Logical Volume Management (LVM) in Redhat Enterprise Linux (RHEL7/8)

February 19, 2021

Introduction to LVM: (Logical Volume Management)
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Problems with standard partitions:
There are some problems when working with hard disks and standard partitions. Consider a system with a small and a large hard disk device, partitioned like this. The first disk (/ dev/sda) is partitioned in two, the second disk (/dev/sdb) has two partitions and some empty space.
In the example above, consider the options when you want to enlarge the space available for /srv/project42. What can you do? The solution will always force you to unmount the file system, take a backup of the data, remove and recreate partitions, and then restore the data and remount the file system.

Solution with LVM:
Using LVM will create a virtual layer between the mounted file systems and the hardware devices. This virtual layer will allow for an administrator to enlarge a mounted file system in use. When LVM is properly used, then there is no need to unmount the file system to enlarge it.

Source: Paul Cobbaut EBook (http://linux-training.be/linuxsys.pdf)
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Command History: (Used in Video)

lsblk
fdisk -l
fdisk /dev/sdc
lsblk
pvcreate /dev/sdc1
vgcreate NewVolGrp /dev/sdc1
pvs
pvdisplay
vgs
vgdisplay
clear
lsblk
lvcreate -L -n NewLogVol NewVolGrp
lvcreate -L -n NewLogVol NewVolGrp
lvcreate -L 5G -n NewLogVol NewVol
lvremove NewLogVol
lvremove /dev/NewVolGrp/NewLogVol
clear
lvcreate -L 5G -n NewLogVol NewVol
lvs
lvdisplay
clear
lsblk
mkdir -p /NewDir
mount /dev/NewVolGrp/NewLogVol /Ne
umount /dev/NewVolGrp/NewLogVol
umount /NewDir/
df -h
lsblk
clear
mkfs.xfs /dev/NewVolGrp/NewLogVol
mount /dev/NewVolGrp/NewLogVol /Ne
umount /NewDir/
mount /dev/NewVolGrp/NewLogVol /Ne
df -h
vgs
lvextend -n /dev/NewVolGrp/NewLogV
lsblk
vgs
fdisk -l
fdisk /dev/sdc
lsblk
partprobe /dev/sdc
lsblk
pvcreate /dev/sdc2
vgextend NewVolGrp /dev/sdc2
vgs
lvextend -n /dev/NewVolGrp/NewLogV
lvs
xfs_growfs /dev/NewVolGrp/NewLogVo
df -hT

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