Kernel 6.6.87 compiled in Easy Daedalus

April 20, 2025 — BarryK

This morning, posted about compiling kernel version 6.12.23:

Kernel 6.12.23 in Easy Daedalus without AVS — April 20, 2025

But, frustrating; see this thread:

https://forum.puppylinux.com/viewtopic.php?t=14311

One frustration with the 6.12.x kernel, is some traditional Intel audio drivers have been removed, replaced by AVS. It seems, disabling AVS does not bring back those traditional drivers.

I commented in that forum thread, that the aufs developer will stop supporting the 6.6 kernel soon. My previous experiments with overlayfs have been bad news, but I'm going to give it another go; I think, see something that might have caused the problem.

So, have compiled 6.6.87 with overlayfs enabled. There was some discussion on the forum awhile back, about what configure options to enable. I asked Google, and "Generative AI" gave this answer:

For optimal performance and functionality with Overlay Filesystems, especially in container environments, the following kernel configuration options are generally recommended:
1. CONFIG_OVERLAY_FS: This is the core option to enable OverlayFS support in the kernel.
2. CONFIG_OVERLAY_FS_REDIRECT_DIR: Enabling this option (CONFIG_OVERLAY_FS_REDIRECT_DIR=y) makes OverlayFS behave more like a standards-compliant filesystem. It ensures that directory renaming operations on lower or merged directories do not result in an "Invalid cross-device link" error.
3. CONFIG_OVERLAY_FS_INDEX: This option (CONFIG_OVERLAY_FS_INDEX=y) is also recommended for standards compliance. It prevents hard link "breaking" when a file with multiple hard links is copied up into the upper layer.
4. CONFIG_OVERLAY_FS_XINO_AUTO: Enabling this (CONFIG_OVERLAY_FS_XINO_AUTO=y) is highly recommended as it helps maintain consistent behavior for stat and readdir operations across different layers and filesystems.
5. CONFIG_OVERLAY_FS_METACOPY: Enabling this (CONFIG_OVERLAY_FS_METACOPY=y) can significantly improve performance for operations like recursive chmod and other file attribute changes.
In Summary:
To enable OverlayFS, enable the core CONFIG_OVERLAY_FS, and for better compatibility and performance, enable CONFIG_OVERLAY_FS_REDIRECT_DIR, CONFIG_OVERLAY_FS_INDEX, CONFIG_OVERLAY_FS_XINO_AUTO, and CONFIG_OVERLAY_FS_METACOPY.

Which means, I configured the kernel like this:

  <*> Overlay filesystem support
    -*-   Overlayfs: turn on redirect directory feature by default     CONFIG_OVERLAY_FS_REDIRECT_DIR
    [ ]   Overlayfs: follow redirects even if redirects are turned off
    [*]   Overlayfs: turn on inodes index feature by default           CONFIG_OVERLAY_FS_INDEX
    [*]   Overlayfs: auto enable inode number mapping                  CONFIG_OVERLAY_FS_XINO_AUTO
    [*]   Overlayfs: turn on metadata only copy up feature by default  CONFIG_OVERLAY_FS_METACOPY
    [ ]   Overlayfs: turn on extra debugging checks (NEW)

There is a github project that has lots of example kernel configs:

https://github.com/nyrahul/linux-kernel-configs

...looking through some of them, it looks like only Arch Linux has the same overlayfs config choices. The others only have "follow redirects even if redirects are turned off" enabled and all the others disabled. Hmmm.

Looks like the next Easy Daedalus will stay with the 6.6 kernel. Next up, plan to experiment again with overlayfs.

Tags: easy