Disabling Consistent Network Device Naming in RHEL and CentOS

RedHat Sep 26, 2017

Consistent Network Device Naming was concieved to mitigate issues that would arise on machines where new network interfaces were installed, thus possibly changing the boot order, and their corresponding network device name [1]. Whilst this is incredibly useful in many scenarios, there remains certain situations where this is undesirable, and can cause many issues. Red Hat introduced this in RHEL7 and CentOS7[2], but thankfully this is relatively easy, albeit slightly hazardous to fix.



The Fix

You need to edit the kernel boot arguments, to do so, open the grub.cfg file.

vi /etc/default/grub



This should appear similar to the following:

GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos_mysystem/root 
rd.lvm.lv=centos_mysystem/swap rhgb quiet"
GRUB_DISABLE_RECOVERY="true"



Two arguments, biosdevname=0 and net.ifnames=0, need to be added to the sixth line beginning with “GRUB_CMDLINE_LINX”, to make it appear like the following:

GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos_genserver01/root 
rd.lvm.lv=centos_genserver01/swap rhgb quiet biosdevname=0 net.ifnames=0"



After this is done, exit your editor and make the grub2 config, and reboot:

grub2-mkconfig -o /boot/grub2/grub.cfg
reboot



Run ifconfig (net-tools is required) and confirm that the ethX naming scheme is running:

ifconfig



Whilst we are almost done, we still need to edit the network scripts:

cd /etc/syconfig/network-scripts
ls -l



There are many files in this folder, but as you will notice, there is no ifcfg-eth0, only ifcfg-enp0s3 (or similar). This file needs to be removed, but it is good to place it with the temopoary files in case it is required for reference or an error arises.

mv ifcfg-enp0s3 /tmp/



Now a new file needs to be created.

vi ifcfg-eth0



The contents of this file will vary on your requirements, but it will most probably be nearly identical to your ifcfg-enp0s3 file, with a few changes.

TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="enp0s3"
UUID="c4f7a4f0-3282-4aae-8a67-6282259f5467"
DEVICE="enp0s3"
ONBOOT="yes"



Three lines need to be changed, name and device must change to “eth0”, and the UUID needs to be changed. The UUID of the new device can be found by running the following:

uuidgen eth0



References

[1] M. Domsch, “PATCH: Network Device Naming mechanism and policy [LWN.net]”, 2009. [Online]. Available: https://lwn.net/Articles/356900/. [Accessed: 26- Sep- 2017]

[2] “Chapter 8. Consistent Network Device Naming - Red Hat Customer Portal”, Access.redhat.com, 2017. [Online]. Available: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/ch-consistent_network_device_naming. [Accessed: 26- Sep- 2017]