Create LVM logical volume

1. create a partition
# fdisk /dev/sdb
n > p > 3 > +100M
Change the partition type:
t > 3 > l (overview) > 8e (Linux LVM) > p (verify) > w
# partprobe – push the changes to kernel.
2. create the physical volume.
# pvcreate –help
# pvcreate /dev/sdb3
# pvs
Put it into Volume Group:
# vgcreate –help
# vgcreate vgmyvg /dev/sdb3
vgmyvg – this is volume group name which should be started with “vg”. Make it easy to find the volume group.
Volume group have 94MB. 4 MB are used for metadata.
3. create the logical volume from volume group:
# lvcreate –help | less
# lvcreate -n lvmylv -L 96M vgmyvg
-n is for name….is for see better
-L is required and is for size in M or G.
vgmyvg – is the name of volume group used for creation.
# lvs
Now I can put file system on it.
# mkfs.ext2 /dev/vgmyvg/lvmylv
Now mount it
# mount /dev/vgmyvg/lvmylv /mnt
Now check if the LVM volume has been mounted:
# mount | grep ^/dev
The mount is /dev/mapper/
Both /dev/vgmyvg/lvmylv and /dev/mapper/vgmyvg/lvmylv are pointing to same device: ../dm-3
This is the same device mapper used for creating luks and volumes.

Growing an LVM Logical volume
Can be resizable easy.
# df -h (disk free human readable format)
If the disk is full, must make the file system bigger.
check the volume group in order to see if there is some space available.
# lvs
Check VG for space available
# vgs
No disk free space available.
I have to make VG bigger by adding physical volume.
# fdick /dev/sdb
I have 3 partitions. There is room for one more:
Maybe I will have to add partitions in future. For that I will have to make an extended partition and inside this extended partition I will create logical partitions. In logical partitions I will use pv.
n > e (extended) > (extended partitions consume the all remaining space).
p to test
# n > +100M > t (type) > 8e (Linux LVM) > w
# partprobe
I will not create the PV. I’m starting direct to resize the volume group.
# vgextend –help
# vgextend vgmyvg /dev/sdb5
Check now:
# vgs
# lvextend –help
# lvextend -l +100%FREE -r /dev/vgmyvg/lvmylv
-l is used to use 100% of free space
-r is to resize the file system.
Check the file system
# df -h

Shrinking an LVM Logical Volume
Need a fs which support shrinking. NFS is not supporting shrinking. ext4 is supporting
# df -h
The /moredata is not used and is ok to shrink.
# mount | grep lvmmylv
Is using an ext4 file system.
Must unmount the file system.
umount /moredata
1. reduce file system.
Check the file system:
# e2fsck -f /dev/vgmyvg/lvmylv
and now can reduce it without issues
# man -k resize
# resize2fs /dev/vgmyvg/lvmylv 100M
2. reduce the Logical Volume
# lvreduce –help
# lvreduce -L 102400K /dev/vgmyvg/lvmylv
Press yes in order to accept.
Now I have to mount the filesystem:
# mount -a (I will mount all)

Another approach will be with lvreduce with “-r” option.
Unmount hte directory.
# umount /moredata
# lvreduce -L 50M -r /dev/vgmyvg/lvmylv
This command is doing all.
# mount -a
The volume group will be done later.
!!!!! -r is not working on all file systems.