Resizing Ephemeral Disk by Changing The Flavor of The Instance Does Not show Increased "/" Partition Size Inside The Instance.

Problem

Resizing ephemeral disk by changing the flavor of the Instance does not show Increased "/" partition size inside the Instance.

Environment

• Platform9 Managed OpenStack - All Versions
• CentOS
• Ubuntu

Answer

• If the instance is created with the below option, it will not format all the disk to the size defined in the flavor inside the instance. This option allows the disk inside the VM to be partitioned as per the configuration defined inside the Image at the time of image creation.

$ openstack server show [UUID] --fit-width -c name  -c OS-DCF:diskConfig +-------------------------------+-----------------------------------+| Field                         | Value                             |+-------------------------------+-----------------------------------+| OS-DCF:diskConfig             | MANUAL                            || OS-EXT-SRV-ATTR:instance_name | [instance name]                   |

• If the target flavor disk is larger, the remaining disk space is left unpartitioned. This enables images to manage the disk configuration manually.
• The available disk could be added to the "/" partition if it created on LVM, else it could be used to create a new partition.
• The other option is Auto which allows the disk to be completely utilized under the partitions defined in the image without specifying the partition size.

Additional Information

• Reference Links:
  • OpenStack Disk Image Builder
  • Cloud Init - Disk Partition Section