Create LVMs using fdisk
Logical Volume Groups
A Logical Volume Group (LVM) is a way to aggregate multiple physical disks into a single, contiguous space, which can then be divided into logical volumes. This abstraction allows for more flexible disk management by enabling dynamic resizing of file systems, making it easier to expand or contract the available space as needed.
Using an LVM means you can combine several smaller disks into one larger volume, simplifying storage management. This approach is especially useful in environments where disk usage patterns are unpredictable, as it allows for seamless scaling of storage capacity without the need for significant reconfiguration.
Install and enable LVM
It's possible that when you run pvdisplay or any of the LVM commands for the first time, you may see an error message saying that the command is not found. LVM should come as default in most RHEL installation but in some cases, you may need to install the package separately.
First, verify if the package exists in your system:
rpm -qa |grep -i lvm
To install the LVM packages:
yum install lvm2*
Verify again:
$ sudo rpm -qa |grep -i lvm
lvm2-2.03.12-10.el8.x86_64
lvm2-dbusd-2.03.12-10.el8.noarch
lvm2-lockd-2.03.12-10.el8.x86_64
lvm2-libs-2.03.12-10.el8.x86_64
Check the version:
$ sudo lvm version
LVM version: 2.03.12(2)-RHEL8 (2021-05-19)
Library version: 1.02.177-RHEL8 (2021-05-19)
Driver version: 4.43.0
To see the LVM commands, use help:
$ lvm help
WARNING: Running as a non-root user. Functionality may be unavailable.
Available lvm commands:
Use 'lvm help <command>' for more information
config Display and manipulate configuration information
devtypes Display recognised built-in block device types
dumpconfig Display and manipulate configuration information
*output omitted.
Creating LVMs using fdisk
Outline:
- Create partitions
- Instead of writing immediately, we specify the type as LVM
- Write and save.
- Repeat steps 1-3 for other disks that will belong to the same group.
- Create the LV assembly using
pvcreate - Create the volume group using
vgcreate - Create the logical volume group using
lvcreate - Format the LV group using
mkfs - Mount the LV group to a using
mount
Lab Setup
In this section, we deleted all the partitions in all our three existing secondary disks from the previous labs.
$ sudo fdisk -l
Disk /dev/xvda: 10 GiB, 10737418240 bytes, 20971520 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: gpt
Disk identifier: F34B923A-6CE9-4CEF-841E-82EC5D63653C
Disk /dev/xvdd: 100 GiB, 107374182400 bytes, 209715200 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 /dev/xvdc: 100 GiB, 107374182400 bytes, 209715200 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 /dev/xvdb: 100 GiB, 107374182400 bytes, 209715200 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
None of the disks are mounted.
$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 7.7G 0 7.7G 0% /dev
tmpfs 7.8G 0 7.8G 0% /dev/shm
tmpfs 7.8G 17M 7.8G 1% /run
tmpfs 7.8G 0 7.8G 0% /sys/fs/cgroup
/dev/xvda2 10G 2.8G 7.3G 28% /
tmpfs 1.6G 0 1.6G 0% /run/user/1000
Create the partitions
First, we need to create partitions on the physical disks. This step is crucial because the partitions will be used to create the physical volumes for the LVM.
$ sudo fdisk /dev/xvdb
Welcome to fdisk (util-linux 2.32.1).
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 0xa782f8bf.
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):
First sector (2048-209715199, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-209715199, default 209715199):
Created a new partition 1 of type 'Linux' and of size 100 GiB.
Next, change the type from Linux to Linux LVM. Enter `t' to view all the available types.
Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): L
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 39 Plan 9 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 3c PartitionMagic 84 OS/2 hidden or c6 DRDOS/sec (FAT-
4 FAT16 <32M 40 Venix 80286 85 Linux extended c7 Syrinx
5 Extended 41 PPC PReP Boot 86 NTFS volume set da Non-FS data
6 FAT16 42 SFS 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS/exFAT 4d QNX4.x 88 Linux plaintext de Dell Utility
8 AIX 4e QNX4.x 2nd part 8e Linux LVM df BootIt
9 AIX bootable 4f QNX4.x 3rd part 93 Amoeba e1 DOS access
a OS/2 Boot Manag 50 OnTrack DM 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 51 OnTrack DM6 Aux 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 52 CP/M a0 IBM Thinkpad hi ea Rufus alignment
e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD eb BeOS fs
f W95 Ext'd (LBA) 54 OnTrackDM6 a6 OpenBSD ee GPT
10 OPUS 55 EZ-Drive a7 NeXTSTEP ef EFI (FAT-12/16/
11 Hidden FAT12 56 Golden Bow a8 Darwin UFS f0 Linux/PA-RISC b
12 Compaq diagnost 5c Priam Edisk a9 NetBSD f1 SpeedStor
14 Hidden FAT16 <3 61 SpeedStor ab Darwin boot f4 SpeedStor
16 Hidden FAT16 63 GNU HURD or Sys af HFS / HFS+ f2 DOS secondary
17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fb VMware VMFS
18 AST SmartSleep 65 Novell Netware b8 BSDI swap fc VMware VMKCORE
1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid fd Linux raid auto
1c Hidden W95 FAT3 75 PC/IX bc Acronis FAT32 L fe LANstep
1e Hidden W95 FAT1 80 Old Minix be Solaris boot ff BBT
We need to use the Linux LVM, which is 8e.
