Google has taken security pretty seriously on the Pixel and Pixel XL which includes file-based encryption. For consumers, this is great since it makes for a more secure device. However, for developers, it makes things a bit complicated.
For anyone looking to flash ROMs, file-based encryption poses a challenge to installing a custom recovery. However, after some work was done to get around that, some developers have been able to get the popular custom recovery, TWRP, working on both Pixels.
The best gifts for Android users
Lead developer Ethan Yonker revealed in a post on Google+ (via Android Police) that TWRP for the Pixel and Pixel XL was now available and working, at least in an early alpha form. Things are still pretty buggy for now, and you actually risk wiping your device by using this. The biggest issue at the moment is with restores. If one doesn’t work correctly, the device may be wiped automatically, so if you do decide to load TWRP on your Pixel, you’ll want to keep everything backed up as best as you can, by using Google Photos, for example.
TWRP also works a bit differently on the Pixel, as Yonkers describes.
Pixel devices have 2 “slots” for ROMs / firmware. TWRP will detect whichever slot is currently active and use that slot for backup AND restore. There are buttons on the reboot page and under backup -> options to change slots. Changing the active slot will cause TWRP to switch which slot that TWRP is backing up or restoring. You can make a backup of slot A, switch to B, then restore the backup which will restore the backup of A to slot B. Changing the slot in TWRP also tells the bootloader to boot that slot.