe.d/blacklist-watchdog.conf).

  $ lsb_release -rd
  Description:	Ubuntu Xenial Xerus (development branch)
  Release:	16.04

  $ apt-cache policy systemd
  systemd:
    Installed: 228-4ubuntu1
    Candidate: 228-4ubuntu1
    Version table:
   *** 228-4ubuntu1 500
          500 http://us.archive.ubuntu.com/ubuntu xenial/main i386 Packages
          100 /var/lib/dpkg/status

  What I expect to happen is modules added to /etc/modules are loaded at
  boot time, and not subject to the blacklist for hardware detect /
  automatic loading.

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