How could I enable hibernation on a Dell Inspiron 5548 running ubuntu focal?

To enable Hibernation in 20.04 using swapfile:

Confirm swapfile size matches RAM size

• Check the swap that is in use:

  sudo swapon -s
  

• If swap partition(s) are found:

  sudo swapoff -a
  sudo nano -Bw /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 swapfile:

  sudo fallocate -l XG /swapfile*
  

  where X is swapfile's size in GB:

  sudo mkswap /swapfile
  sudo chmod 0600 /swapfile
  sudo swapon /swapfile
  

• Reboot:

  sudo reboot
  

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.

Note that 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 swap file can alternatively be created using dd:

sudo dd if=/dev/zero of=/swapfile bs=1G count=8

An error when using dd may overwrite your HDD.