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FS#46591 - [linux-firmware] microcode reload via tmpfiles.d fails in container

Attached to Project: Arch Linux
Opened by Johannes Ernst (jernst) - Wednesday, 07 October 2015, 03:00 GMT
Last edited by Jonas Witschel (diabonas) - Wednesday, 22 June 2022, 11:57 GMT
Task Type Bug Report
Category Packages: Core
Status Assigned   Reopened
Assigned To Laurent Carlier (lordheavy)
Architecture All
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 0%
Votes 0
Private No


The PKGBUILD file contains this:

echo 'w /sys/devices/system/cpu/microcode/reload - - - - 1' \

which works fine on a regular physical box, but not in a Linux container. There's a thread here [1] on the systemd-devel list discussing this.

Error message:

Failed to create file /sys/devices/system/cpu/microcode/reload: Read-only file system

Perhaps the way to fix this is to have a separate systemd.service for this (instead of wedging it into tmpfiles)) which is conditional on not running in a container (using key word ConditionVirtualization per [2])

[2] man systemd.unit

This task depends upon

Comment by Evangelos Foutras (foutrelis) - Wednesday, 07 October 2015, 23:59 GMT
If the container booted its own kernel, it would be a reasonable requirement to have a writable /sys.

Since you're using systemd-nspawn, you don't need to have a kernel installed in the container; simply remove the linux and linux-firmware packages ('pacman -Rs linux' should get rid of all unneeded packages).
Comment by nl6720 (nl6720) - Wednesday, 22 June 2022, 11:56 GMT
Linux 5.19 will not have /sys/devices/system/cpu/microcode/reload unless MICROCODE_LATE_LOADING (renamed from MICROCODE_OLD_INTERFACE) is enabled. Upstream considers late loading dangerous so /usr/lib/tmpfiles.d/linux-firmware.conf should be removed.

See .
Comment by nl6720 (nl6720) - Tuesday, 16 August 2022, 10:34 GMT
With linux 5.19.1.arch2-1 in core, /sys/devices/system/cpu/microcode/reload is gone as predicted. /usr/lib/tmpfiles.d/linux-firmware.conf is now entirely useless.