My disk has been verging on 100% capacity for a long time. I’ve always known that the problem is Docker, but I finally got around to resolving it.
> docker system prune
This took a while to run, but cleared an embarassing amount of space.
I followed this up with optimizing Docker’s ext4.vhdx file.
The top answers on Stack Overflow point to an Optimize-Vhd command,
which wasn’t found on my system. Instead, I followed
these steps.
Shut down Docker Desktop, then:
> wsl --shutdown
> diskpart
A new shell window opens with the Diskpart program running. Then from the Diskpart command line:
> select vdisk file="C:\Users\…\ext4.vhdx"
> attach vdisk readonly
> compact vdisk
> detach vdisk
> exit