What is LVM?
LVM is a tool for logical volume management which includes allocating disks, striping, mirroring and resizing logical volumes. With LVM, a hard drive or set of hard drives is allocated to one or more physical volumes.
How to setup LVM in RHEL 7
Once the physical disk space has been made available to the host, run the following command to identify the disk location:
fdisk -l Disk /dev/sdb: 4294 MB, 4294967296 bytes, 8388608 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 Disk label type: dos Disk identifier: 0x5eee65f8
The output of the above command identifies the location of the 4 GB disk as being located in /dev/sdb. The next step involves issuing the following command (replace /dev/sdv with the output you receive from the above command):
[root@slave ~]# fdisk /dev/sdbTyp Type n to create a new partition and press enter three times until you reach the Last sector prompt. Enter +4GB here and press enter. Type in w and press enter to make the changes live. Issuing partprobe makes the partition live without rebooting the host.
[root@slave ~]# partprobe
The next step involves creating a physical volume.
[root@slave ~]# pvcreate /dev/sdb1 Physical volume "/dev/sdb1" successfully created
Run a pvscan to pickup the changes.
[root@slave ~]# pvscan PV /dev/sda2 VG rhel lvm2 [7.51 GiB / 0 free] Total: 1 [7.51 GiB] / in use: 1 [7.51 GiB] / in no VG: 0 [0 ]
We now need to create a volume group.
[root@slave ~]# vgcreate roldy /dev/sdb1 Volume group "roldy" successfully created
Inside of this volume group, we will now create a logical partition.
[root@slave ~]# lvcreate roldy --name snookicoco /dev/sdb1 -L 200MB Logical volume "snookicoco" created
Format the file system with xfs using the below command:
[root@slave ~]# mkfs.xfs /dev/roldy/snookicoco meta-data=/dev/roldy/snookicoco isize=256 agcount=4, agsize=12800 blks = sectsz=512 attr=2, projid32bit=1 = crc=0 data = bsize=4096 blocks=51200, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 ftype=0 log =internal log bsize=4096 blocks=853, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0
Create a folder on the host which will be mapped to this storage:
[root@slave ~]# mkdir /snookicoco
In order to edit the fstab, we will need to obtain the UUID of the volume. The UUID can be easily obtained via the blkid command.
[root@slave ~]# blkid /dev/sda1: UUID="46814065-a338-4860-a3f8-781b132987c6" TYPE="xfs" /dev/sda2: UUID="3gzDCV-lPFf-8hKA-Kojk-XI01-T7SR-xfK8fd" TYPE="LVM2_member" /dev/sdb1: UUID="QCrBPH-KPEw-PZ3c-xDs0-nUVE-esuL-AZorqV" TYPE="LVM2_member" /dev/mapper/rhel-root: UUID="dddea344-415f-4b2b-811f-8d7eac492f9e" TYPE="xfs" /dev/mapper/rhel-swap: UUID="e7128c41-27b0-45ad-8f20-ddf7ce444aa1" TYPE="swap" /dev/mapper/roldy-snookicoco: UUID="ae3cc85c-158f-4075-9025-5db0998c1d73" TYPE="xfs"
It’s now time to mount the partition using the fstab.
[root@slave ~]# vi /etc/fstab
Copy the UUID across to a new line in the fstab, add the local mount point and specify the file system as per the below entry:
# /etc/fstab # Created by anaconda on Thu Sep 18 00:41:01 2014 # # 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 # /dev/mapper/rhel-root / xfs defaults 1 1 UUID=46814065-a338-4860-a3f8-781b132987c6 /boot xfs defaults 1 2 /dev/mapper/rhel-swap swap swap defaults 0 0 UUID="ae3cc85c-158f-4075-9025-5db0998c1d73" /snookicoco xfs defaults 1 2 ~ ~
Verify that the mount point is now listed.
[root@slave ~]# df -hk | grep snookicoco /dev/mapper/roldy-snookicoco 201388 10400 190988 6% /snookicoco
How to extend a logical volume
Extending logical volumes is possible thanks to the lvextend utility.
lvextend -L +500M /dev/coco/chops
Fin.
Adventures in Unix Systems Administration 