Google Galaxy Nexus (GSM)
After spending hours trying to put PostmarketOS on my old phone I decided to write up some instructions to help someone save themselves some time.
Enter the bootloader by holding both volume buttons and the power button at the same time. You'll see a picture of an Android robot who is ready for surgery. Plug the phone into a PC with a USB cable.
Make sure your bootloader is unlocked by typing:
fastboot oem unlock
And say yes if any popup appears. It's been long since the warranty expired.
Install postmarket tools using pip3 install pmbootstrap. Then run:
pmbootstrap init
Then: pmbootstrap install
All the flashing instructions aren't correct for this device. This is because a typical image is bigger than the /system partition on this Android phone (the limit of the /system partition on a Nexus phone is 680MB). The bootloader refuses to install images that are bigger than the /system partition, even if you specify a different location.
fastboot flash -S 256M userdata ./workpath/chroot_native/home/pmos/rootfs/samsung-maguro.img
This can take a very long time. I don't know why. You ought to leave it for half an hour or more.
Once that's done:
pmbootstrap flasher boot