Interface will not rename under systemd

networkingsystemdubuntu-16.04

I'm trying to rename a network interface on an Ubuntu 16.04 VPS, but am unable to do so. Systemd names my primary network interface enp0s3. I want to rename this interface to eth0.

According to the systemd.link documentation I created a file called /etc/systemd/network/10-eth0.link with the following content:

[Match]
MACAddress=08:00:27:f7:57:e5

[Link]
Name=eth0

The MAC address matches the one given in the ip a output for the interface. I also renamed the enp0s3 entries to eth0 in the /etc/network/interfaces file. Although, when I reboot the machine, the interface is still named enp0s3.

The following entries in the dmesg output are interesting to me:

e1000 0000:00:03.0 eth0: (PCI:33MHz:32-bit) 08:00:27:f7:57:e5
e1000 0000:00:03.0 eth0: Intel(R) PRO/1000 Network Connection
e1000 0000:00:03.0 enp0s3: renamed from eth0

So apparently, it starts out as eth0, but is then renamed back to enp0s3 again. I am not sure why?

When I try to debug the link file, I get the following output:

$ sudo udevadm test-builtin net_setup_link /etc/systemd/network/10-eth0.link
calling: test-builtin
=== trie on-disk ===
tool version:          229
file size:         6841778 bytes
header size             80 bytes
strings            1755242 bytes
nodes              5086456 bytes
Load module index
timestamp of 'etc/systemd/network' changed
Parsed configuration file /lib/systemd/network/99-default.link
Parsed configuration file /etc/systemd/network/10-eth0.link
Created link configuration context.
unable to open device '/sys/etc/systemd/network/10-eth0.link'

Unload module index
Unloaded link configuration context.

The line about it being unable to open the device seems odd. I'm not sure why it's trying that, there is no etc directory under /sys at all, should I create it?

Any insights into why my interface name doesn't stick is very welcome.

Best Answer

According to https://www.freedesktop.org/software/systemd/man/systemd.link.html, the default naming policy is:

#  /usr/lib/systemd/network/99-default.link
[Link]
NamePolicy=kernel database onboard slot path
MACAddressPolicy=persistent

So I suspect you might want to add the following line to your eth0.link:

NamePolicy=mac

I haven't tested this, so I am not certain, but I suspect the issue is that you Match on MAC, but there is no naming policy to make that stick.

Each of the policies may fail, and the first successful one is used. The name is not set directly, but is exported to udev as the property "ID_NET_NAME", which is, by default, used by a udev rule to set "NAME". If the name has already been set by userspace, no renaming is performed

It is just a guess though.

You should also be able to just disable the default.link, at least per https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/

On some openSUSE systems I run, I had a similar issue, which (in addition to having had to use the 99-default.link 'trick') was resolved by creating two files under /etc/udev/rules.d (see https://unix.stackexchange.com/questions/118272/80-net-setup-link-no-longer-functions-when-i-downgraded-systemd, https://wiki.archlinux.org/index.php/Network_configuration#Device_names and https://wiki.gentoo.org/wiki/Udev/Upgrade_Guide):

sudo touch /etc/udev/rules.d/80-net-setup-link.rules (or just make sure an empty file of that name is in that location)

AND

I created /etc/udev/rules.d/10-persistent-network.rules:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="eth*", ATTR{tx_queue_len}="1000"

In your case, you could actually use that file to set the name you want:

ACTION=="add", SUBSYSTEM=="net",ATTR{address}=="08:00:27:f7:57:e5",NAME="eth0"
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