Hibernate on Linux

Source: https://wiki.archlinux.org/title/Power_management/Suspend_and_hibernate#Instantaneous_wakeups_from_suspend

To be able to put your PC in hibernate, you will need some things to do: 1. Have a swap the same size or bigger than your RAM. 2. Set the kernel parameters. 3. Configure the initramfs to include the resume hook.

Set the kernel parameters

If you are using a swap file, it is required to set the resume=swap_device and additionally a resume_offset=swap_file_offset kernel parameters.

The swap_device can be identified with the following command:

findmnt -no UUID -T /swapfile

This will give you the UUID of the swap file, and this is what you should be putting in your kernel parameters:

resume=UUID=4209c845-f495-4c43-8a03-5363dd433153

The following command may be used to identify swap_file_offset:

filefrag -v /swapfile | awk '{ if($1=="0:"){print substr($4, 1, length($4)-2)} }'

Then you put that in the /etc/default/grub file between the quotes of the GRUB_CMDLINE_LINUX_DEFAULT line. For example:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash resume=UUID=4209c845-f495-4c43-8a03-5363dd433153 resume_offset=4392394"

After that, regenerate the grub.cfg file with:

grub-mkconfig -o /boot/grub/grub.cfg

Configure the initramfs

When an initramfs with the base hook is used, which is the default, the resume hook is required in /etc/mkinitcpio.conf. Whether by label or by UUID, the swap partition is referred to with a udev device node, so the resume hook must go after the udev hook. This example was made starting from the default hook configuration:

HOOKS=(base udev autodetect keyboard modconf block filesystems resume fsck)

Remember to regenerate the initramfs for these changes to take effect:

mkinitcpio -p linux