Wecome To Linux Swap Memory

How to Create Swap Partition on Linux

Swap memory is required when the system requires more memory than it is physically available. The kernel swaps out less used pages and gives memory to the current process that needs the memory immediately. So a page of memory is copied to the preconfigured space on the hard disk. Disk speed is much slower compared to memory speed. Swapping pages give more space for current applications in the memory (RAM) and make the application run faster.

Swap space is located on hard drives, which have a slower access time than physical memory. Swap space can be a dedicated swap partition or swap file, or a combination of both.

In this tutorial, we learn how to create a swap partition on a Linux system.

Create a swap partition

Lets first check disk space, then create a partition and followed by enabling swap.

1) Check disk space

CREATE A SWAP PARTITION IN LINUX

In this artical we are going to learn how to create a swap partition using command fdisk, Before that let me explain you what is the use of swap partition in Linux.

SWAP Partition is also known as SWAP memory, It is act as a Virtual Memory in Linux. When the physical memory of the system is full then Swap memory helps to system with a small amount of memory but we can’t consider it as a replacement of more memory.

Follow the steps to add a additional SWAP Partition:

Step: 1 Create a Partition

First check the available free disks to create a new partition by below command.

# To list the available free disks and created partitions.

[root@cloud_devopstraining_9160207373 ~]# fdisk -l

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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 /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x0003d1b7

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    83886079    40893440   8e  Linux LVM

Disk /dev/mapper/centos-root: 37.7 GB, 37706792960 bytes, 73646080 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 /dev/mapper/centos-swap: 4160 MB, 4160749568 bytes, 8126464 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

Partition List

Create a partition by below command.

[root@cloud_devopstraining_9160207373 ~]# fdisk /dev/sdb # To Create a new partition

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.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x047a6520.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-209715199, default 2048):     press enter
Using default value 2048     press enter
Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199):+5G
Partition 1 of type Linux and of size 5 GiB is set

Command (m for help): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   83  Linux

next step save and exit by applying w

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@cloud_devopstraining_9160207373 ~]#

create one more partition same as like above

Here we can enter the partition size in two ways in GB’s or in MB’s, for Example If you want to give the partition size as 1 GB then you can Enter +1G or +1024M.

here i am using 5GB for Swap..

[root@cloud_devopstraining_9160207373 ~]# fdisk /dev/sdb # To Create a new partition

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.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x047a6520.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-209715199, default 2048):     press enter
Using default value 2048     press enter
Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199):+5G
Partition 1 of type Linux and of size 5 GiB is set

Command (m for help): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   83  Linux

next step save and exit by applying w

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

[root@cloud_devopstraining_9160207373 ~]#

[root@cloud_devopstraining_9160207373 ~]# fdisk -l

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   83  Linux

Disk /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x0003d1b7

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    83886079    40893440   8e  Linux LVM

Disk /dev/mapper/centos-root: 37.7 GB, 37706792960 bytes, 73646080 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 /dev/mapper/centos-swap: 4160 MB, 4160749568 bytes, 8126464 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

[root@cloud_devopstraining_9160207373 ~]# fdisk -l

Assign a Number to Partition

[root@cloud_devopstraining_9160207373 ~]# fdisk /dev/sdb
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): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   83  Linux
/dev/sdb2        10487808    20973567     5242880   83  Linux

Command (m for help): t
Partition number (1,2, default 2): 1
Hex code (type L to list all codes): l

 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris
 1  FAT12           27  Hidden NTFS Win 82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     85  Linux extended  c7  Syrinx
 5  Extended        41  PPC PReP Boot   86  NTFS volume set da  Non-FS data
 6  FAT16           42  SFS             87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux plaintext de  Dell Utility
 8  AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt
 9  AIX bootable    4f  QNX4.x 3rd part 93  Amoeba          e1  DOS access
 a  OS/2 Boot Manag 50  OnTrack DM      94  Amoeba BBT      e3  DOS R/O
 b  W95 FAT32       51  OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor
 c  W95 FAT32 (LBA) 52  CP/M            a0  IBM Thinkpad hi eb  BeOS fs
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         ee  GPT
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f1  SpeedStor
12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f4  SpeedStor
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     f2  DOS secondary
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      fb  VMware VMFS
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fe  LANstep
1c  Hidden W95 FAT3 75  PC/IX           be  Solaris boot    ff  BBT
1e  Hidden W95 FAT1 80  Old Minix
Hex code (type L to list all codes): 82
Changed type of partition 'Linux' to 'Linux swap / Solaris'

