Configuration of mdev (minimalistic Device Manager from Busybox) for a server system, where udev is really not necessary.

howto-gentoo.md

How to replace udev with mdev on Gentoo

1. Ensure that you haven’t installed any package that needs udev:

   equery depends udev
   

2. Disable USE udev in /etc/portage/make.conf.

3. Enable USE mdev for busybox (and disable pam, it supposedly doesn’t work with static well):

   echo 'sys-apps/busybox static mdev -pam' >> /etc/portage/package.use
   

4. Reemerge busybox:

   emerge -av busybox
   

5. Copy configuration /etc/mdev.conf (see mdev.conf).

6. Add mdev to runlevel sysinit:

   rc-update add mdev sysinit
   

7. Remove udev* init scripts from runlevels:

   rc-update del udev sysinit
   rc-update del udev-mount sysinit
   rc-update del udev-postmount
   

8. Finally unmerge udev:

   emerge --unmerge -a sys-fs/udev virtual/udev sys-fs/udev-init-scripts
   

9. Mask udev:

   echo -e "# we're using mdev from busybox instead\nsys-fs/udev" >> /etc/portage/package.mask/udev
   

10. Reboot and hope that everything will be okay. :)

Rename network interfaces

If you want to rename network interfaces (e.g. lan1 instead of eth1), then create file /etc/mactab with pair of an interface name and a Ethernet MAC address on each line. For example:

# Allow busybox's "nameif" to rename downed interfaces on the basis of their
# MAC addresses.
wan0  12:34:56:78:9a:bc
lan0  12:34:56:78:9a:de

This file is read by busybox’s nameif during mdev initialization (see line 55 in mdev.conf). Read man nameif for more information.

Note: Desired interface names should be different than eth[0-9] (nameif can’t swap names).

 

Thanks to Stuart for his article https://blog.stuart.shelton.me/archives/891.

mdev.conf

#
# mdev.conf for a server system
#

# Provide user, group, and mode information for devices.  If a regex matches
# the device name provided by sysfs, use the appropriate user:group and mode
# instead of the default 0:0 660.
#
# Syntax:
# [-]devicename_regex user:group mode [=path]|[>path]|[!] [@|$|*cmd args...]
# [-]$ENVVAR=regex    user:group mode [=path]|[>path]|[!] [@|$|*cmd args...]
# [-]@maj,min[-min2]  user:group mode [=path]|[>path]|[!] [@|$|*cmd args...]
#
# [-]: do not stop on this match, continue reading mdev.conf
# =: move, >: move and create a symlink
# !: do not create device node
# @|$|*: run cmd if $ACTION=remove, @cmd if $ACTION=add, *cmd in all cases

# support module loading on hotplug
$MODALIAS=.*    root:root 660 @/sbin/modprobe "$MODALIAS"

# null may already exist; therefore ownership has to be changed with command
null            root:root 666 @/bin/chmod 666 $MDEV
zero            root:root 666
full            root:root 666
random          root:root 444
urandom         root:root 444
grsec           root:root 622

kmem            root:kmem 640
kmsg            root:root 640
mem             root:kmem 640
# console may already exist; therefore ownership has to be changed with command
console         root:tty 600 @/bin/chmod 600 $MDEV
ptmx            root:tty 666
pty.*           root:tty 660

-cpu.*          root:root 755 @/bin/mkdir -pm 755 cpu ; /bin/rm $MDEV
cpu([0-9]+)     root:root 444 =cpu/%1/cpuid

# terminal devices
tty             root:tty 666
tty[0-9]+       root:tty 660
vcsa?[0-9]*     root:tty 660
ttyS[0-9]+      root:uucp 660

# block devices
ram([0-9]+)     root:disk 660 >rd/%1
loop([0-9]+)    root:disk 660 >loop/%1
sd[a-z].*       root:disk 660 */lib/mdev/usbdisk_link
vd[a-z][0-9]*   root:disk 660
md[0-9]+        root:disk 660 @/bin/mkdir -pm 755 md ; /bin/ln -sf ../$MDEV md/${MDEV/md}

# net devices
-net/.*         root:root 600 @/sbin/nameif -s
net/tun[0-9]*   root:root 600
net/tap[0-9]*   root:root 600

# usb printers
usb/lp[0-9]*    root:lp 660

# misc stuff
rtc0            root:root 600 @/bin/ln -sf $MDEV rtc
fuse            root:root 666
#kvm             root:kvm  660

# input stuff
event[0-9]+     root:root 640 =input/
mice            root:root 640 =input/
mouse[0-9]      root:root 640 =input/
ts[0-9]         root:root 600 =input/