How to extend a partition with unallocated space CentOS 7

If you are running a virtual server and need to extend a disk you can resize a partition and volume group without rebooting the server. If done correctly this process is non destructive to existing data.

Assuming your disk is /dev/sda and standard RHEL/CentOS partitioning:

Extend partition

fdisk /dev/sda

Enter p to print your initial partition table.

Enter d (delete) followed by 2 to delete the existing partition definition (partition 1 is usually /boot and partition 2 is usually the root partition).

Enter n (new) followed by p (primary) followed by 2 to re-create partition number 2 and enter to accept the start block and enter again to accept the end block which is defaulted to the end of the disk.

Enter t (type) then 2 then 8e to change the new partition type to "Linux LVM".

Enter p to print your new partition table and make sure the start block matches what was in the initial partition table printed above.

Enter w to write the partition table to disk. You will see an error about device or resource busy which you can ignore.

Update kernel in-memory partition table

After changing your partition table, run the following command to update the kernel in-memory partition table:

partx -u /dev/sda

Resize physical volume

Use this command to resize the PV to recognize the extra space

pvresize /dev/sda2

Resize LV and filesystem

In this command centos is the PV, root is the LV and /dev/sda2 is the partition that was extended. Use pvs and lvs commands to see your physical and logical volume names if you don't know them. The -r option in this command resizes the filesystem appropriately so you don't have to call resize2fs or xfs_growfs separately.

lvextend -r centos/root /dev/vda2