Command (m for help): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   82  Linux swap / Solaris
/dev/sdb2        10487808    20973567     5242880   83  Linux

Creating Second Partition

So we create the partition successfully but our goal is to create a additional swap partition, for that we need to change the partition ID for that we have to enter "t" or for help we can go for "m".

Command (m for help): t

Here enter the available partition number for that disk and Press Enter.

Partition number (1,2, default 2):2

Hex code (type L to list all codes): 82
Changed type of partition 'Linux' to 'Linux swap / Solaris'

Command (m for help): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   82  Linux swap / Solaris
/dev/sdb2        10487808    20973567     5242880   82  Linux swap / Solaris

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

[root@cloud_devopstraining_9160207373 ~]#

[root@cloud_devopstraining_9160207373 ~]# fdisk -l

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x047a6520

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    10487807     5242880   82  Linux swap / Solaris
/dev/sdb2        10487808    20973567     5242880   82  Linux swap / Solaris

Disk /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x0003d1b7

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    83886079    40893440   8e  Linux LVM

Disk /dev/mapper/centos-root: 37.7 GB, 37706792960 bytes, 73646080 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 /dev/mapper/centos-swap: 4160 MB, 4160749568 bytes, 8126464 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

[root@cloud_devopstraining_9160207373 ~]#

In Linux based system after create a partition we suppose to restart the system to take effect but we can skip that by running "partprobe command"

# Changes take effect without restat the system

[root@cloud_devopstraining_9160207373 ~]# partprobe /dev/sdb 
[root@cloud_devopstraining_9160207373 ~]#

Before creating the swap memory

[root@cloud_devopstraining_9160207373 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           3.7G        1.7G        1.2G         24M        810M        1.7G
Swap:          3.9G          0B        3.9G
[root@clouddevops ~]#

we can use "blkid" command to check the Labels given to File Systems.

[root@cloud_devopstraining_9160207373 ~]# blkid

/dev/sda1: UUID="5b0b4da2-409f-44de-9434-46f1a3899ef1" TYPE="xfs"
/dev/sda2: UUID="S1ncTT-Mlnf-XSfH-J0yi-E6dd-CKri-0GAy4U" TYPE="LVM2_member"
/dev/sr0: UUID="2020-04-22-00-54-00-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos"
/dev/mapper/centos-root: UUID="bc6c57d9-0afa-4dbc-b989-7d3dd8139b41" TYPE="xfs"
/dev/mapper/centos-swap: UUID="32bed349-39dc-4f59-af3d-d1a623e1fd48" TYPE="swap"
[root@cloud_devopstraining_9160207373 ~]#

Step: 2 Create Swap Signature

Now Let’s create the swap Signature with "mkswap" command.

# To make a swap partition

Create Swap Partition with "mkswap"

L – To Label your Partition for Identification, This can be leave as a optional but Highly recommended.

[root@cloud_devopstraining_9160207373 ~]# mkswap /dev/sdb1 -L new-swap-part-one 
Setting up swapspace version 1, size = 5242876 KiB
mkswap: Label was truncated.
LABEL=new-swap-part-o, UUID=0b1264e7-ff27-477b-b029-cd7a52ec0241
[root@cloud_devopstraining_9160207373 ~]#

After creating the swap memory

we can use "blkid" command to check the Labels given to File Systems.

