I struggled with a similar issue in Debian 9, installed on a Lenovo G40-30 Laptop. I went into Hibernate/Sleep and trying to initiate again the screen didn't show up although everything seemed working.
The solution is actually quite simple. It seems Linux OSs, in particular Debian and Ubuntu need at least a 4+GB swap partition for Hibernate/Sleep to work properly. If you installed with "default" configuration it will create a Swap the same size of your actual RAM (in practice a little less). So if you have a laptop with less or equal to 4 Gb RAM and installed "default" configuration, you are probably trying to solve this issue.
Swap allocation in Linux work in two ways:
1) in the form of a SWAP PARTITION in your hardrive.
2) in the form of a SWAP FILE.
YOU CAN CREATE THE SWAP FILE AS FOLLOWS:
sudo swapon --show
shows if you have enabled the swap option. If not look up how to do this.
sudo fallocate -l 1G /swapfile
sets the size of the swap you add to 1Gb, change to the value you need.
sudo chmod 600 /swapfile # sets the file to be owned by root sudo mkswap /swapfile # mkswap tool to allocate swap in the file sudo swapon /swapfile # activate the swap sudo nano /etc/fstab # open the file to make changes permanent
Add the line /swapfile swap swap defaults 0 0 to the file /etc/fstab:
sudo swapon --show # show if its working sudo free -h # show Memory and Swap
IF YOU WANT TO UNDO CHANGES JUST:
sudo swapoff -v /swapfile
remove the line from /etc/fstab file: /swapfile swap swap defaults 0 0
sudo rm /swapfile # remove the swap file
SWAP SIZES ACCORDING TO RAM:
I can indicate the following table with some recommended SWAP sizes according to your RAM. Last 3 columns are SWAP spaces:
RAM No hibernation With Hibernation Maximum 1GB 1GB 2GB 2GB 2GB 1GB 3GB 4GB 3GB 2GB 5GB 6GB 4GB 2GB 6GB 8GB 5GB 2GB 7GB 10GB 6GB 2GB 8GB 12GB 8GB 3GB 11GB 16GB 12GB 3GB 15GB 24GB 16GB 4GB 20GB 32GB 24GB 5GB 29GB 48GB 32GB 6GB 38GB 64GB 64GB 8GB 72GB 128GB 128GB 11GB 139GB 256GB 256GB 16GB 272GB 512GB 512GB 23GB 535GB 1TB 1TB 32GB 1056GB 2TB 2TB 46GB 2094GB 4TB 4TB 64GB 4160GB 8TB 8TB 91GB 8283GB 16TB
MORE INFORMATION:
you can find thorough information on recommended SWAP sizes according to your RAM in the following link:
https://askubuntu.com/questions/594054/how-much-swap-should-i-take-for-1gb-to-8tb-of-ram-on-14-04-or-higher
Credit is due for the table I added here.
