Context for newbies: Linux refers to network adapters (wifi cards, ethernet cards, etc.) by so called “interfaces”. For the longest time, the interface names were assigned based on the type of device and the order in which the system discovered it. So, eth0, eth1, wlan0, and wwan0 are all possible interface names. This, however, can be an issue: “the order in which the system discovered it” is not deterministic, which means hardware can switch interface names across reboots. This can be a real issue for things like servers that rely on interface names staying the same.
The solution to this issue is to assign custom names based on MAC address. The MAC address is hardcoded into the network adaptor, and will not change. (There are other ways to do this as well, such as setting udev rules).
Redhat, however, found this solution too simple and instead devised their own scheme for assigning network interface names. It fails at solving the problem it was created to solve while making it much harder to type and remember interface names.
To disable predictable interface naming and switch back to the old scheme, add net.ifnames=0 and biosdevname=0 to your boot paramets.
The template for this meme is called “stop doing math”.
To disable predictable interface naming and switch back to the old scheme, add
net.ifnames=0andbiosdevname=0to your boot paramets.What is the old scheme? This?
The solution to this issue is to assign custom names based on MAC address. The MAC address is hardcoded into the network adaptor, and will not change. (There are other ways to do this as well, such as setting udev rules).
Does that mean that until you name something it’s unusable?
No, the “old scheme” is the one that assigns
wlan0,wlan1,eth0,eth1, and so on by default. I would say these names are pretty usable.The part you quoted is what you need to do if you specifically need to be sure that a specific card gets a specifc name 100% of the time. You don’t have to bother with it unless you have a reason to.
eth0? No no, we need wlps0n1pn2d4es6vsd9c69420
I had to change mine to mac address naming on my proxmox server after the second time the name changed due to a GPU or SSD being added. It was kind of like, so what, if an SSD dies suddenly or I have some issue with a device you are going to rename my fucking nic card again while I am trying to troubleshoot? Absolutely deranged.
Also, make sure your password contains L’s, 1’s, 0’s and O’s in a font deliberately chosen to make them hard to tell apart.
I laughed so hard. Then I cried remembering good old days of
eth0.Holy shit. I must be really old.
I laughed but now that I know it I’m going to change the udev rules back to eth0.
Good lord, this is a top tier meme!
Thanks, glad you like it! I spent quite some time re-making the template from scratch in inkscape, because the original meme din’t have enough space for the text
I often do the same for my memes. I like them high quality
Heck yeah, vectorised libre memes ftw!
As someone who worked on a pre-systemd linux system with multiple NICs and needed them all configured automatically from an OS image based on where it was in the rack, I can’t stress enough how good deterministic interface names are.
Booting up a system and each time having different names for each NIC was a nightmare.
Frankly 90+% of what systemd has done is tremendously positive and makes linux a better operating system to use, both for sys admins and end users.
Couldn’t they be configured to always set each interface to a particular name? I’d think that would be the better solution anyway…
Thanks for this post. I’ve been working with Interfaces on Red Hat nodes this week and I’ve already wondered what the hell is going on there.
“the order in which the system discovered it” is not deterministic
This is the same problem they had with hard drive names and it seems to have been solved in a sensible way, i.e. /dev/sda still points to the first disk detected by the system, but you can look look in /dev/disk/by-path (or by-uuid, etc) to see the physical address of the devices on the system and what they are symlinked back to, and set your fstab or mdadm arrays to be configured based on those unique identifiers instead.
So, I guess what I’d like to know is why hasn’t this been solved the same way? When you boot up they should present every hard wired Ethernet port as
ethX, and the hardware address interface should be present as well but aliased back to theeth. Then you can build the your network configs based on either one.Shouldn’t be that hard right?
And at least in some distributions, they do exactly that, a number of aliases for the same interface. And you can add your own.
As a data center engineer of 10+ years, I struggled to understand this at first. In my world, the hardware does a POST before the OS boots and has an inventory of what hardware components are available, so it shouldn’t matter in what order they are discovered, since the interface names should make a correlation between the interface and the pcie slot that NIC exists in.