[root@cloud_devopstraining_9160207373 ~]# blkid
/dev/sda1: UUID="5b0b4da2-409f-44de-9434-46f1a3899ef1" TYPE="xfs"
/dev/sda2: UUID="S1ncTT-Mlnf-XSfH-J0yi-E6dd-CKri-0GAy4U" TYPE="LVM2_member"
/dev/sr0: UUID="2020-04-22-00-54-00-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos"
/dev/mapper/centos-root: UUID="bc6c57d9-0afa-4dbc-b989-7d3dd8139b41" TYPE="xfs"
/dev/mapper/centos-swap: UUID="32bed349-39dc-4f59-af3d-d1a623e1fd48" TYPE="swap"
/dev/sdb1: LABEL="new-swap-part-o" UUID="0b1264e7-ff27-477b-b029-cd7a52ec0241" TYPE="swap"
[root@cloud_devopstraining_9160207373 ~]#

Checking the Label of the Partition

Now enable the swapping and publish the swap space to the kernel by below command.

# Enable swapping on /dev/sdb1

[root@cloud_devopstraining_9160207373 ~]# swapon /dev/sdb1

After creating the swap memory Size

[root@cloud_devopstraining_9160207373 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           3.7G        915M        1.7G         25M        1.1G        2.5G
Swap:          8.9G          0B        8.9G
[root@cloud_devopstraining_9160207373 ~]#

OR we can use swapon -a to activate all swap partitions (Multiple swap Partitions)

Step: 3 Mount the Swap Partition

Now It’s time to add the newly created swap partition on "/etc/fstab" file to start the partition at startup.

# Edit the "fstab" file

[root@cloud_devopstraining_9160207373 ~]#vim /etc/fstab

#
# /etc/fstab
# Created by anaconda on Fri Jun 12 20:05:53 2020
#
# 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
#
/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=5b0b4da2-409f-44de-9434-46f1a3899ef1 /boot                   xfs     defaults        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
LABEL=new-swap-part-one swap    swap    defaults        0 0

Mounting SWAP Partition in fstab

We can check the swap status with below command.

[root@cloud_devopstraining_9160207373 ~]# swapon -s 
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition       4063228 0       -2
/dev/sdb1                               partition       5242876 0       -3
[root@cloud_devopstraining_9160207373 ~]#

"swapon -s" shows swap usage summary by device, Equivalent to "cat /proc/swaps"

[root@cloud_devopstraining_9160207373 ~]# cat /proc/swaps
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition       4063228 0       -2
/dev/sdb1                               partition       5242876 0       -3
[root@cloud_devopstraining_9160207373 ~]#

Checking SWAP Partition Usage

As we can see on above snapshot we have two swap partitions, out of which highlighted one is recently created and currently it’s usage status is 0.

We have another command to check the status of the swap memory is "free -m"

# Display amount of free and used memory in the system
[root@cloud_devopstraining_9160207373 ~]# free -m total used free shared buff/cache available Mem: 3770 874 1752 27 1144 2621 Swap: 9087 0 9087
OR
[root@cloud_devopstraining_9160207373 ~]# free -h total used free shared buff/cache available Mem: 3.7G 874M 1.7G 27M 1.1G 2.6G Swap: 8.9G 0B 8.9G [root@cloud_devopstraining_9160207373 ~]#

So This is how we can create a swap partition for better performance in our Linux System.

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Linux Tutorial

Linux

Interview Questions

Wecome To Linux Swap Memory

How to Create Swap Partition on Linux

Create a swap partition

1) Check disk space

Follow the steps to add a additional SWAP Partition:

Step: 1 Create a Partition

next step save and exit by applying w

next step save and exit by applying w

Step: 3 Mount the Swap Partition

Introduction to Operating System

Learn Latest Technologies

Cloud DevOps Services

Cloud DevOps deals also various great superiority facilities. For More Information Contact or Message Us on ☎ 9160207373 Mail us on ✉ support@devopscloud.org.in

We are Providing in House Training For Colleges and Corporate Compaines on Short Term and Long Term Classes.

Cloud DevOps offers College Campus Training on

✉ Mail your requirement at hr@clouddevops.in Duration: Short Term and Long Term