Create Logical volume for swap

[root@demo ~]# fdisk -cu /dev/vda

Command (m for help): p

Disk /dev/vda: 6442 MB, 6442450944 bytes
16 heads, 63 sectors/track, 12483 cylinders, total 12582912 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 identifier: 0x0006fab8

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048      526335      262144   83  Linux
/dev/vda2          526336     9914367     4694016   8e  Linux LVM
/dev/vda3         9914368    12582911     1334272    5  Extended

Command (m for help): n
Command action
   l   logical (5 or over)
   p   primary partition (1-4)
l
First sector (9916416-12582911, default 9916416):
Using default value 9916416
Last sector, +sectors or +size{K,M,G} (9916416-12582911, default 12582911): +100M

Command (m for help): p

Disk /dev/vda: 6442 MB, 6442450944 bytes
16 heads, 63 sectors/track, 12483 cylinders, total 12582912 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 identifier: 0x0006fab8

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048      526335      262144   83  Linux
/dev/vda2          526336     9914367     4694016   8e  Linux LVM
/dev/vda3         9914368    12582911     1334272    5  Extended
/dev/vda5         9916416    10121215      102400   83  Linux

Command (m for help): t
Partition number (1-5): 5
Hex code (type L to list codes): 8e
Changed system type of partition 5 to 8e (Linux LVM)

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@demo ~]# partx -a /dev/vda
BLKPG: Device or resource busy
error adding partition 1
BLKPG: Device or resource busy
error adding partition 2
BLKPG: Device or resource busy
error adding partition 3
BLKPG: Device or resource busy
error adding partition 5

[root@demo ~]# pvcreate /dev/vda5
WARNING: swap signature detected on /dev/vda5. Wipe it? [y/n] y
  Wiping swap signature on /dev/vda5.
  Writing physical volume data to disk "/dev/vda5"
  Physical volume "/dev/vda5" successfully created

[root@demo ~]# vgcreate -s 4M swapgrp /dev/vda5
  Volume group "swapgrp" successfully created

[root@demo ~]# lvcreate -L 80M -n swap /dev/swapgrp
  Logical volume "swap" created

[root@demo ~]# mkswap /dev/swapgrp/swap 
mkswap: /dev/swapgrp/swap: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 81916 KiB
no label, UUID=a81559c0-9ddc-4771-b8b3-fa850de90846

[root@demo ~]# swapon /dev/swapgrp/swap 
[root@demo ~]# swapon -s
Filename Type Size Used Priority
/dev/dm-3                               partition 81912 0 -1
[root@demo ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           996        888        107          0         33        347
-/+ buffers/cache:        508        488
Swap:           79          0         79
[root@demo ~]# vim /etc/fstab
at the end add the device name
#################################################
/etc/fstab
# Created by anaconda on Sun Feb  2 08:09:32 2014
#
# 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/vgsrv-root  /                       ext4    defaults        1 1
UUID=245a990d-dd79-47d3-a1ef-68bb725c9a04 /boot                   ext4    defaults        1 2
/dev/mapper/vgsrv-home  /home                   ext4    defaults        1 2
/dev/mapper/vgsrv-swap  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
proc                  /proc          proc    defaults        0 0
/dev/swapgrp/swap      swap                    swap    defaults        0 0
############################################################################
[root@demo ~]# mount -a


DELETE SWAP

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

[root@demo ~]# swapoff /dev/swapgrp/swap

[root@demo ~]# lvremove /dev/swapgrp/swap
Do you really want to remove active logical volume swap? [y/n]: y
  Logical volume "swap" successfully removed

[root@demo ~]# vgremove /dev/swapgrp
  Volume group "swapgrp" successfully removed

[root@demo ~]# pvs
  PV         VG    Fmt  Attr PSize   PFree
  /dev/vda2  vgsrv lvm2 a--    4.47g 384.00m
  /dev/vda5        lvm2 a--  100.00m 100.00m

[root@demo~]# pvremove /dev/v
vcs          vcs4         vcsa1        vcsa5        vda2         vgsrv/
vcs1         vcs5         vcsa2        vcsa6        vda3        
vcs2         vcs6         vcsa3        vda          vda5        
vcs3         vcsa         vcsa4        vda1         vga_arbiter

[root@demo ~]# pvremove /dev/vda5
  Labels on physical volume "/dev/vda5" successfully wiped

[root@demo~]# pvs
  PV         VG    Fmt  Attr PSize PFree
  /dev/vda2  vgsrv lvm2 a--  4.47g 384.00m