Initial version of SteamOS kdump

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

README.md

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+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  Copyright (c) 2021 Valve.
+#
+#  Code by Guilherme G. Piccoli <gpiccoli@igalia.com>
+#
+#
+#  ###########################################################################
+#  ############################  SteamOS Kdump  ##############################
+#  ###########################################################################
+#
+#  This is the first version of SteamOS Kdump infrastructure. The goal is to
+#  collect data whenever a kernel crash is detected. There is a lightweight
+#  collection, that only grabs dmesg, and a more complete setting to grab the
+#  whole (compressed) vmcore. The tunnings are available at /etc/default/kdump.
+#
+#  After installation and a reboot, things should be all set EXCEPT for GRUB
+#  config - please check the CAVEATS/INSTRUCTIONS section below. Notice the
+#  package is under active development, this one being a kind of "Proof Of Concept"
+#  still - improvements are expected in the near future. Thanks for testing!!!
+#
+#
+#  CAVEATS / INSTRUCTIONS
+#  ###########################################################################
+#  (a) For now, we  don't automatically edit any GRUB config, so the minimum
+#  necessary action after installing this package is to add "crashkernel=160M"
+#  to your GRUB config in order subsequent boots pick this setting and do reserve
+#  the memory, or else kdump cannot work. The memory amount was empirically
+#  determined - 128M wasn't enough and 144M is unstable, so 160M seems good enough.
+#
+#  (b) It requires (obviously) a RW rootfs - we've used tune2fs in order to make
+#  it read-write, since it's RO by default. Also, we assume the nvme partition
+#  scheme is default across all versions and didn't change with new updates
+#  for example - kdump relies in mounting partitions, etc.
+#
+#  (c) Due to a post-transaction hook executed by libalpm (90-dracut-install.hook),
+#  unfortunately after installing the kdump-steamos package *all* initramfs images
+#  are recreated - this is not necessary, we're thinking on how to prevent that,
+#  but for now be prepared: the installation take some (long) minutes due to that ={
+#
+#  (d) Unfortunately makedumpfile form Arch Linux is not available on official
+#  repos, only in AUR - and it doesn't build with zstd, which allows great and
+#  fast compression. So, we're hereby _packing the binary_ with all the scripts,
+#  which is a temporary workaround and should be resolved later - already started
+#  to "lobby" for package inclusion in the official channels and also we're trying
+#  to to add zstd support:
+#  https://aur.archlinux.org/packages/makedumpfile/#comment-841333
+#
+#
+#  TODOs (for now - we expect to have more after some testing by the colleagues)
+#
+#  (1) We'd like to be able to automatically edit GRUB and recreate its config
+#  file - after some future discussion on the proper parameters, this is expected
+#  to be added to the package.
+#
+#  (2) Hopefully we can fix/prevent the unnecessary re-creation of all initramfs
+#  images - this happens due to our package installing files on /usr/lib/dracut/modules.d
+#  which is a trigger for this initramfs recreation.
+#
+#  (3) We have a "fragile" way of determining a mount point required for kdump;
+#  this is something to improve in order to make the kdump more reliable.
+#
+#  (4) Add a more reliable reboot mechanism - we had seen issues with "reboot -f"
+#  in the past and relying in sysrq reboot as a quirk managed to be a safe option,
+#  so this is something to think about here. Should be easy to implement.
+#
+#  (5) Maybe a good idea would be to allow creating the minimum image for any
+#  specified kernel, not only for the running one (which is what we do now).
+#  Low-priority idea, easy to implement.
+#