How Do I Create a Swap Partition or File in Linux?

Scenarios

This section describes how to create a swap partition on ECS running CentOS 6.8.

Constraints

A file of a specified size is to be created. Ensure that the system disk has enough available space.

Scenario 1: Creating a Swap Partition on a Block Storage Device

1. Run the following command to create a partition of 2 GB, for example:

   fdisk /dev/vdb

   Information similar to the following is displayed:

   Command (m for help): n
   Partition type:
      p   primary (0 primary, 0 extended, 4 free)
      e   extended
   Select (default p): 
   Using default response p
   Partition number (1-4, default 1): 
   First sector (2048-20971519, default 2048): 
   Using default value 2048
   Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): +2G
   Partition 1 of type Linux and of size 2 GiB is set

   Command (m for help): p
   
   Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 512 bytes
   I/O size (minimum/optimal): 512 bytes / 512 bytes
   Disk label type: dos
   Disk identifier: 0x1f02f438
   
      Device Boot      Start         End      Blocks   Id  System
        /dev/vdb1       2048     4196351     2097152   83   Linux
   
   Command (m for help): w
   The partition table has been altered!
   
   Calling ioctl() to re-read partition table.
   Syncing disks.

2. Run the following command to configure the newly created partition as swap space:

   mkswap /dev/vdb1

3. Run the following command to activate the swap partition:

   swapon /dev/vdb1

4. Run the following command to verify the activated swap:

   swapon -s

5. Run the following command to obtain the swap partition UUID:

   blkid |grep swap |awk '{print $2}'

   UUID="1ee90e3c-1538-453b-9240-ad430f835f6f" 

6. To mount the swap partition automatically upon system startup, add an entry for the swap partition to /etc/fstab.

   In this example, the swap partition UUID obtained in step 5 is 1ee90e3c-1538-453b-9240-ad430f835f6f. You need to run the following command:

   echo "UUID=1ee90e3c-1538-453b-9240-ad430f835f6f swap swap defaults 0 0" >>/etc/fstab

7. Run the following command to mount the swap partition:

   mount -a

Scenario 2: Creating a Swap Partition on a Block Storage Device Simulated by a File

The performance of the block storage device simulated by a file is not as good as that of the passthrough block storage device.