01 : Non Root Disk For the external volume which doesn’t have the operating system just detach the volume and extend it then reattach again.
02: Root Disk But for OS root disk you will need to take a snapshot from the volume and recreate the instances from the created snapshot as per below steps.
- create a snapshot of the old instance volume.
- create a new volume from the created snapshot with required disk space .
- create a new instance from this new volume. Make sure to create the instance in the same volume availability zone.
If you want to use the same private and public IP addresses
- Disassociate the floating ip from the old instance.
- Detach the network interface card from both instances.
- using OpenStack CLI run
#nova interface-attach --net-id <net-ID> --fixed-ip <old-Private-IP> <New-Instance-ID>
- associate the old floating ip to the new instance.