I installed the wrong WiFi driver, then "broke" Ethernet by unplugging it Draft
The goal
Get WiFi working on the 2017 iMac under Arch Linux. Broadcom chip, Linux, WiFi — you already know this story is going to hurt.
Hardware and cost
- 2017 27" iMac with Broadcom BCM43602 WiFi
Software stack
- Arch Linux (Omarchy)
- brcmfmac — the in-kernel driver that actually supports the BCM43602
What broke and how it was fixed
The BCM43602 uses the in-kernel brcmfmac driver. Not broadcom-wl. I was caught mid-install of broadcom-wl-dkms — the wrong driver, the one every outdated forum post still recommends.
Fix was simple: pacman -R broadcom-wl-dkms to remove it, confirm no blacklist was left behind, and the wireless interface wlp3s0 came up on its own with the right driver.
And then the second act of the tragedy: Ethernet "vanished" with a NO-CARRIER status. Cue ten minutes of driver suspicion — before discovering that I had accidentally unplugged the Ethernet cable myself while reaching around the back for the router's WiFi password. The network wasn't broken. My hands were.
Verdict
Two lessons, one post: check which driver your specific Broadcom chip actually needs before installing anything (BCM43602 = brcmfmac, in-kernel, no DKMS required), and when the link goes down, check the cable before the kernel. Especially when you've been reaching behind the machine.