--------- SWAP, ZRAM --------- 

- CHECKING SWAP
- LIVE SWAP CHANGES
- SWAPPINESS
- DISABLING SWAP
- SWAP ON ZRAM


#======= CHECKING SWAP =================================================

# Used/free memory
~] free -h

# List mounted partitions
~] lsblk

#======= LIVE SWAP CHANGES =============================================

# disable swap
~] swapoff -a

# To set the new value to 10:
# make changes as root
~] echo 10 > /proc/sys/vm/swappiness

# To turn swap back on:
~] swapon -a



#=======  SWAPPINESS ===================================================

Swappiness is a Linux kernel parameter that controls the relative 
weight given to swapping out runtime memory. Swappiness represents the 
percentage of the free memory before activating swap. The lower the 
value, the less swapping is used and the more memory pages are kept in 
physical memory.

vm.swappiness = 0 	Kernel version 3.5 and over: disables swapping.
                    Prior to version 3.5: The kernel will swap only
                    to avoid an out of memory condition.
vm.swappiness = 1 	Kernel version 3.5 and over: Minimum swappiness
                    without disabling it entirely
vm.swappiness = 60 	The default value.
vm.swappiness = 100 The kernel will swap aggressively.


To change swappiness:

1. create/edit file /etc/sysctl.d/99-vmswap.conf ;
2. Insert/edit the line with aproriate value, e.g.:
   vm.swappiness=10
   

#=======  DISABLING SWAP ===============================================

##=======  Non-GPT disks:

Simply commenting out the corresponding line in /etc/fstab to prevent 
swap from mounting on reboot, e.g.:

#UUID=dcaa4979-b495-44d2-a117-360b485a35a0 none                    swap    defaults        0 0

##=======  GPT disks:

Systemd activates swap partitions based on two different mechanisms. 
Both are executables in /usr/lib/systemd/system-generators. The 
generators are run on start-up and create native systemd units for 
mounts. The first, systemd-fstab-generator, reads the fstab to generate 
units, including a unit for swap. The second, 
systemd-gpt-auto-generator inspects the root disk to generate units. It 
operates on GPT disks only, and can identify swap partitions by their 
type GUID.

To deactivate specific swap space:

~] swapoff /dev/sdxy

Alternatively use the -a switch to deactivate all swap space.

Since swap is managed by systemd, it will be activated again on the 
next system startup. To disable the automatic activation of detected 
swap space permanently, run systemctl --type swap to find the 
responsible .swap unit and mask it.

Check the status:

~] systemctl status *swap

or :

~] systemctl --type swap

Then disable the service:

~] systemctl mask  "dev-*.swap"

Does not work for Fedora 36. You shoud delete SWAP partition.

##=======  SWAP ON ZRAM ================================================

How can swap on zram be disabled?


Immediately:

~] systemctl stop swap-create@zram0


Permanently:

~] touch /etc/systemd/zram-generator.conf
	or
~] dnf remove zram-generator-defaults

##=======  Release Notes

A “swap” partition is not created by default at installation time.
Instead, a “zram” device is created, and swap enabled on it during
start-up. “zram” is a RAM drive that uses compression. See

~] man zram-generator

for a brief overview of its function. The “swap-on-zram” feature can be
disabled with

~] touch /etc/systemd/zram-generator.conf

and reenabled by removing this file, and customized by editing it. See

~] man zram-generator.conf

for configuration information, including a description of the default
configuration plus ASCII art.


##=======  References ==================================================

https://forums.fedoraforum.org/showthread.php?319350-Reducing-swappiness
https://fedoraproject.org/wiki/Changes/SwapOnZRAM#How_can_it_be_disabled.3F
https://unix.stackexchange.com/questions/671940/disabling-swap-on-debian-permanently
https://www.mybluelinux.com/how-disable-swap-in-debian-or-linux-system/
https://www.tecmint.com/disable-swap-partition-in-centos-ubuntu/