Instructions to coordinate swap partition for linux

1.What is Swap?

Swap is virtual ram memory used when the physical ram of the server or vps is full or used in parallel with the physical ram memory to increase the memory capacity of the system.

2.Steps to create swap on centos system

B1.Check current swap partition on centos

swapon -s

B2.Check free disk space

df -h

B3. Check system ram.

free -m

B4.Create a swap partition

sudo dd if=/dev/zero of=/swapfile bs=1024 count=14336k

The above command is used to create a 14GB swap partition. Swap capacity will usually double the physical ram. Depending on how much disk system is left, we will customize it accordingly.

B5. Create swap partition

mkswap /swapfile

B6. Enable swap

swapon /swapfile

B6. Check the swap partition

B7. Set swap automatically enabled on reboot in the file /etc/fstab

echo /swapfile none swap defaults 0 0 >> /etc/fstab

B8 Re-authorize the swapfile file, only root has the right to edit the file

chown root:root /swapfile

chmod 600 /swapfile

B9.Configuring priority mode using swappiness

+swappiness = 0: swap is only used when RAM is used up.

+swappiness = 10: swap is used when RAM is 10%

+swappiness = 60: swap is used when the RAM is 60%.

+swappiness = 100: swap is preferred as RAM.

check the system's swap file usage
cat /proc/sys/vm/swappiness

edit parameter swappiness
sysctl vm.swappiness=10

Để giử nguyên thông số mỗi khi khởi động lại cần chỉnh sửa lại tham số trong file /etc/sysctl.conf
vi /etc/sysctl.conf
thêm dòng sau voà cuối file
vm.swappiness = 10