Udev Rule That Keeps A Network Device On

So, picture this: You've just moved into a new place, and you're all set up with your shiny new network device. Life's good, right? But then, one day, you wake up, and your device is MIA. It's vanished into the digital ether. What's going on?

Enter Udev, Stage Left

Now, before we dive into the nitty-gritty, let's meet our hero, udev. Udev is like the stage manager of your Linux system. It's responsible for managing device files and rules. It's the unsung hero, the backstage whisperer, making sure everything runs smoothly.

So, when your network device goes AWOL, it's often because udev doesn't have a rule to keep it around. It's like udev's saying, "I don't know what this thing is, so I'm gonna kick it to the curb." But don't worry, we're gonna change that.

Why Does Udev Do This?

Well, udev's just following orders. It's designed to be dynamic, to handle hotplugging - that's tech talk for when you plug or unplug devices. But sometimes, it can be a bit too eager to clean up. It's like that one friend who tidies up your place while you're out, but then can't find your stuff because they put it all away 'neatly'.

But fear not! We're gonna teach udev to recognize your network device and keep it around. Let's get started.

Meet the Rule Maker

To teach udev, we're gonna use a little tool called udevadm. It's like udev's teacher, helping it learn new rules. First, we need to find out what udev sees when your network device is plugged in.

Fire up a terminal and type: udevadm info --query=all --name=/sys/class/net/YOUR_DEVICE_HERE. Replace YOUR_DEVICE_HERE with your network device's name. You'll see a bunch of info, but we're interested in the ID_PATH and ID_NAME lines.

For example, you might see something like this:

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ID_PATH=net
ID_NAME=eth0

Now, we know udev sees your device as net/eth0. Let's use this info to create a rule.

Crafting the Rule

We're gonna create a new file in the /etc/udev/rules.d directory. This is where udev stores its rules. Let's use nano to edit the file:

sudo nano /etc/udev/rules.d/99-my-network-device.rules

In this file, we're gonna write a new rule. It should look something like this:

ACTION=="add", KERNEL=="net/YOUR_DEVICE_HERE", ATTR{address}, RUN+="/sbin/ip link set $kernel dev $kernel up"

Replace YOUR_DEVICE_HERE with your device's name. This rule tells udev to keep your device around and bring it up when it's added.

Now, save and close the file. Then, reload the udev rules:

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sudo udevadm control --reload-rules

And, just to be sure, restart the udev service:

sudo systemctl restart systemd-udevd

And... That's a Wrap!

And there you have it! Your network device should now stick around, even after a reboot. You've just taught udev a new trick. You're like the digital dog whisperer!

But remember, every system is unique, so if you're having trouble, don't hesitate to ask for help. The Linux community is full of friendly folks who love helping out.

So, go forth, network device owner, and enjoy your newly tamed udev. And remember, with great power comes great responsibility. Don't go creating rules willy-nilly. Keep your rules file tidy, and udev will be your best friend.