Where the water gets muddled is in virtualized servers. The NICs no longer have a correlation to a specific hardware component, and you may need to configure different interfaces in the virtualized OS for different networks. I think in trying to create a methodology that is agnostic to bare metal/virtualized OSs, it was decided that the naming convention should be uniform.
Probably seems like bloat to the average admin who is unconcerned with whether these NICs are physical or virtual, they just want to configure their server.
Cries in
nvme1n1p6, which is my current OS partition.Taking a sip of Rum and chuckles at the look on the name of my OS partition:
/dev/mapper/vg-rootand/dev/mapper/vg-home🙃
But nobody uses /dev/sdX anymore (not after they wipe the wrong disk once anyway). They either use logical UUIDs or hardware WWN/serial.
idk man I use /dev/sdX when running commands interactively and PARTLABELs in my
/etc/fstab. All those letters and numbers in UUIDs are too much for my monkey brain to handle lolYeah, the point is “you can use either one”, instead of “we made the choice for you”
This is the goddamned truth
I always just derive the interface name from first principles. Like, if I want to know which interface will be used to get out to the internet in a script, I’ll just find the one that’s L2 adjacent with the default gateway. If I’m given an egress or cidr, I’ll just find the interface that has that IP. Modern
iproute2has a JSON output option which makes getting this information pretty trivial. Doing that means that it doesn’t matter what scheme your OS is using.I personally prefer the persistent names for Ethernet, although I don’t like them for WiFi. Luckily, it seems like my wireless adapter always just ends up as wlan0. I’m not sure why that’s the case, but it works out well in the end for me.
The predictable interface naming has solved a few issues at work, mainly in regards to when we have to work with expensive piece-of-shit (enterprise) systems, since they sometimes explode if your server changes interface names.
Normally wouldn’t be an issue, but a bunch of our hardware - multiple vendors and all - initialize the onboard NIC pretty late, which causes them to switch position almost every other boot.I’ve personally stopped caring about interface names nowadays though, I just use automation to shove NetworkManager onto the machine and use it to get a properly managed connection instead, so it can deal with all the stupid things that the hardware does.
expensive piece-of-shit (enterprise) systems, since they sometimes explode if your server changes interface names.
At no time in the past 25 years with Medium Iron have I seen something blow up on a reboot because an interface comes up late. We’d solved the issue of unreliable init order in 1998 - RH6? Zoot? Compaq, Supermicro, even embedded stuff on was-shit/still-shit gigabyte mobos. /etc/udev/rules.d handled this eliably, consistently and perfectly. Fight me.
You’re lucky to not have to deal with some of this hardware then, because it really feels like there are manufacturers who are determined to rediscover as many solved problems as they possibly can.
Got to spend way too much time last year with a certain piece of HPC hardware that can sometimes finish booting, and then sit idle at the login prompt for almost half a minute before the onboard NIC finally decides to appear on the PCI bus.
The most ‘amusing’ part is that it does have the onboard NIC functional during boot, since it’s a netbooted system. It just seems to go into some kind of hard reset when handing over to the OS.Of course, that’s really nothing compared to a couple of multi-socket storage servers we have, which sometime drop half the PCI bus on the floor when under certain kinds of load, requiring them to be unplugged from power entirely before the bus can be used again.
FIGHT! FIGHT! FIGHT! FIGHT! FIGHT!
with expensive piece-of-shit (enterprise) systems, since they sometimes explode if your server changes interface names.
Glass canons are brittle, huh?
Love the explainer to the meme.
Keep up the good work!
Thanks! Memes as education material / propaganda FTW
I was going to commend you as well. Top notch. I appreciate it
I came here to say this. I don’t really do networking so I don’t have much care for this issue, but the clarity of the explanation was enjoyable. Plus I learned a couple of little things too.
Small world thinking. Because you haven’t seen the need for it doesn’t mean it doesn’t exist. Also, did you lose your CTRL, C, and V keys?
Yes, because everyone has need of this solution, and wants to have to copy and paste interface names every time they need to touch them, rather than having deterministic naming be an option to enable for those who actually need it…
You know Linux isn’t just used by nerdy kids cosplaying as Mr Robot, right?
Kernel parameters? This is a udev thing, just change the udev rule.
