mdevd

Check alpine’s patches
Start mdevd with -O4; this will make the daemon rebroadcast kernel uevents to libudev-zero
Readiness -D only works when mdevd is being called by s6 and not manually in an initramfs
A summary of what mdevd-coldplug and udevadm trigger do:

for i in $(find /sys -name uevent); do ( echo change > $i ) ; done

There is no test suite
yash does not specify PATH in initramfs which causes mdevd to not find its commands; this problem seems to not exist when using dash
mdev.conf syntax:

<device regex> <uid>:<gid> <permissions> [=path|>path|!] [@|$|*<command>]

- =path moves to path
- >path symlinks device to path
- ! prevents device from being created

- @ Run after creating the device.
- $ Run before removing the device.
- * Run both after creating and before removing the device.

The command is executed via the system() function (which means you’re giving a command to the shell), so make sure you have a shell installed at /bin/sh. You should also keep in mind that the kernel executes hotplug helpers with stdin, stdout, and stderr connected to /dev/null.
Use libudev helper in mdev.conf
Does mdevd work with udev directories and rules or should we delete them?

mdev.conf

mdevd parses mdev.conf when a new device event occurs
/dev/audio and /dev/dsp have been replaced with newer drivers and naming conventions
/dev/core has been deprecated
/dev/dsp and /dev/adsp have been deprecated as modern systems don’t use OSS
/dev/fd0 has been deprecated
/dev/grsec has been deprecated since 4.14
/dev/hd{a,b,c} have been deprecated
/dev/hwrng has replaced /dev/hwrandom and /dev/hw_random
/dev/mixer and /dev/sequencer have been deprecated as modern systems don’t use OSS
/dev/psaux has been deprecated
/dev/pty has been deprecated since 2.6.4 (https://man7.org/linux/man-pages/man7/pty.7.html)
/dev/snd has replaced /dev/sound
/dev/sr0 has replaced /dev/cdrom
/dev/sda has replaced /dev/cciss and /dev/ida

mdevd

mdev.conf

References