I've been running Arch Linux on my Raspberry Pi 3 Model B for several years. I recently did a software upgrage, using yay. There were quite a few items as I remember. Upon rebooting, the computer did not return to availability on the network, so I connected the HDMI to a screen. Upon rebooting, I saw the usual rainbow square, then a lot of text that scrolled rapidly by and just disappeared.
I've removed the MicroSD card, run fsck on both partitions, and looked at their contents. Everything looks normal as far as I can tell.
journalctl on the journal file does not provide timely enough information. I assume the really useful information, if any, would be in the kernel ring buffer, which isn't available.
So: can anyone suggest a way to find out what's happening?
