udev Abuse

I've probably mentioned before that I am a lazy systems administrator. So, I tend to like things be "self-documenting" and I like things to be as consistent as possible across platforms. I particularly like when a command that's basically common between two operating system versions gives me all of the same kinds of information - particularly if it's information that helps me avoid running multiple other commands.

I've also probably mentioned that, while I've managed a number of different UNIX and UNIX-like operating systems, over the years, the bulk of that has been on Sun systems (not that I prefer Sun systems - I actually always preferred IRIX with AIX a close second). So, I'm used to the Sun way of doing things (and, no, I will never accept that as now being the "Oracle way").

As someone coming from a heavy-Solaris background, I got used to NIC devices being assigned names that reflected the vendor/driver/architecture of the NIC in question. The fact that I could have ten NICs from ten different vendors, each with their own set of capabilities, but all just show up with a NIC device name of ethX, under Linux, always drove me kind of nuts. Yes, I know that I can get the information from other tools (`ethtool`, `kudzu`, looking through "/sys/class/net", etc.) but why should I have to when a crappy OS like Solaris allows me to get all that kind of stuff just by typing `ifconfig -a`?

Fortunately, Linux does provide to "fix" this grievous lack of self-documenting output. You just have to mess with the udev device-naming rules. These rules are stored under "/etc/udev/rules.d". In my particular case, I had a system that was equipped with a pair of dual-ported 10Gbps Mellanox Ethernet cards, a pair of Broadcom NetXtreme 10Gbps Ethernet NICs  and a quad-port Broadcom card with 1Gbps Ethernet NICs on it. Now, for what I was using the system for, I didn't particularly care about the 1Gbps NICs, but I did care about the 10GBps NICs. I had specific plans for laying out my system. Even more importantly, once I turned the system over, I didn't want to be pestered by (less Linux-savvy) people about "which device is which kind of NIC." So, I improvised. I created my own rule file, "61-net_custom.rules", to make udev give more self-documenting (Solaris-esque) names to the 10Gbps NICs. Two simple rules:

DRIVER=="bnx2x", NAME="bnx%n"
DRIVER=="mlx4_en", NAME="mlxiv%n"

And my Broadcom 10Gbps NICs started showing up as bnxX devices and my Mellanox 10Gbps NICs started showing up as mlxivX devices in my `ifconfig -a` output. Well... I did have to tell udev to update itself so it would rename the devices, but, you get the general idea. Unfortunately, Linux purists (not sure you have such given how much of a mongrel Linux is) would probably whine about this. Furthering the misfortune is that, because Linux doesn't have standard driver-specific device naming for NICs (e.g., unlike Solaris where someone sees "ce0" and they know it's the first Cerdes 1Gbps Ethernet NIC in the system), the names I've chosen won't necessarily be inherently meaningful. Oh well, that's what a run-book is for, I suppose.