Logical Volume Manager (LVM) is a device mapper target that provides logical volume management for the Linux kernel. LVM allows to create Logical Volumes from underlying Physical Hard Disks (Physiacal Volumes). Logical Volumes can be easily extended and shrunk according to the file system capacity demands.
LVM Objects:
Physical Volume (PV): underlying physical storage for LVM. These are most often physical hard disks, but also can be: partitions, RAID volumes, etc…
Volume Group (VG): storage pool, created from one or more Physical Volumes.
Physical Extent: small chunk of Physical Volume, used during Volume Group creation.
Logical Extent: mapped to Physical Extent, acting as front-end chunk for Logical Volumes.
Logical Volume: group of Logical Extents, used by the system as hard drive partition.
LVM Volume Group creation and Logical Volume creation is pretty simple:
1. Prepare hard disks for use with LVM
In this tutorial we will use two hard disks to create Physical Volumes for LVM: /dev/vdb, /dev/vdc.
Verify hard disks:
[root@tuxfixer ~]# fdisk -l /dev/vdb
Disk /dev/vdb: 2 GiB, 2147483648 bytes, 4194304 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
[root@tuxfixer ~]# fdisk -l /dev/vdc
Disk /dev/vdc: 3 GiB, 3221225472 bytes, 6291456 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytesCreate partition /dev/vdb1 on /dev/vdb device and set it’s file system type to: Linux LVM (hex code: 8e):
[root@wordpress ~]# fdisk /dev/vdb
Welcome to fdisk (util-linux 2.25.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x3d359b8e.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-4194303, default 2048): 2048
Last sector, +sectors or +size{K,M,G,T,P} (2048-4194303, default 4194303): 4194303
Created a new partition 1 of type 'Linux' and of size 2 GiB.
Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'.
Command (m for help): p
Disk /dev/vdb: 2 GiB, 2147483648 bytes, 4194304 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3d359b8e
Device Boot Start End Sectors Size Id Type
/dev/vdb1 2048 4194303 4192256 2G 8e Linux LVM
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.Create partition /dev/vdc1 on /dev/vdc device and set it’s file system type to: Linux LVM (hex code: 8e):
[root@tuxfixer ~]# fdisk /dev/vdc
Welcome to fdisk (util-linux 2.25.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x7537f08d.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-6291455, default 2048): 2048
Last sector, +sectors or +size{K,M,G,T,P} (2048-6291455, default 6291455): 6291455
Created a new partition 1 of type 'Linux' and of size 3 GiB.
Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'.
Command (m for help): p
Disk /dev/vdc: 3 GiB, 3221225472 bytes, 6291456 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7537f08d
Device Boot Start End Sectors Size Id Type
/dev/vdc1 2048 6291455 6289408 3G 8e Linux LVM
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.2. Create Physical Volumes
Create Physical Volumes from newly created partitions: /dev/vdb1, /dev/vdc1:
[root@tuxfixer ~]# pvcreate /dev/vdb1 /dev/vdc1
Physical volume "/dev/vdb1" successfully created
Physical volume "/dev/vdc1" successfully createdVerify Physical Volumes:
[root@tuxfixer ~]# pvdisplay /dev/vdb1
"/dev/vdb1" is a new physical volume of "2.00 GiB"
--- NEW Physical volume ---
PV Name /dev/vdb1
VG Name
PV Size 2.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID fdQ5Eq-KtkI-Wstd-pVvG-84jD-nJQw-rxDu4l
[root@tuxfixer ~]# pvdisplay /dev/vdc1
"/dev/vdc1" is a new physical volume of "3.00 GiB"
--- NEW Physical volume ---
PV Name /dev/vdc1
VG Name
PV Size 3.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID lf8Vwo-7Cz1-hAvD-IlYr-e7JF-jIJX-RN2A0X3. Create Volume Group
Let’s create Volume Group named VolGroup1 based on created Physical Volumes: /dev/vdb1, /dev/vdc1 using 2MiB sized chunks:
[root@tuxfixer ~]# vgcreate -s 2M VolGroup1 /dev/vdb1 /dev/vdc1
Volume group "VolGroup1" successfully createdNote: you can omit chunk size parameter (-s), then the Volume Group will be created using default chunk size of 4MiB
Verify newly created Volume Group:
[root@tuxfixer ~]# vgdisplay VolGroup1
--- Volume group ---
VG Name VolGroup1
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size 5.00 GiB
PE Size 2.00 MiB
Total PE 2558
Alloc PE / Size 0 / 0
Free PE / Size 2558 / 5.00 GiB
VG UUID MrFAHS-Un0z-bum3-k2Xg-uvPn-9Riw-w6ftolNote: pay attention to VG Size: 5GiB, it’s the sum of two Physical Volumes: /dev/vdb1, /dev/vdc1. Allocated Physical Extents equals zero (Alloc PE / Size: 0 / 0) and Free Physical Extents equals 5 GiB (Free PE / Size: 2558 / 5.00 GiB) because we haven’t created Logical Volumes yet and the Volume Group is empty.
