TODO for suspend to disk (hibernate)

[paigeadelethompson]

It's necesarry to have a swapfile which apparently can all be done with just a swap file on BTRFS:

bash-5.2# cd /var/swap/
bash-5.2# lsattr 
---------------C------ ./swapfile
bash-5.2# 

However, it was not real obvious or easy to get this this to work correctly (you can only set NOCOW on a zero-length file which means you must first touch swapfile then chattr +C swapfile AND then fallocate -l 4g /var/swap/swapfile to specify the physical extents of the swap file,

• mkswap /var/swap/swapfile
• swapon /var/swap/swapfile
• in /etc/fstab you specify: /var/swap/swapfile none swap 0 0
• you need to get a UUID: findmnt -no UUID -T /var/swap/swapfile and specify in /boot/cmdline.txt the resume argument: resume=UUID=c1f08e11-c1de-4477-92b3-b2ba17c6eec4 and evidently this works but it still needs to be tested with Void's zzz package and associated user hooks

[paigeadelethompson]

This should also be set to zero to prevent pages from actually getting swapped:

➜  ~ sudo sysctl -a | grep swap
vm.swappiness = 0
➜  ~ 

default for it is 60, anyway this will require ensuring sysctl -f /etc/sysctl.conf is run at boot unless it can be overridden in the kernel build.. but it should probably just stay sysctl