Create swap space on Ubuntu

** Create swap **
- Check swap info
> swapon --show
> free -h

- Check available space disk
> df -h

- Create swap
> sudo fallocate -l 2G /swapfile

- Verify
> ls -lh /swapfile
Output:
-rw-r--r-- 1 root root 2.0G Oct  8 04:57 /swapfile

- Enabling the swap file
> sudo chmod 600 /swapfile

- Mark the file as swap space
> mkswap /swapfile
Output:
Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)
no label, UUID=f05afaa0-48ba-453b-bcb1-f5d59a9e75f7

- Enable the swap file
> swapon /swapfile

- Verify info
> swapon --show
Output:
NAME      TYPE SIZE USED PRIO
/swapfile file   2G   0B   -1

- Save config when system reboot
> echo /swapfile none swap defaults 0 0 >> /etc/fstab

- Config the threshold RAM to using SWAP
/**
 * swappiness = 0 : When RAM empty
 * swappiness = 10: When RAM remaining 10%. [Recommend]
 * swappiness = 60: When RAM remaining 60%
 * swappiness = 100: Using swap same ram
**/
- Check swappiness
> cat /proc/sys/vm/swappiness
Output
60

- Set swappiness
> sysctl vm.swappiness=10

- Verify
> cat /proc/sys/vm/swappiness

- Save when system reboot
> nano /etc/sysctl.conf
- add more line in the end: 
vm.swappiness = 10

- Config more vfs_cache_pressure

** Change space swap **
- Turn off swap
> swapoff /swapfile

- Remove swap
> rm -f /swapfile

- Renew swap
> sudo dd if=/dev/zero of=/swapfile bs=1024 count=2048k

- Make swap
> mkswap /swapfile

- Enable swap
> swapon /swapfile

- chmod, chown file
> chown root:root /swapfile 
> chmod 0600 /swapfile

- Verify info
> swapon -s