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8.10. Troubleshooting Network Device Naming

Predictable interface names will be assigned for each interface, if applicable, as per the procedure described in Section 8.2, “Understanding the Device Renaming Procedure”. To view the list of possible names udev will use, issue a command in the following form as root:
~]# udevadm info /sys/class/net/ifname | grep ID_NET_NAME
where ifname is one of the interfaces listed by the following command:
~]$ ls /sys/class/net/
One of the possible names will be applied by udev according to the rules as described in Section 8.2, “Understanding the Device Renaming Procedure”, and summarized here:
  • /usr/lib/udev/rules.d/60-net.rules - from initscripts,
  • /usr/lib/udev/rules.d/71-biosdevname.rules - from biosdevname,
  • /usr/lib/udev/rules.d/80-net-name-slot.rules - from systemd
From the above list of rule files it can be seen that if interface naming is done via initscripts or biosdevname it always takes precedence over udev native naming. However if initscripts renaming is not taking place and biosdevname is disabled, then to alter the interface names copy the 80-net-name-slot.rules from /usr/ to /etc/ and edit the file appropriately. In other words, comment out or arrange schemes to be used in a certain order.
Example 8.1. Some interfaces have names from the kernel namespace (eth[0,1,2...]) while others are successfully renamed by udev
Mixed up schemes most likely means that either for some hardware there is no usable information provided by the kernel to udev, thus it could not figure out any names, or the information provided to udev is not suitable, for example non-unique device IDs. The latter is more common and the solution is to use a custom naming scheme in ifcfg files or alter which udev scheme is in use by editing 80-net-name-slot.rules.

Example 8.2. In /var/log/messages or the systemd journal, renaming is seen to be done twice for each interface
Systems with the naming scheme encoded in ifcfg files but which do not have a regenerated initrd image are likely to encounter this issue. The interface name is initially assigned (via biosdevname or udev or dracut parameters on the kernel command line) during early-boot while still in initrd. Then after switching to real rootfs, renaming is done a second time and a new interface name is determined by the /usr/lib/udev/rename_device binary spawned by udev because of processing 60-net.rules. You can safely ignore such messages.

Example 8.3. Using naming scheme in ifcfg files with ethX names does not work
Use of interface names from kernel namespace is discouraged. To get predictable and stable interface names please use some other prefix than "eth".