105

When I run ifconfig -a, I only get lo and enp0s10 interfaces, not the classical eth0

What does enp0s10 mean? Why is there no eth0?

3
  • 9
    ifconfig is deprecated. Think about moving to ip from iproute2 soon. – solsTiCe Jun 13 '15 at 8:21
  • 1
    As the answer says it's a change in systemd. To get your eth0 back use the kernel option net.ifnames=0 biosdevname=0 (see this thread). Using ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rule in below answer didn't work in Debian 10 (Buster) – MrCalvin Jun 2 '19 at 10:22
  • @MrCalvin : the ln -s ... should be updated, see below – serv-inc Dec 16 '20 at 10:44
86

That's a change in how now udevd assigns names to ethernet devices. Now your devices use the "Predictable Interface Names", which are based on (and quoting the sources):

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

The why's this changed is documented in the systemd freedesktop.org page, along with the method to disable this:

ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rules

or if you use older versions:

ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules
2
  • 12
    Following the freedesktop,org link, the main point is: The classic naming scheme for network interfaces applied by the kernel is to simply assign names beginning with "eth" to all interfaces as they are probed by the drivers. As the driver probing is generally not predictable for modern technology this means that as soon as multiple network interfaces are available the assignment of the names is generally not fixed anymore and it might very well happen that "eth0" on one boot ends up being "eth1" on the next. This can have serious security implications... – lepe Oct 17 '16 at 2:43
  • This also applies to docker images. So trying to setup a network bridge between 2 docker networks caused problems 2 years ago because the network ports could be reversed on next boot. an impossible situation for a bridge device. – U.V. Dec 16 '20 at 12:01
145

Answer on "What does enp0s10 means?" question:

enp0s10:
| | |
v | |
en| |   --> ethernet
  v |
  p0|   --> bus number (0)
    v
    s10 --> slot number (10)

Source: udev-builtin-net_id.c on GitHub

3
  • 13
    Came looking for this. – ffledgling Mar 7 '17 at 8:38
  • 7
    Since there is no ...fN part at the end of the NIC name, we can deduce that the function number is 0. After translating the numbers to hexadecimal (10 = "a" in hex), we know that enp0s10 means PCI device ID 00:0a.0. – telcoM Apr 13 '19 at 6:13
  • There’s also freedesktop.org/software/systemd/man/… – user3840170 Dec 8 '20 at 20:21
22

As mentioned above, enp0s10 refers to ethernet (en), prefix 0 (p0), slot 10 (s10). The bus number, device number, and function number are pulled from Bus Device Function (BDF) for PCI devices to create the prefix, slot, and function portions of the Predictable Network Interface Name.

If the function is 0, the f0 portion is omitted. I changed the prefix from p0 to p4, and the function from f0 to f1, for clarity in this example.

Expanding on the answer posted by 'DIG mbl':

enp4s10f1                        pci 0000:04:0a.1
| | |  |                                |  |  | |
| | |  |                   domain <- 0000  |  | |
| | |  |                                   |  | |
en| |  |  --> ethernet                     |  | |
  | |  |                                   |  | |
  p4|  |  --> prefix/bus number (4)   <-- 04  | |
    |  |                                      | |
    s10|  --> slot/device number (10) <--    10 |
       |                                        |
       f1 --> function number (1)     <--       1

https://wiki.xen.org/wiki/Bus:Device.Function_(BDF)_Notation https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames

I came across a device with a u7 at the end, for USB port. Some of the different label possibilities are included in this documentation: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/sec-understanding_the_predictable_network_interface_device_names

3
  • I'm a little confused. You said "Since function is 0, the f0 portion is omitted", but why did you change prefix in order not to omit f0? – ebk May 13 '20 at 11:28
  • 1
    I'm trying to illustrate what each section of the Predictable Network Interface Name would be. I changed my example, changing f0 to f1. I changed the prefix to make the illustration easier to follow; the change had nothing to do with the function portion. Thanks – mhck May 13 '20 at 12:20
  • I got it now :) Thanks for your great answer. – ebk May 13 '20 at 13:03
0

To quote the full text on disabling linked by @Braiam:

I don't like this, how do I disable this?

You basically have three options:

  1. You disable the assignment of fixed names, so that the unpredictable kernel names are used again. For this, simply mask udev's .link file for the default policy: ln -s /dev/null /etc/systemd/network/99-default.link
  2. You create your own manual naming scheme, for example by naming your interfaces "internet0", "dmz0" or "lan0". For that create your own .link files in /etc/systemd/network/, that choose an explicit name or a better naming scheme for one, some, or all of your interfaces. See systemd.link(5) for more information.
  3. You pass the net.ifnames=0 on the kernel command line

TL;DR: it has been renamed to 99-default.link

-1

You can use

net.ifnames=0

in kernel command line arguments and your interface name will be called eth0 again.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.