4. Create Logical Volume
Create new 1GiB Logical Volume named LogVol1 in existing Volume Group VolGroup1:
[root@tuxfixer ~]# lvcreate -n LogVol1 -L 1G VolGroup1
Logical volume "LogVol1" created.Verify Logical Volume:
[root@tuxfixer ~]# lvdisplay /dev/VolGroup1/LogVol1
--- Logical volume ---
LV Path /dev/VolGroup1/LogVol1
LV Name LogVol1
VG Name VolGroup1
LV UUID w2M2x3-swgH-wku6-vsdM-DCIr-c2hw-82QvW0
LV Write Access read/write
LV Creation host, time wordpress, 2015-11-15 22:52:31 +0100
LV Status available
# open 0
LV Size 1.00 GiB
Current LE 512
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:25. Create file system on Logical Volume
Now we can format LogVol1 in order to be usable in the system, let’s use ext4 file system and label extra_volume:
[root@tuxfixer ~]# mkfs -t ext4 -L extra_volume /dev/VolGroup1/LogVol1
mke2fs 1.42.12 (29-Aug-2014)
Creating filesystem with 262144 4k blocks and 65536 inodes
Filesystem UUID: a375d652-eab4-4fa8-9efe-3113eca621fa
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: doneVerify newly created file system on LogVol1:
[root@tuxfixer ~]# blkid
/dev/vda1: UUID="1164d8f4-ae84-4451-be0f-210a6173989a" TYPE="ext4" PARTUUID="7583be5c-01"
/dev/vda2: UUID="3khed5-0vu0-66fV-VGA4-EC6G-eY0U-5HoThh" TYPE="LVM2_member" PARTUUID="7583be5c-02"
/dev/mapper/fedora-root: UUID="d2ca7304-551e-497d-8401-b54f72f11005" TYPE="ext4"
/dev/mapper/fedora-swap: UUID="c41b6f17-ece1-403e-b6d8-66b270db4e12" TYPE="swap"
/dev/vdb1: UUID="fdQ5Eq-KtkI-Wstd-pVvG-84jD-nJQw-rxDu4l" TYPE="LVM2_member" PARTUUID="3d359b8e-01"
/dev/vdc1: UUID="lf8Vwo-7Cz1-hAvD-IlYr-e7JF-jIJX-RN2A0X" TYPE="LVM2_member" PARTUUID="7537f08d-01"
/dev/mapper/VolGroup1-LogVol1: LABEL="extra_volume" UUID="a375d652-eab4-4fa8-9efe-3113eca621fa" TYPE="ext4"Note: our new LogVol1 is mapped by the system as device: /dev/mapper/VolGroup1-LogVol1
6. Create mount point and mount Logical Volume
Let’s create mount point for /dev/mapper/VolGroup1-LogVol1 in fstab, for example: /mnt. Edit /etc/fstab and add an entry at the bottom of the file:
[root@tuxfixer ~]# vim /etc/fstab/dev/mapper/fedora-root / ext4 defaults 1 1
UUID=1164d8f4-ae84-4451-be0f-210a6173989a /boot ext4 defaults 1 2
/dev/mapper/fedora-swap swap swap defaults 0 0
/dev/mapper/VolGroup1-LogVol1 /mnt ext4 defaults 1 2 Run mount -a to mount all the file systems in fstab, including /mnt on LogVol1:
[root@tuxfixer ~]# mount -aVerify mount point:
[root@tuxfixer ~]# df -hT
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 999M 0 999M 0% /dev
tmpfs tmpfs 1008M 72K 1008M 1% /dev/shm
tmpfs tmpfs 1008M 816K 1008M 1% /run
tmpfs tmpfs 1008M 0 1008M 0% /sys/fs/cgroup
/dev/mapper/fedora-root ext4 18G 3.3G 13G 21% /
tmpfs tmpfs 1008M 12K 1008M 1% /tmp
/dev/vda1 ext4 477M 122M 326M 28% /boot
tmpfs tmpfs 202M 8.0K 202M 1% /run/user/1000
/dev/mapper/VolGroup1-LogVol1 ext4 976M 1.3M 908M 1% /mntThat’s it, we have just created Volume Group and Logical Volume 🙂
7. Additional Logical Volumes and Volume Groups
After creating 1GiB LogVol1 on 5GiB VolGroup1 we still have about 4GiB of free space in VolGroup1 to use:
[root@tuxfixer ~]# vgdisplay VolGroup1
--- Volume group ---
VG Name VolGroup1
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 2
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 2
Act PV 2
VG Size 5.00 GiB
PE Size 2.00 MiB
Total PE 2558
Alloc PE / Size 512 / 1.00 GiB
Free PE / Size 2046 / 4.00 GiB
VG UUID MrFAHS-Un0z-bum3-k2Xg-uvPn-9Riw-w6ftolWe can use this free space to create more Logical Volumes (LogVol2, LogVol3, etc…) within VolGroup1 or even create new Volume Groups (VolGroup2, VolGroup3, etc…) using the same commands as we have used above. Free space can also be used to extend existing LogVol1.
