linux Centos7 adds swap partition detail

Note :(Redhat5 official recommendation)

RAM < =4G,swap=2G;RAM > 4G, < 16G,swap=4G;RAM > 16G, < 64G,swap=8G;RAM > 64G, < 256G,swap=16G

Redhat6/7 Official recommendation RAM < =2G,swap=2*RAM;RAM > 2G, < 8G,swap=RAM;RAM > 8G, < 64G,swap > =4G;RAM > =64G,swap > = 4 G; (Sleep state is another consideration)

There are two ways to add swap: 1. Add swap partition; 2. 2. Add swap file;

Method 1.

Adding swap space can be used to solve the problem that some services are forced to shut down due to excessive physical memory usage on the system

Add 1 hard disk of 200M (0.2ES52en) in shutdown state

View the swap size

free -m // or  cat /proc/meminfo | grep -i swap  or  fdisk -l  or swap -s

So if you look at the new hard disk that was added here the new disk that was added was sdb (see capacity)

cat /proc/partitions

Create the partition and set it to swap format

fdisk /dev/sdb

n // Create partitions  
p // Create primary partition  
1 // Create partitions 1 
 Press enter twice  // Initial sector and Last Sector selection default 
t // Convert partition format  
82 // convert swap space  
p // View the partition results created  
w // Save the exit 

Format to swap space

mkswap /dev/sdb1

Enable swap

swapon /dev/sdb1

The edit profile is set to boot auto mount

vim /etc/fstab

Add the following to save and exit

/dev/sdb1 swap swap defaults 0 0

Set to automatically enable all swap Spaces

swapon -a

Restart the validation

reboot

Check the swap size again

cat /proc/partitions

0

Note: You can see that swap has changed

Method 2.

Adding swap space can be used to solve the problem of insufficient physical memory on the system causing some services to be forced to shut down

View the swap size

cat /proc/partitions

1

Note: If swap displays 0 or does not output swap, the system does not add swap space

Create the swap file

cat /proc/partitions

2

Set to allow root users to work with this file only

chmod 600 /etc/swap

Check file sizes and permissions

cat /proc/partitions

4

Set the file to swap

cat /proc/partitions

5

Enable the swap file

cat /proc/partitions

6

Make the swap file permanent

cat /proc/partitions

7

Add:

/etc/swap swap swap defaults 0 0

Change the swap configuration

cat /proc/partitions

9

Modify if there is, add if there is no :(modify the value as required)

vm.swappiness=30 // A higher value indicates a greater propensity to use swap space 

Restart to take effect

reboot

Check the swap size again

free -m // or  cat /proc/meminfo | grep -i swap  or  fdisk -l  or swap -s

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