Hibernation? Using it?

[2disbetter]

@Viandant

Therefore we have to boot into a system that uses a different root partition. The Ubuntu installation ISO is well suited for this purpose. So boot from the Ubuntu installation ISO. Select «Try Ubuntu». After the desktop has appeared, click on the disk symbol with the lock at the left edge of the screen. You should be prompted for the password of your encrypted partition. Enter it. Then use the terminal to change the sizes of the logical volumes like this:

sudo lvresize -L-5G -r /dev/mapper/vgubuntu-root
sudo lvresize -l100%FREE /dev/mapper/vgubuntu-swap_1
sudo mkswap /dev/mapper/vgubuntu-swap_1

Adapt the size by which the root partition is decreased (5G in the example) to your needs. You also can enter it with other units, for example in megabytes with the M suffix.

Note, the -r is important. Without it the file system size remains unchanged and decreasing the logical volume would cut off a part leaving you with a corrupted file system.

After removing the installation ISO and rebooting, you should be able to start hibernation with this command:

sudo systemctl hibernate

This was the missing piece to the puzzle I was looking for. To be clear this allows someone to take the default swap file (vgubuntu/swap_1) that is made during the Ubuntu install process and use it for hibernation purposes. The benefits of which are the speed the NVME supports, and your swap file will be encrypted, if you set up luks, as your entire drive is already.

One caveat though is unlike a standard swap file used on another drive or partition, where using the logical drive location is necessary as @jean points out here:

@jean

Solved !
In the grub config, I set resume=UUID=xxxxx as all guides tell, but for an encrypted swap you actually have to use the device path instead (resume=/dev/mapper/luks-a0a21122-091b-46ed-89a5-a721e59ae4db for me)

you still need to use the resume=UUID= format with the vgubuntu swap file.

Outside of this you will have beautiful hibernation service on your Framework.

Now back to seeing if I can get hibernation support added to the pi OS kernel.