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LVM-Logical-Volume-Manager-for-Linux-Kernel

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.

• Reference:

http://www.linuxconfig.org/Linux_lvm_-_Logical_Volume_Manager#This_is_what_we_are_going_to_do