found on http://blog.kriptonium.com/2015/12/fedora-23-hibernate.html

To hibernate, info has to be added to grub2:

- step 1: identify the swap partition

blkid

- step 2: add it to default grub config

add it to /etc/default/grub in the GRUB\_CMDLINE_LINUX parameter

 GRUB_CMDLINE_LINUX="rhgb quiet resume=UUID=bt81a351-8421-1337-96ca-r9ab3605ff7c"

for me it worked better with /dev

 GRUB_CMDLINE_LINUX="rhgb quiet resume=/dev/sda5"

- step 3: remake/build the boot images

grub2-mkconfig -o /boot/grub2/grub.cfg

- step 4: try it