[Bug 1800562] Re: Remove obsolete "nousb" option in kdump command-line for newer kernels

[Simon Quigley]

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https://bugs.launchpad.net/bugs/1800562

Title:
  Remove obsolete "nousb" option in kdump command-line for newer kernels

Status in makedumpfile package in Ubuntu:
  Opinion
Status in makedumpfile source package in Xenial:
  In Progress
Status in makedumpfile source package in Bionic:
  In Progress
Status in makedumpfile source package in Cosmic:
  In Progress
Status in makedumpfile source package in Disco:
  Opinion

Bug description:
  [Impact]
  Crash kernels include an obsolete "nousb" parameter by default, which can cause confusion since it's been deprecated in newer kernel versions.

  [Description]
  Since kernel v4.5, the correct parameter to disable USB subsystem initialization is "usbcore.nousb" always (instead of "nousb" in case the subsystem is built-in). This was changed by commit 097a9ea0e48 ("usb: make "nousb" a clear module parameter").

  We need to take this into account in kdump-tools, or else we may boot
  with USB in kdump even the command-line appears to be saying the
  opposite.

  This affects Xenial onwards, since the system may be running an HWE or
  other supported v4.5+ kernel.

  [Test Case]
  1) Deploy a Disco VM e.g. with uvt-kvm
  2) Install the kdump-tools package
  3) Run `kdump-config test`and check for the 'nousb' parameter:

  $ kdump-config test
  ...
  kexec command to be used:
    /sbin/kexec -p --command-line="BOOT_IMAGE=/boot/vmlinuz-4.15.0-45-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0 nr_cpus=1 systemd.unit=kdump-tools.service irqpoll nousb ata_piix.prefer_ms_hyperv=0" /var/lib/kdump/vmlinuz

  [Regression Potential]
  The regression potential is extremely low, since it doesn't need any changes in makedumpfile code and we're only removing an already ineffective parameter from the crashkernel cmdline. Nonetheless, patches will be tested with autopkgtests and normal kdump use-case scenarios.

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