The Axelera Metis is an M.2 Key M AI Processing Unit (AIPU) that connects over PCIe on the Exaviz Cruiser carrier board. It provides hardware-accelerated inference for workloads such as Frigate NVR object detection.
PCIe identifiers
| Attribute | Value |
|---|
| Vendor ID (metis-setup.sh) | 0x1f0f |
| Device ID (metis-setup.sh) | 0x0001 |
| Vendor ID (preflight / dracut rules) | 0x1e81 |
| PCI model name | AX2520 |
Two vendor IDs appear across the tooling: 0x1f0f is used in the udev rule written by metis-setup.sh, while 0x1e81 is the value checked by preflight.sh and used in the dracut udev rules. Use 0x1e81 for the accel subsystem rules and 0x1f0f for PCI subsystem rules.
Post-boot verification
After boot, confirm the Metis device is enumerated by the kernel:
Check PCI enumeration
Expected output:0001:00:00.0 Processing accelerators: Axelera AI AX2520
Check PCIe link speed
lspci -vvv -d 1e81: | grep -E "LnkCap|LnkSta"
Verify the device node symlink
The symlink must point to /dev/accel0 (or the assigned accel node). If missing, check that the udev rules are installed and run udevadm trigger. Group and udev setup
The axelera group controls access to the Metis device node. The setup script creates the group, installs the udev rule, and adds the frigate and hass service accounts.
Create the axelera group
The -r flag creates a system group. The || true in the script allows re-running safely if the group already exists. Install the udev rule
cat > /etc/udev/rules.d/99-axelera-metis.rules <<'EOF'
SUBSYSTEM=="pci", ATTR{vendor}=="0x1f0f", ATTR{device}=="0x0001", \
GROUP="axelera", MODE="0660", TAG+="systemd"
EOF
udevadm control --reload-rules
udevadm trigger
Add service users to the group
usermod -aG axelera frigate
usermod -aG axelera hass
/dev/axelera0 without elevated privileges.axelera.service systemd unit
axelera.service loads the device-tree overlay for the Metis at runtime by writing the DTBO into the kernel’s configfs overlay interface. This applies the overlay without requiring a reboot.
[Service]
ExecStartPre=/usr/bin/mkdir -p /sys/kernel/config/device-tree/overlays/axelera
ExecStart=/usr/bin/sh -c 'cat /lib/firmware/overlays/axelera-metis.dtbo \
> /sys/kernel/config/device-tree/overlays/axelera/dtbo'
systemctl enable --now axelera.service
OpenRC status helper
For OpenRC-based systems, ax_status.openrc provides a custom status_ai command:
#!/sbin/openrc-run
extra_commands="status_ai"
depend() {
need axelera-slammer
}
status_ai() {
if [ -e /dev/axelera0 ]; then
/usr/bin/ax_status
else
echo "Hardware not initialized."
return 1
fi
}
rc-service ax_status status_ai
axelera-watchdog OpenRC service
For OpenRC systems, axelera-watchdog runs axelera-stats-logger as a background daemon, logging AI chip health metrics to syslog every 60 seconds:
#!/sbin/openrc-run
name="Axelera Hardware Monitor"
description="Background watchdog for AI chip health"
command="/usr/bin/axelera-stats-logger"
command_args="--interval 60 --syslog"
command_background="yes"
pidfile="/run/${RC_SVCNAME}.pid"
depend() {
need dev
after axelera-slammer # Wait for the DTBO slammer to finish
}
start_pre() {
# Verify the AI chip actually exists before backgrounding
[ -e /dev/axelera0 ]
}
start_pre() hook prevents the watchdog from starting if /dev/axelera0 is absent, avoiding a noisy failure on systems where the Metis has not yet been configured.
Dracut module
The 95rpi-hardware dracut module embeds the Exaviz Cruiser and Axelera Metis device-tree overlays into the initramfs. This ensures the overlays are available for early userspace hardware bring-up before the root filesystem is mounted.
#!/bin/bash
# /usr/lib/dracut/modules.d/95rpi-hardware/module-setup.sh
check() {
# Only include this if we are on an ARM64 RPi
[[ "$(uname -m)" == "aarch64" ]] || return 1
return 0
}
depends() {
echo "bash"
}
install() {
# Include the Axelera driver and RPi5 I/O drivers
inst_mods axdevice rp1_uart rp1_pci
# Include the specific DTBOs in the initramfs
inst "/boot/overlays/exaviz-cruiser.dtbo" "/boot/overlays/exaviz-cruiser.dtbo"
inst "/boot/overlays/axelera-metis.dtbo" "/boot/overlays/axelera-metis.dtbo"
}
install -Dm755 module-setup.sh /usr/lib/dracut/modules.d/95rpi-hardware/module-setup.sh
dracut --force --regenerate-all
99-axelera.rules dracut udev rules
These rules run inside the initramfs and create the /dev/axelera0 symlink for the Metis. The Hailo-8 rule is included for compatibility with other accelerators that use the same repository.
# Axelera M.2 (Pre-release & Retail)
# Uses the 'accel' subsystem — new standard for AI chips
SUBSYSTEM=="accel", ATTRS{vendor}=="0x1e81", SYMLINK+="axelera0", \
TAG+="systemd", MODE="0660", GROUP="render"
# Hailo-8
SUBSYSTEM=="hailo_pci", ATTRS{vendor}=="1e60", SYMLINK+="hailo0", \
TAG+="systemd", MODE="0660", GROUP="render"
The render group is used here for initramfs compatibility. After the root filesystem is mounted, the axelera group takes over via the rule in /etc/udev/rules.d/99-axelera-metis.rules.
Installing the metis-dkms package (Arch Linux)
The metis-dkms PKGBUILD builds and installs the Axelera Metis PCIe kernel driver via DKMS. The driver source is fetched from the axelera-ai-hub/axelera-driver repository.
pkgname=metis-dkms
pkgver=1.5.0
pkgrel=1
pkgdesc="Axelera Metis PCIe driver (DKMS)"
arch=('x86_64' 'aarch64')
url="https://github.com/axelera-ai-hub/axelera-driver"
license=('GPL2')
depends=('dkms')
makedepends=('linux-headers')
source=("$pkgname-$pkgver::https://github.com/axelera-ai-hub/axelera-driver/archive/refs/tags/v$pkgver.tar.gz")
sha256sums=('SKIP')
build() {
cd axelera-driver-$pkgver
}
package() {
cd axelera-driver-$pkgver
install -d "$pkgdir/usr/src/metis-$pkgver"
cp -r . "$pkgdir/usr/src/metis-$pkgver"
install -Dm644 dkms.conf \
"$pkgdir/usr/src/metis-$pkgver/dkms.conf"
}
Clone or copy the PKGBUILD
git clone https://github.com/axelera-ai-hub/axelera-driver
cp PKGBUILD axelera-driver/
cd axelera-driver
Install the package
pacman -U metis-dkms-1.5.0-1-aarch64.pkg.tar.zst
Verify the module loaded
lsmod | grep axdevice
dmesg | grep -i axelera
sha256sums=('SKIP') is set in the PKGBUILD. Before deploying to production, pin the checksum to a known-good release tarball to prevent supply-chain substitution.
