Renaming a Network Interface in Ubuntu 18.04 on IBM Cloud

For a project I'm working on, I have a requirement to spin up a VM in IBM Cloud, running Ubuntu 18.04 and with a very specific requirement of having an interface named eth0 (I will be running EVE-NG on this VM).  The VM I am working with has a default interface name of ens3, which I want to change to eth0.

There are a few steps involved to make this change:

1. Get the MAC address for the interface
2. Add a rule in 70-persistent-net.rules
3. Rename the interface in /etc/netplan
4. Persist the interface name change across reboots
5. Switch from Predictable Network Interface Names to Persistent Names scheme
6. Reboot the VM

Step 1: Get the Interface MAC Address

Issue the ifconfig command (shown in the snippet below) and locate the ens3 interface from the output.  In this example, the MAC address is 02:01:fb:33:37:bb

root@eve-ng:~# ifconfig
ens3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.240.69.254  netmask 255.255.252.0  broadcast 10.240.71.255
        inet6 fe80::1:fbff:fe33:37bb  prefixlen 64  scopeid 0x20<link>
        ether 02:01:fb:33:37:bb  txqueuelen 1000  (Ethernet)
        RX packets 9045  bytes 122655341 (122.6 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 6315  bytes 915074 (915.0 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Step 2: Add a Rule in "70-persistent-net.rules"

Device management in Linux is handled by the udev daemon.  The udev deamon uses MAC addresses to assign persistent names to interfaces.  With that in mind, the next step is to cd to the /etc/udev/rules.d directory and check if a file called 70-persistent-net.rules exists.  If it doesn't, then create the file and add the following to it, being sure to replace <INTERFACE_MAC_ADDRESS> with the MAC address of your interface (e.g. 02:01:fb:33:37:bb), and <NEW_INTERFACE_NAME> with the new interface name (e.g. eth0):

SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}==“<INTERFACE_MAC_ADDRESS>”, NAME=“<NEW_INTERFACE_NAME>”

So, for my particular use case, I added the following entry to my 70-persistent-net.rules file:

SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="02:01:fb:33:37:bb", NAME=“eth0”

Step 3: Rename the Interface in "/etc/netplan"

The next step is to cd to /etc/netplan and see what file is there.  In my case, I have a file in that directory called 50-cloud-init.yaml.  The contents of this file are pasted below:

# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        ens3:
            dhcp4: true
            match:
                macaddress: 02:01:fb:33:37:bb
            set-name: ens3
    version: 2

Edit this file and replace any instances of the original interface name (e.g. ens3) with the new desired interface name (e.g. eth0).  After making these changes, my 50-cloud-init.yaml file looked like this:

# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        # original value: ens3
        eth0:
            dhcp4: true
            match:
                macaddress: 02:01:fb:33:37:bb
            # original value: ens3
            set-name: eth0
    version: 2

Step 4: Persist the Interface Name Change Across Reboots

In Step 3 above, note the comments at the very top of the 50-cloud-init.yaml file:

# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}

On this IBM Cloud VM, the changes made to the 50-cloud-init.yaml file will not persist across reboots.  Following the instructions in the comments, create a new file in /etc/cloud/cloud.cfg.d called 99-disable-network-config.cfg and add the following single line:

network: {config: disabled}

Step 5: Switch From "Predictable Network Interface Names" to "Persistent Names" Scheme

Beginning with version 197, systemd/udev automatically assigns predictable names for all network interfaces (e.g. "ens1"), a scheme referred to as "Predictable Network Interface Names".  Newer Linux distributions use this scheme, which allows for interfaces to be named in a reproducible way.  This is in contrast to the traditional "Persistent Names" scheme, which assigned interface names (beginning with "eth0", "eth1", etc.) in the order in which the interfaces were probed by the drivers.  As a result, the "Persistent Names" scheme does not assign interface names in a reproducible way because the order in which driver probing occurs is not predictable.  This was the reason for moving to the "Predictable Network Interface Names" scheme.

Edit the /etc/default/grub file and replace the line GRUB_CMDLINE_LINUX="" with the following:

GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"

After this, be sure to apply the settings by issuing the update-grub command.

Step 6: Reboot the VM

Finally, reboot the VM.  When the VM comes back, verify that the changes were applied by issuing the ifconfig command and verifying that the interface has been renamed to eth0:

root@eve-ng:~# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.240.69.254  netmask 255.255.252.0  broadcast 10.240.71.255
        inet6 fe80::1:fbff:fe33:37bb  prefixlen 64  scopeid 0x20<link>
        ether 02:01:fb:33:37:bb  txqueuelen 1000  (Ethernet)
        RX packets 63  bytes 9849 (9.8 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 59  bytes 9647 (9.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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