How to increase the swap space on Centos7

 In below command as you guys can see there is two hard disk onek is /dev/sda another one is /dev/sdb. Into the second hard dsik we are going to create a space 4Gigabyte for swap 

[root@centos7 ~]# fdisk -l

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: 0xd792ec1d

 

Device Boot      Start         End      Blocks   Id  System

/dev/sdb1            2048     8390655     4194304   83  Linux

/dev/sdb2         8390656    12584959     2097152   83  Linux

 

Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 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: 0x000aac81

 

   Device Boot      Start         End      Blocks   Id  System

/dev/sda1   *        2048      976895      487424   83  Linux

/dev/sda2          976896    43382783    21202944   83  Linux

/dev/sda3        43382784    59006975     7812096   82  Linux swap / Solaris

/dev/sda4        59006976    62914559     1953792    5  Extended

/dev/sda5        59011072    62914559     1951744   83  Linux

[root@centos7 ~]#

 

Now we are going to create a space for swap. As you can see in the below command, I have used 2 primary partition and 2 is still free. So that is why we are going to create the partition into primary. If you guys see that your primary partition is been used than you can go for extended partition.

 

[root@centos7 ~]# 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): n

Partition type:

   p   primary (2 primary, 0 extended, 2 free)

   e   extended

Select (default p): p

Partition number (3,4, default 3): 3

First sector (12584960-20971519, default 12584960):

Using default value 12584960

Last sector, +sectors or +size{K,M,G} (12584960-20971519, default 20971519): +4G

Using default value 20971519

Partition 3 of type Linux and of size 4 GiB is set

 

Command (m for help): p

 

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: 0xd792ec1d

 

   Device Boot      Start         End      Blocks   Id  System

/dev/sdb1            2048     8390655     4194304   83  Linux

/dev/sdb2         8390656    12584959     2097152   83  Linux

/dev/sdb3        12584960    20971519     4193280   83  Linux

First time when we create a partition it shows the id 83 but we have to choose the swap id that is 82.

 

Command (m for help): t

Partition number (1-3, default 3):

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: 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: 0xd792ec1d

 

   Device Boot      Start         End      Blocks   Id  System

/dev/sdb1            2048     8390655     4194304   83  Linux

/dev/sdb2         8390656    12584959     2097152   83  Linux

/dev/sdb3        12584960    20971519     4193280   82  Linux swap / Solaris

 

Command (m for help): w

The partition table has been altered!

 

Calling ioctl() to re-read partition table.

 

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.

The kernel still uses the old table. The new table will be used at

the next reboot or after you run partprobe(8) or kpartx(8)

Syncing disks.

[root@centos7 ~]# partprobe                   -> - inform the OS of partition table changes

[root@centos7 ~]# free -m                        -> - Display amount of free and used memory in the system

              total        used        free      shared  buff/cache   available

Mem:           3791         577        2566          11         646        3005

Swap:          7628           0        7628

[root@centos7 ~]# mkswap /dev/sdb3  -> - set up a Linux swap area

mkswap: /dev/sdb3: warning: wiping old swap signature.

Setting up swapspace version 1, size = 4193276 KiB

no label, UUID=016da57b-c639-4212-8c2c-9354d22f481d

[root@centos7 ~]# free -m

              total        used        free      shared  buff/cache   available

Mem:           3791         577        2567          11         646        3005

Swap:          7628           0        7628

[root@centos7 ~]# swapon /dev/sdb3   -> - enable/disable devices and files for paging and swapping

[root@centos7 ~]# free -m

              total        used        free      shared  buff/cache   available

Mem:           3791         580        2564          11         646        3002

Swap:         11723           0       11723          -> - here you can see the swap space increase

 

Then we need to entry the below line to the fstab.

[root@centos7 ~]# vi /etc/fstab

 

#

# /etc/fstab

# Created by anaconda on Tue Oct  6 12:45:09 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

#

UUID=bdcd1880-cb2d-46ca-843a-b578fb475602 /                       ext4    defaults        1 1

UUID=580ba544-de63-49e2-b12c-80bb6d6ff254 /boot                   ext4    defaults        1 2

UUID=c1aa9dd3-f9c6-410b-a31f-597afa71104b /tmp                    ext4    defaults        1 2

UUID=ca65c7fe-ee83-4076-ab6e-9e90e0482fa0 swap                    swap    defaults        0 0

/dev/sdb1       /database       ext4    defaults        0 0

/dev/sdb2       /storage        ext4    defaults        0 0

/dev/sd3        swap            swap    defaults        0 0

 

 

 

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