May 20, 2024

How to add a new LVM volumes for full and partial disk usage

4 min read

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The Logical Volume Manager commands in Linux facilitate adding new disks and volumes to the operating system. It’s easy to do this on the fly without requiring downtime or rebooting; though, I always recommend making a full backup of all data on any existing volumes first as well as taking a snapshot of the virtual machine(s) involved.

There are two options when it comes to adding volumes:

  1. Adding the full disk capacity to an existing volume
  2. Splitting disk capacity among new volumes

In this article, I’ll explain how to achieve both.

Adding the full disk capacity to a new volume using LVM

To add a new volume using the entirety of the new disk capacity, the goal is to add a 10GB mount point called /repos in a new volume group called repos.

Many shops use VMware exclusively for their servers, so this scenario takes place in a vSphere environment, but the steps involved would be the same if a disk were added to a physical server.

1. Examine the disks present

Log into the server, sudo to elevated root privileges, then examine the disks present by running:

lsblk

Which returns:

NAME                   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT

sda                      8:0    0  200G  0 disk

├─sda1                   8:1    0    1G  0 part /boot

├─sda2                   8:2    0   49G  0 part

│ ├─rhel-root          253:0    0   20G  0 lvm  /

│ ├─rhel-swap          253:1    0    4G  0 lvm  [SWAP]

│ ├─rhel-home          253:3    0    1G  0 lvm  /home

│ ├─rhel-var           253:4    0   10G  0 lvm  /var

│ ├─rhel-var_log       253:5    0   20G  0 lvm  /var/log

│ ├─rhel-var_opt       253:6    0    3G  0 lvm  /var/opt

│ ├─rhel-var_tmp       253:7    0    3G  0 lvm  /var/tmp

│ ├─rhel-usr_local     253:8    0   10G  0 lvm  /usr/local

│ ├─rhel-var_log_audit 253:9    0 1012M  0 lvm  /var/log/audit

│ ├─rhel-opt           253:10   0   65G  0 lvm  /opt

│ ├─rhel-opt_fireeye   253:11   0    2G  0 lvm  /opt/fireeye

│ ├─rhel-besclient     253:12   0    8G  0 lvm  /var/opt/BESClient

│ ├─rhel-opt_encase    253:13   0    2G  0 lvm  /opt/encase

│ └─rhel-tmp           253:14   0   15G  0 lvm  /tmp

sdb                      8:16   0  850G  0 disk

└─appvg-vaplv          253:2    0  850G  0 lvm  /opt/vap

2. Add a new disk via the vSphere console

Next, log into the vSphere console to add a new disk via these steps:

  • Right-click the VM.
  • Choose Edit Settings.
  • Choose Add New Device.
  • Choose Hard Disk.
  • Add the new disk using the desired size specifications (for the purpose of this article, I chose to add a 10GB disk).

Before moving on, run partprobe on the host for good measure to ensure the new disk was found.

3. Examine the disks present again to view the new hard disk

Run lsblk again, which will return:

NAME                   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT

sda                      8:0    0  200G  0 disk

├─sda1                   8:1    0    1G  0 part /boot

├─sda2                   8:2    0   49G  0 part

│ ├─rhel-root          253:0    0   20G  0 lvm  /

│ ├─rhel-swap          253:1    0    4G  0 lvm  [SWAP]

│ ├─rhel-home          253:3    0    1G  0 lvm  /home

│ ├─rhel-var           253:4    0   10G  0 lvm  /var

│ ├─rhel-var_log       253:5    0   20G  0 lvm  /var/log

│ ├─rhel-var_opt       253:6    0    3G  0 lvm  /var/opt

│ ├─rhel-var_tmp       253:7    0    3G  0 lvm  /var/tmp

│ ├─rhel-usr_local     253:8    0   10G  0 lvm  /usr/local

│ ├─rhel-var_log_audit 253:9    0 1012M  0 lvm  /var/log/audit

│ ├─rhel-opt           253:10   0   65G  0 lvm  /opt

│ ├─rhel-opt_fireeye   253:11   0    2G  0 lvm  /opt/fireeye

│ ├─rhel-besclient     253:12   0    8G  0 lvm  /var/opt/BESClient

│ ├─rhel-opt_encase    253:13   0    2G  0 lvm  /opt/encase

│ └─rhel-tmp           253:14   0   15G  0 lvm  /tmp

sdb                      8:16   0  850G  0 disk

└─appvg-vaplv          253:2    0  850G  0 lvm  /opt/vap

sdc                      8:32   0   10G  0 disk

In these results, we see the new 10GB disk added as sdc.

 4. Add a primary partition to the new hard disk

Run fdisk to add a primary partition to the disk, so the file system would recognize it. This step includes several commands:

fdisk -u -c /dev/sdc

This will return this message:

Welcome to fdisk (util-linux 2.23.2).

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

Building a new DOS disklabel with disk identifier 0xf9417ab7.

