How to Create and Manage LVM in CentOS
Steps to Manage and Create LVM Using vgcreate, lvcreate and lvextend Commands
Logical Volume Management is used for creating multiple logical volumes which means allocating disks space, mirroring and resize volumes in any method without any data loss. LFCS: To Manage and Create LVM Using vgcreate, lvcreate and lvextend Commands is explained in this article.
The structure of the LVM consists of
- Numerous logical volumes can be created in a volume group with the resize option.
- The volume group created is a single storage unit.
- One or more partition or hard disk is configured as physical volumes (PVs).
To Creating Physical Volumes, Volume Groups, and Logical Volumes
Run the following command to create physical volumes on /dev/sda5, /dev/sda6, and /dev/sda7:
[root@linuxhelp ~]# pvcreate /dev/sda5 /dev/sda6 /dev/sda7
Physical volume " /dev/sda5" successfully created
Physical volume " /dev/sda6" successfully created
Physical volume " /dev/sda7" successfully created
and to list the newly created PVs run the following
[root@linuxhelp ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda5 lvm2 a-- 3.00g 3.00g
/dev/sda6 lvm2 a-- 3.00g 3.00g
/dev/sda7 lvm2 a-- 3.00g 3.00g
To get detailed information about each PV use the following command.
[root@linuxhelp ~]# pvdisplay /dev/sda5
" /dev/sda5" is a new physical volume of " 3.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sda5
VG Name
PV Size 3.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID a0iS9I-ZFIi-bEU0-Jt08-hGu5-BJ4S-knR5ZQ
[root@linuxhelp ~]# pvdisplay /dev/sda6
" /dev/sda6" is a new physical volume of " 3.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sda6
VG Name
PV Size 3.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID Zv9U3D-iS2x-8vzk-XAS2-vdVa-j8s9-sXJe2i
[root@linuxhelp ~]# pvdisplay /dev/sda7
" /dev/sda7" is a new physical volume of " 3.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sda7
VG Name
PV Size 3.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID LX8D8N-KTUX-iNp8-bE6L-WSOP-Ledp-63SrbK
For generate volume group with the name vg1 using /dev/sda5 and /dev/sda6 use the following command.
[root@linuxhelp ~]# vgcreate vg1 /dev/sda5 /dev/sda6
Volume group " vg1" successfully created
Execute the following command to view the volume group information.
[root@linuxhelp ~]# vgdisplay vg1
--- Volume group ---
VG Name vg1
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 5.99 GiB
PE Size 4.00 MiB
Total PE 1534
Alloc PE / Size 0 / 0
Free PE / Size 1534 / 5.99 GiB
VG UUID NiC09Y-1mLt-k9Mj-gff6-ml0C-OZXO-r21gWX
As vg1 contains two 3 GB disks, a single 6 GB drive appears.
It is necessary to consider space while creating logical volumes.
Here, we have created two LV named lv1 and backup.
[root@linuxhelp ~]# lvcreate -L 3G -n lv1 vg1 Logical volume " lv1" created [root@linuxhelp ~]# lvcreate -l 100%FREE -n backup vg1 Logical volume " backup" created
Explanations
The option ' -n' shows the name of the Lv ' -L' is for size of the memory and ' -l' represents the remaining available space.
Run the following command to view the list of LV
[root@linuxhelp ~]# lvs
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
backup vg1 -wi-a----- 2.99g
lv1 vg1 -wi-a----- 3.00g
Use the following command to display the detailed information.
[root@linuxhelp ~]# lvdisplay
--- Logical volume ---
LV Path /dev/vg1/lv1
LV Name lv1
VG Name vg1
LV UUID IqgHAy-B4d0-CHOR-l6IE-q0cW-WRUm-o8W3Ep
LV Write Access read/write
LV Creation host, time linuxhelp, 2016-04-26 09:51:15 +0530
LV Status available
# open 0
LV Size 3.00 GiB
Current LE 768
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
--- Logical volume ---
LV Path /dev/vg1/backup
LV Name backup
VG Name vg1
LV UUID SHj1g4-cE1N-Suuo-4yo4-qdVC-vP3f-JUaMOm
LV Write Access read/write
LV Creation host, time linuxhelp, 2016-04-26 09:52:03 +0530
LV Status available
# open 0
LV Size 2.99 GiB
Current LE 766
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:1
Using mkfs command we are formatting /dev/vg1/lv1 and /dev/vg1/backup with ext4 file system.
