[Bug 1832108] Re: unmkinitramfs fails with lz4 compressed initrds

[Balint Reczey]

This seems to be working on Bionic:

root at bb-qemu:~#  echo asd | lz4 > asd
root at bb-qemu:~# file asd
asd: LZ4 compressed data (v1.4+)
root at bb-qemu:~# lz4cat -t asd 
root at bb-qemu:~# echo $?
0


** Also affects: initramfs-tools (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Changed in: initramfs-tools (Ubuntu Bionic)
       Status: New => Invalid

** Also affects: initramfs-tools (Ubuntu Disco)
   Importance: Undecided
       Status: New

** Also affects: initramfs-tools (Ubuntu Cosmic)
   Importance: Undecided
       Status: New

** Changed in: initramfs-tools (Ubuntu Cosmic)
       Status: New => Confirmed

** Changed in: initramfs-tools (Ubuntu Disco)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1832108

Title:
  unmkinitramfs fails with lz4 compressed initrds

Status in initramfs-tools package in Ubuntu:
  Fix Released
Status in initramfs-tools source package in Bionic:
  Invalid
Status in initramfs-tools source package in Cosmic:
  Confirmed
Status in initramfs-tools source package in Disco:
  Confirmed
Status in initramfs-tools package in Debian:
  Unknown

Bug description:
  [Impact]

   * Cannot unpack initrds compressed with lz4 due to changes in lz4

  [Test Case]

  $ sudo apt install initramfs-tools lz4 file
  $ mkinitramfs -c lz4 -o foo.img
  $ lsinitramfs foo.img
  cpio: premature end of archive

  [Regression Potential]

   * New lz4cat is more strict w.r.t. enforcing file name extensions,
  thus the fix is to feed a stream to lz4cat instead of asking it to
  open a file. The performance impact should be similar between both
  methods of reading file contents during ls/unmk-initramfs time.

  [Other Info]

  Original bug report:

  unmkinitramfs fails with lz4 compressed initrds

  Note:
  $ lz4cat -t unmkinitramfs_Cz6Yl9
  File extension doesn't match expected LZ4_EXTENSION (.lz4); will not process file: unmkinitramfs_Cz6Yl9

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