Where is resume file?

Swap Partition to Swapfile with Hibernation in 20.04:

Increase swapfile size to match RAM size up to 8GB.

• Check the swap that is in use:

  sudo swapon -s

• If swap partition(s) found:

  sudo swapoff -a

  sudo nano -Bw /etc/fstab

• In /etc/fstab add "# " before the UUID of the swap partition(s):

  # UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX none swap sw 0 0

• Add a line for the swapfile, if one does not exist:

  swapfile none swap sw 0 0

• Create the swap file:

  sudo fallocate -l XG /swapfile*

Where X is the swapfile size in GB

    sudo mkswap /swapfile

    sudo chown 0600 /swapfile

    sudo swapon /swapfile

• Reboot:

  sudo reboot

Setup Hibernation (Optional)

Add resume location and offset to grub.cfg:

• Edit /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash resume=UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX resume_offset=XXXXX"

• Use UUID from root.

• Use offset from sudo filefrag -v /swapfile |grep " 0:"| awk '{print $4}'

• Update GRUB sudo update-grub

• Test hibernation sudo systemctl hibernate

A hibernate button can be added using gnome extensions.

*There is a slight possibility of getting holes in a swapfile when creating it with fallocate. /var/log/syslog can be searched for the phrase swapon: swapfile has holes to ensure there will be no data loss.

A swapfile can alternatively be created using dd: sudo dd if=/dev/zero of=/swapfile bs=1G count=8 Caution: An error when using dd may overwrite your HDD

You'll have one only after you hibernate your system (instead of shutting down), otherwise you don't have one.

Not having one is normal (if you watch the boot messages, you'll note an error with it not being found which leads to the normal cold boot). The file's presence tells the system it was hibernated and a resume is required (instead of cold-boot).

It doesn't relate to the swapfile/swap-partition change

https://wiki.ubuntu.com/DebuggingKernelHibernate