So I found a PCI Wi-Fi 5 device, and I decided to put it in my diskless system that boots Arch Linux from NFS, and turn it into a Wi-Fi access point, hoping to improve reception in my living room. Should be easy, right?

We're gonna use hostapd for this. The problem is, hostapd will want to bridge the Ethernet connection to the Wi-Fi device, which means temporarily shutting down Ethernet while creating a bridged connection, a thing the NFS client won't like at all and will throw the whole system into a nasty I/O deadlock.

Solution: creating that bridge in the initramfs, ideally before the root is mounted and at the same time the system brings up the networking.

/usr/bin/bridge-add

#!/bin/sh
 
ip link add name $2 type bridge
ip link set dev $2 up
ip link set $1 up
ip link set $1 master $2

/usr/lib/udev/rules.d/70-persistent-net.rules

SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="<wired MAC address>", ATTR{dev_id}=="0x0", ATTR{type}=="1", NAME="eno1", RUN+="/usr/bin/bridge-add eno1 br0"

Add the correct modules and files to your initramfs generator config:

/etc/mkinitcpio.conf

MODULES=(nfsv4 bridge)
BINARIES=(/usr/bin/mount.nfs4 /usr/bin/bridge-add)
FILES=(/usr/lib/udev/rules.d/70-persistent-net.rules)

Then you can replace eth0 with br0 in your kernel command line on your bootloader:

ip=:::::br0:dhcp nfsroot=192.168.1.10:/arch

Run mkinitcpio, reboot, and hopefully you have a usable system again, but now with a br0 device.

Now you can continue with the instructions on Software access point.

5 GHz networking?