Swap Partation
In this article we will create swap space using
fdisk command. In previous article you have learnt how to create partitions
with fdisk, just one more additional step is required to set up that partition
for swap space. Before you start making a swap partition make sure that you
have enough free and unparted space to create new partition.
Swap memory is required when 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 pre-configured space on the hard disk. Disk speed is
much slower compared to memory speed. Swapping pages give more space for
current application in the memory (RAM) and make application run faster.
Creating
a swap partition
Create a normal partition using a fdsik command and
change hex code to make it swap partition.
- The hex code for SWAP is 82.
- Note: To change the hex code use t in fdisk and list all the hex code use l
[root@linuxelearn
~]# fdisk /dev/sda
WARNING:
DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c')
and change display units to
sectors (command 'u').
Command (m for help): n
First
cylinder (1757-2088, default 1757):
Using
default value 1757
Last
cylinder, +cylinders or +size{K,M,G} (1757-2088, default 2088): +500M
Command (m for help): t
Partition
number (1-7): 7
Hex
code (type L to list codes): 82
Changed
system type of partition 8 to 82 (Linux swap / Solaris)
Command (m for help): p
Disk
/dev/sda: 17.2 GB, 17179869184 bytes
255
heads, 63 sectors/track, 2088 cylinders
Units
= cylinders of 16065 * 512 = 8225280 bytes
Sector
size (logical/physical): 512 bytes / 512 bytes
I/O
size (minimum/optimal): 512 bytes / 512 bytes
Disk
identifier: 0x000efa3d
Device Boot Start End Blocks
Id System
/dev/sda1 *
1 26 204800
83 Linux
Partition
1 does not end on cylinder boundary.
/dev/sda2 26 1301 10240000
83 Linux
/dev/sda3 1301 1562 2097152
82 Linux swap / Solaris
/dev/sda4 1562 2088 4228884 5
Extended
/dev/sda5 1562 1626 517837+
82 Linux swap / Solaris
/dev/sda6 1627 1691 522081
8e Linux LVM
/dev/sda7 1692 1756 522081
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@linuxelearn
~]#
|
Format
the newly created swap partition with swap file system
#mkswap /dev/sda7
[root@linuxelearn
~]# mkswap /dev/sda7
Setting
up swapspace version 1, size = 522076 KiB
no
label, UUID=ca233655-0666-4653-9768-f98fe7e9cb45
[root@linuxelearn
~]#
|
Start
/ turn on the newly created swap space and verify it.
To turn on the swap space the syntax is
#swapon /dev/sda7
[root@linuxelearn
~]# swapon /dev/sda7
|
To
Verify the newly added swap space use the below commands:
#cat /proc/swaps
or
#swapon –s
[root@linuxelearn
~]# swapon -s
Filename Type Size Used
Priority
/dev/sda3 partition 2097144 0 -1
/dev/sda5 partition 517828
0 -2
/dev/sda8 partition 522072
0 -3
[root@linuxelearn
~]# free -m
total used free shared
buffers cached
Mem: 997 512 484 0 75 159
-/+
buffers/cache: 277 720
Swap: 3063 0
3063
[root@linuxelearn
~]#
|
Making
the newly created Swap Partition to mount after reboot
In order to make the swap partition mount automatic
after reboot, we need to make an entry in /etc/fstab
file.
#vim
/etc/fstab
#
#
/etc/fstab
#
Created by anaconda on Sat Aug 13 17:36:51 2016
#
#
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=4afa457a-d662-4e89-b4e2-09303c44c3eb
/ ext4 defaults 1 1
UUID=752c2f33-fe60-4269-9480-b27260fc3777
/boot ext4 defaults 1 2
UUID=496b4058-1c64-47e0-97f8-8760f41aaef8
swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
oproc /proc proc defaults 0 0
/dev/sda5 swap swap defaults 0 0
/dev/sda7 swap swap defaults 0
0
|
How
to remove the swap partition in Linux?
To remove the
swap partition use the following steps.
Deactivate the swap partition using a following
command.
#swapoff
<device name>
#swapoff
/dev/sda7
[root@linuxelearn
~]# swapoff /dev/sda7
[root@linuxelearn
~]#
|
- Remove the entery from the /etc/fstab
- Delete the partition through fdisk.
How
to increase swap into LVM Partition ?
Use the following steps to increase the Swap for LVM
- # swapoff -v /dev/kernalvg/swappart
- # lvm lvresize /dev/kernalvg/swappart -L +5G (increase from 5 GB to 10 GB)
- # mkswap /dev/kernalvg/swapvol
- # swapon -va
How
to remove or delete a Swap Partition for LVM
Use the following steps to delete/ remove the Swap
partition for LVM
- Step 1
swapoff -v
/dev/VG01/LV01
- Step 2
Then you need to delete the swap partition entirely.
#lvremove
/dev/VG01/LV01
- Step 3
Remove the following entry from your /etc/fstab
file.
sysfs /sys sysfs defaults 0 0
oproc /proc proc defaults 0 0
/dev/sda5 swap swap defaults 0 0
/dev/VG01/LV01 swap swap defaults 0
0
|
You Like to read this Also.....
- How to mount a partition in linux
- How to Change Permission of Files and Directories in Unix/Linux
- How to Assign IP Address in Unix or Linux / How to change IP Address in linux
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