[Bug 1942260] Re: compress firmware in /lib/firmware

[Adrien Nader]

Have you tried environment variables?


>From the xz manpage:

ENVIRONMENT
       xz parses space-separated lists of options from the  environment  vari‐
       ables XZ_DEFAULTS and XZ_OPT, in this order, before parsing the options
       from the command line.  Note that only options are parsed from the  en‐
       vironment  variables; all non-options are silently ignored.  Parsing is
       done with getopt_long(3) which is used also for the command line  argu‐
       ments.

       XZ_DEFAULTS
              User-specific or system-wide default options.  Typically this is
              set in a shell initialization script to enable xz's memory usage
              limiter  by default.  Excluding shell initialization scripts and
              similar special cases, scripts must never set  or  unset  XZ_DE‐
              FAULTS.

       XZ_OPT
              This is for passing options to xz when it is not possible to set
              the options directly on the xz command line.  This is  the  case
              when xz is run by a script or tool, for example, GNU tar(1):

                     XZ_OPT=-2v tar caf foo.tar.xz foo

              Scripts  may use XZ_OPT, for example, to set script-specific de‐
              fault compression options.  It is  still  recommended  to  allow
              users to override XZ_OPT if that is reasonable.  For example, in
              sh(1) scripts one may use something like this:

                     XZ_OPT=${XZ_OPT-"-7e"}
                     export XZ_OPT


>From the zstd manpage:

   Environment Variables
       Employing environment variables to set parameters has security implica‐
       tions.   Therefore,   this   avenue   is  intentionally  limited.  Only
       ZSTD_CLEVEL and ZSTD_NBTHREADS are currently supported.  They  set  the
       compression  level and number of threads to use during compression, re‐
       spectively.

       ZSTD_CLEVEL can be used to set the level between 1 and 19 (the "normal"
       range).  If the value of ZSTD_CLEVEL is not a valid integer, it will be
       ignored with a warning message. ZSTD_CLEVEL just replaces  the  default
       compression level (3).

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https://bugs.launchpad.net/bugs/1942260

Title:
  compress firmware in /lib/firmware

Status in initramfs-tools package in Ubuntu:
  Fix Released
Status in linux-firmware package in Ubuntu:
  Confirmed
Status in linux-firmware-raspi2 package in Ubuntu:
  Confirmed

Bug description:
  -- initramfs-tools

  [Impact]

   * linux supports xz compressed linux-firmware which saves disk space.
  In focal, initramfs-tools only knows how to included uncompressed
  firmware files (even when kernel supports loading compressed ones).
  Newer releases of linux-firmware may use compressed firmware files
  only, in such cases it would be nice for focal's initramfs-tools to
  support compressed firmware files in case of partial or incomplete
  upgrades (i.e. linux-firmware force installed or upgraded, without
  newer initramfs-tools). The proposed changes to initramfs-tools are
  backwards and forwards compatible, they prefer to include uncompressed
  firmware files; and if missing, include compressed firmware files in
  their uncompressed form. Thus maintaining compatibility with any
  kernels, irrespective of compressed/uncompressed firmware inputs.

  [Test Plan]

   * Compress all files shipped by linux-firmware with xz

   * Rebuild initrd

   * Check that all the same firmware files are still included in the
  initramfs, in their uncompressed form as before

  [Where problems could occur]

   * This SRU is precautionary to prevent accidental installation of
  compressed linux-firmware from generating incorrect initramfs. It
  should be noted that whilst initramfs-tools would create a compatible
  initramfs with any kernels, pre-v5.3 kernels do not support xz
  compressed firmware files at runtime. Mixing this new initramfs with
  compressed firmwares and pre 5.3 kernels may lead to expectations of
  supporting compressed firmware files with them only working at initrd
  stage and not at runtime.

  [Other Info]
  Original bug report

  Some facts:
   - The linux kernel has supported loading xz compressed firmware since 5.3
   - The size of /lib/firmware in impish is ~650Mb (and growing)
   - The compressed size of firmware could be ~230Mb

  It would be nice to install compressed firmware to save space.

  Here are the plans from the Fedora project:
  https://fedoraproject.org/wiki/Changes/CompressKernelFirmware

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