LVM-Logical-Volume-Manager

Creating hard drive space into logical volumes.
Since physical volumes cannot span over more than one drives.
/boot partition cannot be a lvm because the partition cannot be read by the boot loader
/boot should be on a separate partitions. - ext3
lvm2 uses the device mapper driver in the kernel 2.6
First create PV -physical volume, then create volume group-VG, and then the logical volume-LV.

How To Create LVM Logical Volume Manager And Work With With LVM

physical volumes = /dev/hdb1
volume groups= used to create logical volumes (example 'mydatavg')
logical volumes= (example /dev/mydatavg/myvol)

   In LVM, Volume Groups (VGs) are split up into logical volumes (LVs)

Check image at http://www.lea-linux.org/cached/printable=yes/index/Leapro-pro_sys-lvm.html

[root@galileo ~]# fdisk -l

   Disk /dev/sda: 80.0 GB, 80032038912 bytes
   255 heads, 63 sectors/track, 9730 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
   /dev/sda1   *           1          25      200781   83  Linux
   /dev/sda2              26         156     1052257+  82  Linux swap
   /dev/sda3             157        9730    76903155   83  Linux

initialize sda3 as a physical volume

  [root@galileo ~]# pvcreate /dev/sda3

pvcreate - initialize a disk or partition for use by LVM

For several disks

  [root@galileo ~]# pvcreate /dev/sdb
  [root@galileo ~]# pvcreate /dev/sdc

Once initialised the partitions, or drives, we will create a volume group.

  [root@galileo ~]#vgcreate mydatavg /dev/sda3

vgcreate - create a volume group

   Here "mydatavg" is the name of the volume group.

Single volume spanning two disks.

  [root@galileo ~]#vgcreate mydatavg /dev/sdb /dev/sdc

output of vgscan

  [root@galileo ~]# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "mydatavg" using metadata type lvm2

vgscan scans all SCSI, (E)IDE disks, multiple devices and a bunch of other disk devices in the system looking for LVM physical volumes and volume groups.
Create logical volumes which we can mount and actually use.

  [root@galileo ~]#lvcreate -n myvol --size 1g mydatavg

This command creates a volume of size 1Gb with the name myvol hosted on the LVM volume group mydatavg.

The logical volume will now be accessible via= /dev/mydatavg/myvol

Formatted and mounted just like any other partition.

  [root@galileo ~]# mkfs.ext3 /dev/mydatavg/myvol
  [root@galileo ~]# mkdir /home/lvmmount
  [root@galileo ~]# mount /dev/mydatavg/myvolt  /home/lvmmount

lvdisplay - display attributes of a logical volume

  [root@galileo ~]# lvdisplay

vgscan - scan all disks for volume groups and rebuild caches

How to Resize the volume= /dev/mydatavg/myvolt

  [root@galileo ~]# umount /home/lvmmount

    [root@galileo ~]#  lvextend -L+1g dev/mydatavg/myvolt

NAME

       lvextend - extend the size of a logical volume

  -L, --size [+]LogicalVolumeSize[kKmMgGtT]
              Extend  or  set  the  logical  volume  size in units in units of
              megabytes.

check lvdisplay again...but ext3 filesystem on it has stayed unchanged.
We need to resize the filesystem to actually fill the volume:

      [root@galileo ~]# e2fsck -f /dev/mydatavg/myvolt 

     -f     Force checking even if the file system seems clean.

      root@lappy:~# resize2fs /dev/mydatavg/myvolt

      resize2fs - ext2/ext3 file system resizer

How to Remove LVM

NAME

       lvremove - remove a logical volume

    [root@galileo ~]# lvremove /dev/mydatavg/myvolt

If partition is to be mounted at boot-time you should update your /etc/fstab

   /dev/mydatavg/myvolt    /home/lvmmount       ext3  noatime  0 2

Running pvdisplay will allow you to see which physical volume(s) make up your volume group.

Check /etc/lvm/ directory.