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Creating a LVM

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 

Removing a disk from a LVM

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
welcome/linux_usually/lvm.txt · Dernière modification: 2017/02/25 19:42 (modification externe)