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'.
Verify and write:
Command (m for help): v
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
We can verify the configuration by printing the details:
Command (m for help): p
Disk /dev/xvdb: 100 GiB, 107374182400 bytes, 209715200 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: 0xa782f8bf
Device Boot Start End Sectors Size Id Type
/dev/xvdb1 2048 209715199 209713152 100G 8e Linux LVM
Repeat steps for other disks that will belong in the same LVM.
$ sudo fdisk /dev/xvdc
Welcome to fdisk (util-linux 2.32.1).
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 0xf52b87f4.
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):
First sector (2048-209715199, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-209715199, default 209715199):
Created a new partition 1 of type 'Linux' and of size 100 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): v
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
$ sudo fdisk /dev/xvdd
Welcome to fdisk (util-linux 2.32.1).
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 0xea43c836.
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):
First sector (2048-209715199, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-209715199, default 209715199):
Created a new partition 1 of type 'Linux' and of size 100 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): v
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Checking the disks again:
sudo fdisk -l
We;ll get the following output:
Disk /dev/xvda: 10 GiB, 10737418240 bytes, 20971520 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: gpt
Disk identifier: F34B923A-6CE9-4CEF-841E-82EC5D63653C
Device Start End Sectors Size Type
/dev/xvda1 2048 4095 2048 1M BIOS boot
/dev/xvda2 4096 20971486 20967391 10G Linux filesystem
Disk /dev/xvdd: 100 GiB, 107374182400 bytes, 209715200 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: 0xea43c836
Device Boot Start End Sectors Size Id Type
/dev/xvdd1 2048 209715199 209713152 100G 8e Linux LVM
Disk /dev/xvdc: 100 GiB, 107374182400 bytes, 209715200 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: 0xf52b87f4
Device Boot Start End Sectors Size Id Type
/dev/xvdc1 2048 209715199 209713152 100G 8e Linux LVM
Disk /dev/xvdb: 100 GiB, 107374182400 bytes, 209715200 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: 0xa782f8bf
Device Boot Start End Sectors Size Id Type
/dev/xvdb1 2048 209715199 209713152 100G 8e Linux LVM
Create the LV assembly (pvcreate)
Next, use pvcreate to initialize the partitions as physical volumes. This step prepares the partitions to be added to the volume group.
$ sudo pvcreate /dev/xvdb1 /dev/xvdc1 /dev/xvdd1
Physical volume "/dev/xvdb1" successfully created.
Physical volume "/dev/xvdc1" successfully created.
Physical volume "/dev/xvdd1" successfully created.
To do the reverse, we can also remove the assembly if in case we make a mistake. Just make sure that when you add them as a group, you will need to remove them as a group too.
$ sudo pvremove /dev/xvdb1 /dev/xvdc1 /dev/xvdd1
Labels on physical volume "/dev/xvdb1" successfully wiped.
Labels on physical volume "/dev/xvdc1" successfully wiped.
Labels on physical volume "/dev/xvdd1" successfully wiped.
To continue with the lab, we just need to create the assumble again by running the pvcreate command. After that, we can see the details by running the pvdisplay:
sudo pvdisplay
It will return the following output:
"/dev/xvdb1" is a new physical volume of "<100.00 GiB"
--- NEW Physical volume ---
PV Name /dev/xvdb1
VG Name
PV Size <100.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID tlF3vP-hBAU-MLCK-a8FR-v011-XEtS-W1Rinf
"/dev/xvdc1" is a new physical volume of "<100.00 GiB"
--- NEW Physical volume ---
PV Name /dev/xvdc1
VG Name
PV Size <100.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID UCkQXp-cLeP-VhyZ-Xu9z-CT8y-Zvhn-zNUR5u
"/dev/xvdd1" is a new physical volume of "<100.00 GiB"
--- NEW Physical volume ---
PV Name /dev/xvdd1
VG Name
PV Size <100.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID neHZec-iU6u-mLvA-GNVB-c4aW-l9MK-Q2cbeK
Create the volume group (vgcreate)
Here, we create the volume group using vgcreate and include the disks we want. As a best practice, we will add disks B and C to the group and leave disk D for future use. This allows for easier expansion of the volume group later if needed.
$ sudo vgcreate my-volumes /dev/xvdb1 /dev/xvdc1
Volume group "my-volumes" successfully created
If we check the single volume group, we can see that we were able to combine both 100GB storages into a single volume.
