Kernels

Choosing one

A_KERNEL=Arctic-base-kernel

`Arctic-base-kernel`	the default. Linux 7.1.3, broad hardware support, most drivers as modules.
`Arctic-kernel`	Linux 6.12 LTS with the ZEN patchset merged on top.
`Arctic-libre-kernel`	no binary blob loading, no nonfree microcode.
`Arctic-small-kernel`	monolithic, no module loader, no initramfs needed. Fast boot, fixed hardware.
`Arctic-rt-kernel`	realtime preemption.
`Arctic-hardened-kernel`	hardening options turned up.

More than one can be installed at once; the bootloader lists each.

Arctic-kernel

A real fork, not a config change: github.com/apiwo/arctic-kernel. Linux 6.12 LTS with the ZEN patchset merged on top, plus an Arctic patch of its own.

What ZEN brings:

PDS and BMQ alternate schedulers
PCIe ACS override, for splitting IOMMU groups when passing a GPU through
ntsync — Wine and Proton synchronisation primitives
vhba — virtual SCSI host, for CD emulation
inlined futex fast paths, scheduler, TCP and cpufreq tuning

The Arctic patch on top raises default readahead to 512 KiB.

The merge was reconciled by hand against 83 upstream point releases of drift (6.12.17 to 6.12.100). What applied cleanly, what needed rework and what was dropped is written down honestly in the repo's PATCHES.md — including the one hunk that was dropped rather than guessed at.

The kernel Arctic ships is built with the same configuration Arctic-base-kernel uses, so the difference between them is the patchset, not the options.

The Arctic kernel configuration

Both kernels start from the distribution config and apply the same delta, for reasons worth knowing:

No BTF, no DWARF, no debuginfo. Across 4,800 modules that costs hours of build time and hundreds of megabytes on an installer image.
No module signing, no lockdown. Nothing is signed at build time; alpm verifies packages instead.
Storage and bus controllers built in, not modular. SATA, NVMe, USB, virtio, SCSI. The initramfs has to reach the boot medium before it can load a single module, so these cannot be modules themselves.
Filesystems built in. ext4, btrfs, xfs, vfat, iso9660, squashfs, overlayfs — the live ISO mounts a squashfs under an overlay before any module is available.
Framebuffer and simpledrm built in, so there is a console before graphics drivers load.

Arctic-small-kernel additionally disables the module loader entirely: everything it can do, it does without modules, and it needs no initramfs.

Building a kernel yourself

git clone https://github.com/apiwo/arctic-kernel
cd arctic-kernel
container/build.sh Default-config/config default bzImage modules

The build runs inside bubblewrap: the host toolchain bound read-only, no network, and the build's own output directory the only writable path. No docker or podman needed.

Four configurations ship: Default-config, Hardened-config, Small-config, RT-config.

To build it as an Arctic package instead, with Arctic's own configuration, see building from source.

Microcode and firmware

A_MICROCODE=auto     # or intel, amd, none

auto reads /proc/cpuinfo and installs intel-ucode or amd-ucode. Firmware comes from linux-firmware, which Arctic-libre-kernel deliberately skips.

Changing kernel later

The kernel is a package like any other, so it is declared like one:

SYS_PACKAGES="
	Arctic-kernel
	...
"

arctic-rebuild

Which means a kernel change is a generation, and a kernel that does not boot is one boot-menu entry away from being undone. See generations.

More: arctic linux docs · install · declarative configuration · generations and rollback · init systems · packages (alpm) · desktops and audio · ephemeral shells · musl · building from source