Friday, September 18, 2015

Changing how Linux Mint identifies network devices

I've been running Linux Mint 17.2 (mostly) happily on my old 2007 Thinkpad T61p.  However, even with 8GB of RAM and a SSD, it was a bit too sluggish for my tastes.  So I purchased a used T530 which is about 5-6 years newer and has an i7 CPU.

Swapping the SSD from one unit to the other was easy, and Linux Mint booted right up.  But I couldn't get a network connection (wired or wireless).

Troubleshooting step #1 was to boot up the Linux Mint 17.2 DVD and see whether it could see the network.  It saw both the wired ethernet port as well as the Thinkpad's WiFi.  So that indicated that there was no problem with the hardware and that Mint does support the Thinkpad network chips out-of-the-box.

Rebooted into the installed operating system.  I poked around a bit, then decided to just search /etc for any files containing 'eth0'.

# find /etc -type f -exec grep -H 'eth0' '{}' \;

That quickly lead me to the /etc/udev/rules.d/70-persistent-net.rules file.  Inside of there are lines that map the device (using the MAC) to names like 'eth0' 'eth1'.  Because this was a drive swap from the old to the new laptop, the old laptop's ethernet/wifi ports were in there already as eth0/wlan0.  Linux Mint then added new lines for the devices on the new laptop as eth1/wlan1.

The simple fix was to comment out the old SUBSYSTEM= lines, then change the NAME="" strings to be eth0 and wlan0.

After a reboot, everything worked as expected, without having to change anything else.

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