Source: doc Ubuntu-fr - LVM

In this example we will create a LVM placed on 2 partitions: sda10 and sdb1
All the command are done with root permissions ⇒ su or sudo

1. if not present, create (with fdisk od gparted or…) the both partitions.
   Be careful:all the data stored on these partition will be lost!
2. create the both physical volumes:

   pvcreate /dev/sda10
   pvcreate /dev/sdb1 

   pvdisplay or pvscan to get info.

3. create the volume group “vgBackupPC”:

   vgcreate vgBackupPC /dev/sda10 /dev/sdb1

   vgdisplay to get info.

4. create the logical volume “lvBackupPC” on the entire space of the volume group:

   lvcreate -n lvBackupPC -l 100%FREE vgBackupPC

   lvdisplay to get info.
   -n is to give the name and -l to deal with the storage space ⇒ see the man for more details.

5. create an ext4 file system on the logical volum:

   mkfs -t ext4 /dev/vgBackupPC/lvBackupPC 

6. mounting the LVM
   • with the name of the LVM

     mount -t ext4 /dev/vgBackupPC/lvBackupPC /mount/point 

   • with the UUID
     This is a little bit tricky: the UUID to be used is NOT the UUID of the LV given by lvdisplay!
     For the mounting, we have to use the UUID of the file system:
     • getting the UUID of the file system:

       $ blkid
       /dev/sda1: UUID=....
       /dev/sda2: UUID=....
       /dev/sda3: UUID=....
       ....
       /dev/mapper/vgBackupPC-lvBackupPC: UUID="521489ca-ba67-49e9-a3c6-fa62b0eeeb2f" TYPE="ext4"

   • mounting:

     mount -t ext4 UUID=521489ca-ba67-49e9-a3c6-fa62b0eeeb2f /mount/point 

In this example we want to remove the disk (= the physical volume more exactly) dev/sdb1 from the LVM.

• Have a look at the general situation:

  # pvs -o+pv_used
    PV         VG         Fmt  Attr PSize   PFree Used   
    /dev/sda8  vgBackupPC lvm2 a--  363,51g    0  363,51g
    /dev/sdb1  vgBackupPC lvm2 a--  931,51g    0  931,51g 

• Check if there is enough place on the other physical volume to get sdb1 out of the LVM:

  # df -h /mnt/dd_affa/
  Sys. de fichiers                  Taille Utilisé Dispo Uti% Monté sur
  /dev/mapper/vgBackupPC-lvBackupPC   1,3T    287M  1,2T   1% /mnt/dd_affa 

  So only 287MB are used, so the volume /dev/sda8 can contain all the data.

• Unmount the LVM

  # umount /mnt/dd_affa 

• Reduce the size of the file system, a bit more that would be necessary the remove sdb1 ⇒ 1,1TB

  # lvresize --resizefs --size -1,1T /dev/mapper/vgBackupPC-lvBackupPC 

• Empty sdb1 of the LVM (=transfer the data to the remaining volumes)

  # pvmove /dev/sdb1 

• Remove sdb1 from the LVM:

  # vgreduce vgBackupPC /dev/sdb1

• Delete the physical volume:

  # pvremove /dev/sdb1

• Grow the remaining file system of the LVM to the maximal size again:

  # resize2fs /dev/mapper/vgBackupPC-lvBackupPC