Command (m for help):

From here, there are six steps:

  1. Press n to create a new partition. This returns:

Partition type:

p   primary (0 primary, 0 extended, 4 free)

e   extended

Select (default p):

  1. Press p to create a primary partition. This returns:

Partition number

(1-4, default 1):

  1. Hit enter to accept the default of 1. This returns:

First sector (2048-20971519, default 2048):

  1. Hit enter to accept the default of 2048. This returns:

Using default value 2048

Last sector, +sectors or +sizeK,M,G (2048-20971519, default 20971519):

  1. Hit enter to accept the default of 20971519. This returns:

Using default value 20971519

Partition 1 of type Linux and of size 10 GiB is set

Command (m for help):

  1. Press w to write the changes. If successful, this returns:

The partition table has been altered!

Calling ioctl() to re-read partition table.

Syncing disks.

You’ll then want to create the /repos directory by running:

mkdir /repos

5. Create the physical and logical volumes from the new partition

The next step is to create the physical volume from the new partition by running:

pvcreate /dev/sdc1

This command will return:

Physical volume "/dev/sdc1" successfully created.

To create the new volume group, run:

vgcreate repos /dev/sdc1

This command will return:

Volume group "repos" successfully created.

Running vgs confirms the addition of 10GB volume group with this message:

VG    #PV #LV #SN Attr   VSize    VFree

appvg   1   1   0 wz--n- <850.00g     0

repos    3  14   0 wz--n- <208.99g 10.00g

You’ll want to create the logical volume (lv_repos) next:

lvcreate /n lv_repos -size 10G repos

A successful command returns:

Logical volume "repos" created

Then, create an ext3 file system for this logical volume with the command:

mkfs.ext3 /dev/repos/lv_repos

Which returns a notification that the file system has been successfully created.

6. Mount the new file system

To mount the new file system, run the command:

mount /dev/repos/lv_repos /repos

Ensure this file system will automatically mount the next time the server is rebooted by adding the following entry to /etc/fstab:

/dev/repos/lv_repos        /repos                ext4 defaults    0 0

Splitting the full disk capacity among multiple volumes

We will create two logical volumes called repos1 and repos2, each totaling 5GB.

First, follow steps 1–4 as shown above for adding the full disk capacity to a new volume. Then, create the /repos1 and /repos2 directories.

To do so, you’ll want to create the logical volumes using only the desired amount of space; in this case just 5GB:

lvcreate -n repo1 -size 5G repos

This returns:

Logical volume "repo1" created

For the second logical volume:

lvcreate -n repo2 -size 5G repos

This returns:

Volume group "repos" has insufficient free space (1279 extents): 1280 required.

As it turns out, you have to account for a slight bit of overhead in terms of disk space allocated to the first logical volume; it’s actually about 5.1GB used.

To account for this, run:

lvcreate -n repo2 -size 4.9G repos

Which returns:

Logical volume "repo2" created.

Close enough.

Then, run lvs to confirm the logical volumes:

LV                 VG Attr   LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert

repo1              repos  -wi-a-----   5.00g

repo2              repos  -wi-a-----   4.90g

Learn more about LVM

Working with LVM to perform disk and volume operations is quick, easy and reliable. I have performed on-the-fly disk management actions and never once experienced a technical issue much less an operating system crash or data loss.

For more information on LVM, check out the Complete Beginners Guide to LVM by linuxhandbook.com.

Read next: How to expand and shrink LVM volumes (TechRepublic)

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Source link Creating Logical Volume Management (LVM) is a great way to manage disk usage on a Linux system. With LVM, you can dynamically add additional storage to a system by creating new logical volumes during runtime. This is especially useful when dealing with limited disk space or when adding a new disk. In this article, we’ll explain how to add LVM volumes for full and partial disk usage.

First, let’s look at how to add a new LVM volume for full disk usage. The first step is to create a partition table on the disk. To do this, use the fdisk command. For example, if the new disk is sdc, type fdisk /dev/sdc. This will bring up a dialog where you can create a new partition table. Once the partition table is created, create the physical volume by entering pvcreate /dev/sdc1 (or whichever partition you created).

Next, you’ll need to create a Volume Group (VG). Enter vgcreate vg_name /dev/sdc1. Where vg_name is the name of your Volume Group. Once the VG is created, you can create the logical volume, lvcreate -L /dev/vg_name/lv_name. Where lv_name is the name of your logical volume.

For partial disk usage, it’s a bit trickier. First, you’ll need to create a partition on the disk for the LVM. Use the same fdisk command as before and create the partition table. You’ll also need to create a physical volume with pvcreate /dev/sdc1 or whichever partition number you created.

Next, you’ll need to determine the size of the logical volume you want to create. To do that, use the lvcreate command with the -L option and specify the desired size. For example, you can use lvcreate -L 2G /dev/vg_name/lv_name to create a 2GB logical volume.

Once the logical volume is created, you’ll need to format the new volume with a filesystem. To do this, use the mkfs command. For example, to format the new volume with ext4, you would use mkfs -t ext4 /dev/vg_name/lv_name.

Finally, you can mount the new logical volume using the mount command. To do this, use the following syntax: mount -t ext4 /dev/vg_name/lv_name /mount/point. Where /mount/point is the directory to which the volume will be mounted.

In summary, creating LVM volumes is a great way to manage disk usage on a Linux system. By following the steps discussed in this article, you can easily add a new LVM volume for full or partial disk usage. With LVM, you can manage your disk space more efficiently and grow your disks as needed.