Tuncay Sahin

ICT Engineer | Docent ICT & Trainer

This document guides you through the steps for adding a new disk space to your Linux system or increasing an existing volume.

This is a “copy & paste” how-to. The easiest way to follow this tutorial is to use a command line SSH client (like putty) and simply copy and paste the commands (except where you have to provide your own information.

Adding a new disk

First add a new disk to your virtual machine within you virtualization environment.

 1 Get a list of your current disk/partition table.You can compare this output after adding the new disk.

fdisk -l

In the output you will find your current disk(s), for example something like:

Disk /dev/sda: 42.9 GB

 2 Re-scan the SCSI bus for the disk changes.

echo “- – -” > /sys/class/scsi_host/host0/scan
echo “- – -” > /sys/class/scsi_host/host1/scan
echo “- – -” > /sys/class/scsi_host/host2/scan
echo “- – -” > /sys/class/scsi_host/host3/scan
echo “- – -” > /sys/class/scsi_host/host4/scan

 3 Now get again the list of the disks/partition table. You will see the disk change(s) with its size.

fdisk -l

In the output you will find the added disk, for example something like:

Disk /dev/sda: 42.9 GB
Disk /dev/sdb: 32.2 GB

In case of a disk increasement, it can be that disk change is not updated, then run following command for the increased disk (sdb).

echo 1 > /sys/block/sdb/device/rescan

 4 Creating a new partition on the new disk, in this case, the disk is: /dev/sdb

fdisk /dev/sdb

you will get the message below:

Device contains neither a valid DOS partition table …

 5 Create a new partition

Type n to create a new partition

 6 Choose Primary partition

Type p to select primary

 7 Partition number.
Accept the default values for the other questions. Just press enter.

1 , this is the first partition on this disk

 8 Write table to disk and exit

Type w

 9 New partition now created, with PhysicalDevicePath:


 10 Initialize the new physical volume.

pvcreate /dev/sdb1


Physical volume “/dev/sdb1” successfully created

 11 Create a volume group on the physical volume. vgcreate VolumeGroupName PhysicalDevicePath

vgcreate vg_u01 /dev/sdb1


Volume group “vg_u01” successfully created

 12 Check the results by displaying physical volumes.


 13 Now create a (10 gigabyte) logical volume named LV_01 from the free extents in volume group VG_02

lvcreate -L 10G -n lv_u01 vg_u01



Logical volume “lv_u01” created

 14 List Logical Volumes path, needed for next step.


 15 Create a file system on the logical volume.

mkfs.ext4 /dev/vg_u01/lv_u01


Mounting the Logical Volume

 16 Create a mount folder

mkdir /u01

 17 Activating and Mounting the new Logical Volume.

mount /dev/vg_u01/lv_u01 /u01

 18 To mount the Logical Volume on system startup.

vi /etc/fstab

Insert following line:

/dev/vg_u01/lv_u01 /u01            ext4    defaults        1 1

 19 To get a list of your mounted Logical Volumes

df -h


Extending a Logical Volume

First increase the disk size of your virtual machine.
Then follow the same steps from above, adding a new disk,  until step 10. The only difference is:

Step 4. Create an additional partition on the existing disk. So you must use here the existing disk.
Step 7. Partition can’t be 1. After step 4, first type p to view the existing partition(s). Increase the number with  1.

Now follow the steps below to extend the Logical Volume:

 11 Get VG names needed for next step


 12 Extend the Volume Group to include the new physical volume

vgextend vg_u01 /dev/sdb2

 13 Get LV path needed for next step


 14 Extend the LogicalVolume with the available/remaining space. Or:

lvextend -l +100%FREE /dev/vg_u01/lv_u01

 15 extends the logical volumne /dev/myvg/homevol to (for example) 12 gigabytes. Or:

lvextend -L12G /dev/vg_u01/lv_u01

 16 adds (for example) 10 gigabyte to the logical volume  from the free extents in the volume group.

lvextend -L+10G /dev/vg_u01/lv_u01

 17 Resize the File system

resize2fs /dev/vg_u01/lv_u01

If you get the error below, first install e4fsprogs to support the ext4dev file system.

resize2fs: Filesystem has unsupported feature(s) while trying to open /dev/vg_u01/lv_u01
Couldn’t find valid filesystem superblock.

yum install e4fsprogs

resize4fs /dev/vg_u01/lv_u01

 18 Verify the results

df -h

Removing a Logical Volume

 1 A logical volume must be closed before it can be removed.

umount /dev/vg_u01/lv_u01

 2 Remove logical volume(s) from the system.

lvremove /dev/vg_u01/lv_u01

LVM Commands

Some other useful Logical Volume Management Commands:

lvdisplay Display information about a logical volume
lvmdiskscan List devices that may be used as physical volumes
lvreduce Reduce the size of a logical volume
lvrename Rename a logical volume
lvresize Resize a logical volume
lvs Display logical volumes
pvresize Resize physical volume(s)
pvck Check the consistency of physical volume(s)
pvdisplay Display various attributes of physical volume(s)
pvremove Remove LVM label(s) from physical volume(s)
vgdisplay Display volume group information
vgextend Add physical volumes to a volume group
vgmerge Merge volume groups
vgreduce Remove physical volume(s) from a volume group
vgremove Remove volume group(s)
vgrename Rename a volume group
vgsplit Move physical volumes into a new or existing volume group


Meer informatie

Voor meer informatie of voor een persoonlijk adviesgesprek kunt u altijd vrijblijvend contact met mij opnemen.