Public bug reported:
So I have a fairly uncommon use case, so I'm assuming that is why this
hasn't been reported..
As background I am running into this problem in the midst of upgrading
from noble to questing. (I'm not sure if something in the upgrade path
was supposed to catch this incompatibility, but -- if so -- it did not.)
That shouldn't be necessary to reproduce this bug, however.
I have both 3cpio and pigz installed, and `COMPRESS=gzip` set in
`/etc/initramfs-tools/initramfs.conf`.
It seems that any attempt to build an initramfs image in such
circumstances will result in the following error:
===
update-initramfs: Generating /boot/initrd.img-6.14.0-34-generic
3cpio: Error: Failed to create 'cpio on stdout': line 2387: Unknown compression
format: pigz
E: mkinitramfs failure 3cpio 1
update-initramfs: failed for /boot/initrd.img-6.14.0-34-generic with 1.
===
A quick visual inspection of the man page for 3cpio and the contents of the
/usr/sbin/mkinitramfs script explain why:
a) the man page for 3cpio doesn't list 'pigz' as a valid compression format
b) mkinitramfs uses pigz as the value for the compression format if it is
initially set to gzip and the pigz binary is found in PATH
c) mkinitramfs uses 3cpio in lieu of cpio if the 3cpio binary is found in PATH
d) mkinitramfs performs no check for when (b) and (c) are both true
The obvious temporary workaround would be to either change the initramfs
compression format, or else uninstall one of the packages (assuming no
dependency issues preclude the latter).
As for versions installed, I have the latest:
===
root@vastdesk:~# dpkg -l 3cpio initramfs-tools-core pigz
ii 3cpio 0.10.2-0ubuntu1 amd64 Manage initrd cpio
archives
ii initramfs-tools-core 0.150ubuntu3 all generic modular initramfs
generator (core tools)
ii pigz 2.8-1 amd64 Parallel Implementation
of GZip
root@vastdesk:~# lsb_release -rd
No LSB modules are available.
Description: Ubuntu 25.10
Release: 25.10
===
** Affects: initramfs-tools (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2130550
Title:
mkinitramfs incorrectly attempts to use incompatible compression
format pigz with 3cpio
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