How to create 500 MB swap partition in RHEL 7

Step 1: Check current swap space in OS

[root@rhel7 ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           987        805        181         13          0        353
-/+ buffers/cache:        451        535
Swap:         2047          0       2047
[root@rhel7 ~]#

Step 2: Now check disk space we will create swap space and necessary action 

[root@rhel7 ~]# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 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: 0x000aab0f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    21506047    10240000   83  Linux
/dev/sda3        21506048    25700351     2097152   82  Linux swap / Solaris
/dev/sda4        25700352    41943039     8121344    5  Extended
/dev/sda5        25702400    40038399     7168000   83  Linux

Disk /dev/sdb: 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: 0x44245958

   Device Boot      Start         End      Blocks   Id  System

Disk /dev/sdc: 5368 MB, 5368709120 bytes, 10485760 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: 0x6cba2f17

   Device Boot      Start         End      Blocks   Id  System
[root@rhel7 ~]#

Note: Here we will consider /dev/sdc for swap partition

[root@rhel7 ~]# fdisk /dev/sdc
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n   [For new partition creation]
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p):                [Primary partition]
Using default response p
Partition number (1-4, default 1):
First sector (2048-10485759, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-10485759, default 10485759): +500M         [500MB Partition size]
Partition 1 of type Linux and of size 500 MiB is set

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 82           [82 code for Linux swap partition]
Changed type of partition 'Linux' to 'Linux swap / Solaris'

Command (m for help): p                               [Print partition info of /dev/sdc]

Disk /dev/sdc: 5368 MB, 5368709120 bytes, 10485760 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: 0x6cba2f17

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048     1026047      512000   82  Linux swap / Solaris

Command (m for help): w                                [Write and save new partition]
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@rhel7 ~]#

Step 3:  Inform the OS of partition table changes

[root@rhel7 ~]# partprobe

Step 4: Now setup this newly created partition as swap area using the mkswap command 
                            
[root@rhel7 ~]# mkswap /dev/sdc1
mkswap: /dev/sdc1: warning: wiping old swap signature.
Setting up swapspace version 1, size = 511996 KiB

no label, UUID=5fe81d10-f220-4572-80b3-56f65addefb2

[root@rhel7 ~]# vim /etc/fstab

[root@rhel7 ~]

[root@rhel7 ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Sun Dec 20 10:52:45 2015
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=3861c2f0-4524-4b79-83bf-75be5412b10b /                       xfs     defaults        1 1
UUID=90c2e689-ad4e-4c54-a470-f6dffa4be07d /boot                   xfs     defaults        1 2
UUID=2cd6288f-86f3-4feb-ae99-e77642c0d205 /data                   xfs     defaults        1 2
UUID=f5c7ed53-48b9-48e0-b47d-527bf7bb88fa swap                    swap    defaults        0 0
UUID="5fe81d10-f220-4572-80b3-56f65addefb2" swap        swap    defaults        0       0


[root@rhel7 ~]#

Step 5: Enable the swap partition for usage using swapon command as shown below.

[root@rhel7 ~]# swapon /dev/sdc1

Step 6: Now check swap space added or not 

[root@rhel7 ~]# free -m

             total       used       free     shared    buffers     cached

Mem:           987        882        104          7          1        354

-/+ buffers/cache:        526        460

Swap:         2547          0       2547

[root@rhel7 ~]#

Verify whether the newly created swap area is available for your use.

[root@rhel7 ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda3                               partition       2097148 0       -1
/dev/sdc1                               partition       511996  0       -2
[root@rhel7 ~]#