hibernate.md

Please Refer to swap.md before reading this file.

Kernel Boot Parameters

The kernel must know how to find the swap file in order to perform hibernation correctly, this is done by editing the bootloader's file /etc/default/grub and adding the resume= and resume_offset= kernel startup parameters. Where resume= is the partition where the swap file is located and the resume_offset= is the physical offset on the (disk?/partition?).

We'll use the findmnt command to determine the partition UUID where swap is located, which is the root partition / in this case.

Note: We can also use the partition block file path /dev/sda2 instead of the UUID

findmnt -no UUID -T /swap
6bbedf14-9059-4c0a-afa8-e688d2c51203

And to find the physical offset we'll use the filefrag command, in this case the physical offset is 1458176

filefrag -v /swap

# The output is

Filesystem type is: ef53
File size of /swap is 8589934592 (2097152 blocks of 4096 bytes)
 ext:     logical_offset:        physical_offset: length:   expected: flags:
   0:        0..    4095:    1458176..   1462271:   4096:

At the end the GRUB_CMDLINE_LINUX= variable in /etc/default/grub will look like this

GRUB_CMDLINE_LINUX="intel_iommu=on resume=UUID=6bbedf14-9059-4c0a-afa8-e688d2c51203 resume_offset=1458176"

Last but no least, we must regenerate the /boot/grub.cfg file

grub-mkconfig -o /boot/grub.cfg

Regenerating RamFS

To do so the mkinitcpio bash script will be used, after editing the /etc/mkinitcpio.conf by adding the hook resume in the HOOKS= variable

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

After that is done, let's regenerate the ramfs

doas mkinitcpio -p linux

Enabling Hibernation on Lid Close

Edit /etc/systemd/logind.conf by uncommenting then changing the variables HandleLidSwitch=

HandleLidSwitch=hibernate

# Setting this will cause the device to hibernate automatically (Not Required)
# After the IdleActionSec time
IdleAction=hibernate
IdleActionSec=[TIME]