[root@linuxhelp ~]# mkfs.ext4 /dev/vg1/lv1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
196608 inodes, 786432 blocks
39321 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=805306368
24 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
[root@linuxhelp ~]# mkfs.ext4 /dev/vg1/backup
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
196224 inodes, 784384 blocks
39219 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=803209216
24 block groups
32768 blocks per group, 32768 fragments per group
8176 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
To Resize the Logical Volumes and Extending Volume Groups
Run the following command to alter the memory space of one file and to another.
[root@linuxhelp ~]# lvreduce -L -1G -r /dev/vg1/lv1
fsck from util-linux 2.23.2
/dev/mapper/vg1-lv1: clean, 11/196608 files, 31036/786432 blocks
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/mapper/vg1-lv1 to 524288 (4k) blocks.
The filesystem on /dev/mapper/vg1-lv1 is now 524288 blocks long.
Reducing logical volume lv1 to 2.00 GiB
Logical volume lv1 successfully resized
[root@linuxhelp ~]# lvextend -l +100%FREE -r /dev/vg1/backup
fsck from util-linux 2.23.2
/dev/mapper/vg1-backup: clean, 11/196224 files, 31006/784384 blocks
Extending logical volume backup to 3.99 GiB
Logical volume backup successfully resized
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/mapper/vg1-backup to 1046528 (4k) blocks.
The filesystem on /dev/mapper/vg1-backup is now 1046528 blocks long.
don' t forget to include minus or plus while resizing the LV.
Use the following command to add /dev/sd7 to vg1,
[root@linuxhelp ~]# vgextend vg1 /dev/sda7
Volume group " vg1" successfully extended
To increase the size of the VG
Run the following command to increase the size of the VG.
[root@linuxhelp ~]# vgdisplay vg1
--- Volume group ---
VG Name vg1
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 6
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 0
Max PV 0
Cur PV 3
Act PV 3
VG Size 8.99 GiB
PE Size 4.00 MiB
Total PE 2301
Alloc PE / Size 1534 / 5.99 GiB
Free PE / Size 767 / 3.00 GiB
VG UUID NiC09Y-1mLt-k9Mj-gff6-ml0C-OZXO-r21gWX
To Mount Logical Volumes on Boot and on Demand
Run the following commands to create mount points.
[root@linuxhelp ~]# mkdir /mnt/backup
[root@linuxhelp ~]# mkdir /mnt/lv1
Run the following command on each disk to identify UUID.
[root@linuxhelp ~]# blkid /dev/vg1/backup /dev/vg1/backup: UUID=" 0fdf65b1-b15d-4c6f-9978-7feca1aa3577" TYPE=" ext4" [root@linuxhelp ~]# blkid /dev/vg1/lv1 /dev/vg1/lv1: UUID=" d4b8c7a4-6a9b-47c7-b14f-32cd427f370f" TYPE=" ext4"
Now we will make it as permanent mount by editing in /etc/fstab.
# # /etc/fstab # Created by anaconda on Sat Apr 23 10:58:25 2016 # # Accessible filesystems, by reference, are maintained under ' /dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # UUID=40821247-96e6-4735-9bf7-fd796042e3ac / xfs defaults 1 1 UUID=cfb663ce-ac90-4d4e-99d2-a7c1969c5d89 /boot xfs defaults 1 2 UUID=06aced7b-22e6-4910-b486-74369c27ebac swap swap defaults 0 0 UUID=0fdf65b1-b15d-4c6f-9978-7feca1aa3577 /mnt/backup ext4 defaults 0 0 UUID=d4b8c7a4-6a9b-47c7-b14f-32cd427f370f /mnt/lv1 ext4 defaults 0 0
Save and mount.
[root@linuxhelp ~]# mount -a
[root@linuxhelp ~]# mount | grep mnt
/dev/mapper/vg1-backup on /mnt/backup type ext4 (rw,relatime,seclabel,data=ordered)
/dev/mapper/vg1-lv1 on /mnt/lv1 type ext4 (rw,relatime,seclabel,data=ordered)
Q
What is Logical Volume Management?
A
Logical Volume Management is used for creating multiple logical volumes which means allocating disks space, mirroring and resize volumes in any method without any data loss.
Q
What is the command to mount all the partitions in Linux?
A
For mounting all the partitions use "mount -a" command.
Q
What is the command to list and see the UUID of the mounted disk?
A
Use "blkid partition path" to list and see the options.
Q
How to mount the partitions permanently after creating LVM?
A
Make an entry in "/etc/fstab" after LVM creation.
Q
What file system is available for centos/RHEL?
A
For RHEL/Centos 6 better use "xfs" but ext4 can also be used.