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

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:
```
pvcreate /dev/sda10
pvcreate /dev/sdb1 
```
pvdisplay or pvscan to get info.
create the volume group “vgBackupPC”:
```
vgcreate vgBackupPC /dev/sda10 /dev/sdb1
```
vgdisplay to get info.
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.
create an ext4 file system on the logical volum:
```
mkfs -t ext4 /dev/vgBackupPC/lvBackupPC 
```

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
```