$ sudo vgdisplay
--- Volume group ---
VG Name my-volumes
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 199.99 GiB
PE Size 4.00 MiB
Total PE 51198
Alloc PE / Size 0 / 0
Free PE / Size 51198 / 199.99 GiB
VG UUID 1ngVdd-6f9x-Cv7Y-Xa1R-vK7u-z02e-kzBIs8
To read all physical volumes and determine if logical volume groups exist within those physical volumes:
$ sudo vgscan
Found volume group "my-volumes" using metadata type lvm2
To rename a volume group:
$ sudo vgrename my-volumes my-volumes-newname
Volume group "my-volumes" successfully renamed to "my-volumes-newname"
Create the LVM (lvcreate)
Finally, use lvcreate to create logical volumes within the volume group. Logical volumes can be resized as needed, providing flexibility in managing disk space.
$ sudo lvcreate --name group1 --size 99G my-volumes-newname
Logical volume "group1" created.
To show detailed information about all logical volumes in the system:
$ sudo lvdisplay
--- Logical volume ---
LV Path /dev/my-volumes-newname/group1
LV Name group1
VG Name my-volumes-newname
LV UUID FyzEp5-LFr8-A6xD-6aju-EPKq-W3V0-LUBRfR
LV Write Access read/write
LV Creation host, time tst-rhel, 2021-12-06 13:15:50 +0800
LV Status available
# open 0
LV Size 99.00 GiB
Current LE 25344
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
To identify available logical volumes and their associated volume groups:
$ sudo lvscan
ACTIVE '/dev/my-volumes-newname/group1' [99.00 GiB] inherit
Format the LV group (mkfs)
After creating the LV group, we need to format it using a filesystem so that the volume becomes usable.
$ sudo mkfs -t ext3 /dev/my-volumes-newname/group1
mke2fs 1.45.6 (20-Mar-2020)
Creating filesystem with 25952256 4k blocks and 6488064 inodes
Filesystem UUID: 5c9864ff-76a0-4c8d-9982-141cb54483e7
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872
Allocating group tables: done
Writing inode tables: done
Creating journal (131072 blocks): done
Writing superblocks and filesystem accounting information: done
Mount the LV group
To use the logical volume, you need to mount it. First, navigate to the /mnt directory and create a new directory where the logical volume group will be mounted. Then, proceed with the mounting process.
eden@tst-rhel:mnt $ sudo mkdir disklvm
eden@tst-rhel:mnt $ ll
total 0
drwxr-xr-x. 2 root root 6 Dec 6 06:08 diskb1
drwxr-xr-x. 2 root root 6 Dec 6 06:26 diskc1
drwxr-xr-x. 2 root root 6 Dec 6 06:26 diskc2
drwxr-xr-x. 2 root root 6 Dec 6 06:26 diskc3
drwxr-xr-x. 2 root root 6 Dec 6 13:26 disklvm
sudo mount -t ext3 /dev/my-volumes-newname/group1 /mnt/disklvm
Verify that the logical volume group has been successfully mounted by checking the mounted filesystems:
eden@tst-rhel:mnt $ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 7.7G 0 7.7G 0% /dev
tmpfs 7.8G 0 7.8G 0% /dev/shm
tmpfs 7.8G 17M 7.8G 1% /run
tmpfs 7.8G 0 7.8G 0% /sys/fs/cgroup
/dev/xvda2 10G 2.8G 7.3G 28% /
tmpfs 1.6G 0 1.6G 0% /run/user/1000
/dev/mapper/my--volumes--newname-group1 97G 61M 92G 1% /mnt/disklvm
I decided to rename the VG to myvolumes and LV to myvolumes to make it easier to type.
eden@tst-rhel:mnt $ sudo vgscan
Found volume group "my-volumes-newname" using metadata type lvm2
eden@tst-rhel:mnt $ sudo vgrename my-volumes-newname myvolumes
Volume group "my-volumes-newname" successfully renamed to "myvolumes"
Next, unmount the logical volume group:
eden@tst-rhel:mnt $ sudo umount disklvm
Rescan the volume groups and logical volumes to confirm the changes:
eden@tst-rhel:mnt $ sudo vgscan
Found volume group "myvolumes" using metadata type lvm2
eden@tst-rhel:mnt $ sudo lvscan
ACTIVE '/dev/myvolumes/group1' [99.00 GiB] inherit
Finally, mount the renamed logical volume group:
eden@tst-rhel:mnt $ sudo mount -t ext3 /dev/myvolumes/group1 /mnt/disklvm
Verify once again that the logical volume group has been successfully mounted:
eden@tst-rhel:mnt $ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 7.7G 0 7.7G 0% /dev
tmpfs 7.8G 0 7.8G 0% /dev/shm
tmpfs 7.8G 17M 7.8G 1% /run
tmpfs 7.8G 0 7.8G 0% /sys/fs/cgroup
/dev/xvda2 10G 2.8G 7.3G 28% /
tmpfs 1.6G 0 1.6G 0% /run/user/1000
/dev/mapper/myvolumes-group1 97G 61M 92G 1% /mnt/disklvm