Logical Volume Manager

Object of LVM

1) P.V   Physical Volume

2) V.G   Volume Group  (it could be from different HDD)

3) L.v   Logical Volume (it create in LVM)

I.

II.

III. All LVM become V.G   ( Volume Group)

     All LVM1,2 .... N become VG.

IV. L.M

From V.G we needs to create L.M 

P.E  ( Physical Extend )

Physical Volume P.V we will get P.E.

1 PE = 4 M.B. (Mega byte)

LV ---> LE

LE ----> Logical Extend

How to create LVM.

#fdisk /dev/sda

Create two Partition and change system id to 8e (Hexadecimal for LVM)

-> n

-> E

-> u

-> +500M

-> t 8e (repeat all step for 2^nd partition above command runs after

#fdisk /dev/sda 

# partprobe

# pvcreate /dev/sda? (? 1^st partition NO) /dev/sda?(?2^nd Partition)

# pvdisplay

# pvscan

( TO create physical Volume PV)

#vgcreate lvm0 /dev/sda? /dev/sda? (? 1^st & 2^nd Partition NO)

#vgscan

(TO create volume group)

#vgdisplay

#lvcreate –L +300M lvm0

(default name lvm0)

(to format the logical volume )

#mkfs.ext3  /dev/lvm0/lv010

#partprobe

#mkdir /lvm0

(Mount lvm0 in /lvm0 directory)

#mount /dev/lvm0/lv010 /lvm0

After reboot for auto mount add entry of this partition in /etc/fstab

Or add command with full path in /etc/rc.local.

To extend  LVM Partition

#lvextend –L +300M /dev/lvm0/lv010

#partprobe

To Reduce LVM Partition

Very Important small mistake lead you in big trouble so be very careful while reducing

The LVM Volume.

* It is mandatory to umount  your Volume before shirking/reducing the LVM Volume 

You have 5 GB Volume and you want to reduce it to 4 GB, There will be 4 GB Space reclaim from the Volume Group VG. and your final LV size will be 1 GB. 

# umount /oracle or # umount /dev/VolGroup00/lvol0 

# lvresize --resizefs --size -4G /dev/lvmtest/lvol0