====== Creating a LVM ======

Source: [[https://doc.ubuntu-fr.org/lvm|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'' \\
  - if not present, create (with fdisk od gparted or...) the both partitions. \\ __**Be careful:**__all the data stored on these partition will be lost!
  - create the both physical volumes: <code>
pvcreate /dev/sda10
pvcreate /dev/sdb1 </code> ''pvdisplay'' or ''pvscan'' to get info.
  - create the volume group "vgBackupPC":<code>
vgcreate vgBackupPC /dev/sda10 /dev/sdb1</code> ''vgdisplay'' to get info.
  - create the logical volume "lvBackupPC" on the entire space of the volume group:<code>
lvcreate -n lvBackupPC -l 100%FREE vgBackupPC</code> ''lvdisplay'' to get info. \\  ''-n'' is to give the name and ''-l'' to deal with the storage space => see the man for more details.
  - create an ext4 file system on the logical volum:<code>
mkfs -t ext4 /dev/vgBackupPC/lvBackupPC </code>
  - mounting the LVM
    * with the name of the LVM <code>
mount -t ext4 /dev/vgBackupPC/lvBackupPC /mount/point </code>
    * 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: <code>
$ blkid
/dev/sda1: UUID=....
/dev/sda2: UUID=....
/dev/sda3: UUID=....
....
/dev/mapper/vgBackupPC-lvBackupPC: UUID="521489ca-ba67-49e9-a3c6-fa62b0eeeb2f" TYPE="ext4"</code>
    * mounting: <code>
mount -t ext4 UUID=521489ca-ba67-49e9-a3c6-fa62b0eeeb2f /mount/point </code>

====== 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: <code>
# 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 </code>
  * Check if there is enough place on the other physical volume to get sdb1 out of the LVM: <code>
# 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 </code> So only 287MB are used, so the volume /dev/sda8 can contain all the data.
  * Unmount the LVM <code># umount /mnt/dd_affa </code>
  * Reduce the size of the file system, a bit more that would be necessary the remove sdb1 => 1,1TB <code>
# lvresize --resizefs --size -1,1T /dev/mapper/vgBackupPC-lvBackupPC </code>
  * Empty sdb1 of the LVM (=transfer the data to the remaining volumes) <code># pvmove /dev/sdb1 </code>
  * Remove sdb1 from the LVM: <code># vgreduce vgBackupPC /dev/sdb1</code>
  * Delete the physical volume: <code># pvremove /dev/sdb1</code>
  * Grow the remaining file system of the LVM to the maximal size again: <code># resize2fs /dev/mapper/vgBackupPC-lvBackupPC</code>