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