Udev/Upgrade Guide

Warning
Be careful when upgrading udev! Consider the changes listed below; ignoring them can, and probably will, break the system!

Udev is a central system component and may require extra care on upgrades.

Example interface IDs

The default naming precedence rules are these:

Names incorporating Firmware/BIOS provided index numbers for on-board devices (ID_NET_NAME_ONBOARD, example: eno1)
Names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (ID_NET_NAME_SLOT, example: ens1)
Names incorporating physical/geographical location of the connector of the hardware (ID_NET_NAME_PATH, example: enp2s0)
Names incorporating the interfaces's MAC address (ID_NET_NAME_MAC, example: enx78e7d1ea46da)
Classic, unpredictable kernel-native ethX naming (example: eth0)

(Rule 4 is disabled by default.) So, if output is like this:

user $udevadm test-builtin net_id /sys/class/net/eth0 2> /dev/null

ID_NET_NAME_MAC=enxd4a8xxxxxxxx
ID_NET_NAME_ONBOARD=eno1
ID_NET_NAME_PATH=enp1s0f1

The interface will be named eno1, because ID_NET_NAME_ONBOARD takes precedence over ID_NET_NAME_PATH.

Things to think of when upgrading

/etc/conf.d/net
Renaming init scripts
Replacing init scripts in runlevels (via rc-update)
iptables configuration
vnstat configuration
samba configuration

A quick way to get a list of files that will need to be updated can be found using the following:

user $grep -r 'eth0' /etc/* | grep -v '#'

Fixing network interfaces

This section provides examples on how to fix network-interfaces if they do not work anymore (or before they stop working before the new udev package has been switched to). It is only applicable to simple setups, like one ethernet and one wifi interface. For more complicated setup (like more ethernet adapters) most users should already know what to do.

Renaming init scripts

If still running the old udev and are ready to enable the new one, then execute:

user $udevadm test-builtin net_id /sys/class/net/eth0 2> /dev/null

ID_NET_NAME_MAC=enxd4a8xxxxxxxx
ID_NET_NAME_PATH=enp1s0f1

Take the ID_NET_NAME_PATH-item (here enp1s0f1) and execute

user $ln -s net.lo /etc/init.d/net.enp1s0f1

Do the same for any wifi-interfaces.

When already running the new udev and the network is down, execute:

user $ls -la /sys/class/net

total 0
drwxr-xr-x  2 root root 0 Apr  2 19:42 ./
drwxr-xr-x 49 root root 0 Apr  2 19:42 ../
lrwxrwxrwx  1 root root 0 Apr  2 19:42 enp1s0f1 -> ../../devices/pci0000:00/0000:00:1c.1/0000:02:00.0/net/enp1s0f1/
lrwxrwxrwx  1 root root 0 Apr  2 19:42 lo -> ../../devices/virtual/net/lo/
lrwxrwxrwx  1 root root 0 Apr  2 19:42 sit0 -> ../../devices/virtual/net/sit0/

Look which link points to a pci-device (here enp1s0f1) and execute:

user $ln -s net.lo /etc/init.d/net.enp1s0f1

When wifi-interfaces exist do not forget include these interfaces as well.

Replacing init scripts in runlevels (via rc-update)

user $

rc-update delete net.eth0 default

user $

rc-update add net.enp1s0f1 default

If necessary do the same for any wifi-interfaces.

Instruction to upgrade to specific versions

Note
This section currently (2021) contains only instructions for updates that were required years ago, and should no longer be needed. If a more involved upgrade (that requires instructions) happens again, it should be accompanied by a corresponding news item (that must be read and followed), and may also get a new entry here.

udev 171 to 204

The following special attention is required:

CONFIG_DEVTMPFS=y must be set in the kernel. To do this Linux kernel 2.6.32+ is needed.

If there is a /dev line in /etc/fstab, it must have the devtmpfs filesystem type or it will conflict with the above options.

Remove udev-postmount from any runlevels, it is not necessary. Exception: Note that sys-fs/eudev still has the udev-postmount init script in use with USE="rule-generator"

When using /etc/udev/rules.d/70-persistent-net.rules, read Predictable Network Interface Names,

otherwise delete it together with /etc/udev/rules.d/70-persistent-cd.rules as both are from the now deleted rule_generator that does not exist anymore.

The new Predictable Network Interface Names will be used by default, unless the kernel commandline contains the net.ifnames=0 parameter. (If the method of masking out the /etc/udev/rules.d/80-net-name-slot.rules file was used in the past be aware it will not work in v209 and newer releases.)

When using Linux 3.8 or higher it should be possible to disable USE="firmware-loader" and let the kernel do the loading instead. However, USE="firmware-loader" can be used on newer kernels too.

sys-apps/biosdevname is no longer necessary if the Predictable Network Interface Names are being used.

Any file that has not been personally created or edited in /etc/udev/rules.d should be backed up and removed since it is likely a relic from old an udev installation.

For more details, read the full news article /usr/portage/metadata/news/2013-03-29-udev-upgrade/2013-03-29-udev-upgrade.en.txt and the post install output of emerging udev.

udev 204 to 208

The following special attention is required:

Since this version, kernel with accept4() function support is mandatory. It is supported for amd64, ia64, mips, sparc and x86 in 2.6.32.61. All others, like ARM, will need a newer kernel like 3.0 for the function.
It is no longer the job of the /dev manager, like udev, to create /dev nodes for static kernel modules such as /dev/fuse or /dev/snd/seq. Instead they are now created by the kmod-static-nodes init script which is part of sys-apps/kmod since version 15. Make sure the init script has been added to the "sysinit" runlevel.

udev 208 to 216

The following special attention is required:

Since this version, kernel settings CONFIG_FHANDLE=y and CONFIG_NET=y are mandatory. Kernel setting CONFIG_DMIID=y is recommended for amd64/ia64/x86, for example, keyboard rules.
File /lib/udev/rules.d/80-net-name-slot.rules was replaced with /lib/udev/rules.d/80-net-setup-link.rules. If currently using an empty (or single-comment) /etc/udev/rules.d/80-net-name-slot.rules to disable predictable network interface names, the 80-net-setup-link.rules should now be used. For example:

root #cd /etc/udev/rules.d/ && ln 80-net-name-slot.rules 80-net-setup-link.rules

This keeps the override both pre- and post-upgrade; then run:

root #rm /etc/udev/rules.d/80-net-name-slot.rules

once the upgrade has been made. The hardlink can be made, in order to protect against not noticing the upgrade in a busy or non-professional situation.

However, 80-net-setup-link.rules is only a trigger for the actual configuration file 99-default.link at /lib/systemd/network/ which can be overrided at /etc/systemd/network/
The most reliable way of disabling the new network interface scheme is still the kernel bootline parameter: net.ifnames=0

udev 216 to 217

The following special attention is required:

Since this version, kernel setting CONFIG_FW_LOADER_USER_HELPER should be set to =n, because the userspace firmware loader has been removed. Upgrade the kernel at least to version 3.7 for the kernel firmware loader.
If CONFIG_FW_LOADER_USER_HELPER cannot be disabled, try to disable CONFIG_DELL_RBU, it will select CONFIG_FW_LOADER_USER_HELPER automatically in Linux kernel 3.18.x.