.. _compute_inst_root_storage_increase_card:

Instance: root disk resize
==========================

Users are able to resize autonomously the root volume of their virtual machines.

.. important::

    It is allowed only to increase the quota of the root disk.

The procedure differs wether the VM is ephemeral or created from a bootable volume (more info on the :ref:`cloud/os_overview/os_components/compute:compute` page).

.. important::

  Before the procedure is advised to **shut down** the VM and detatch any secondary volumes.

First of all, disassociate, if present, the floating IP from the VM (do not release it otherwise it will be lost).

.. warning::
    If the floating IP is also released, it will be lost and a new allocated floating IP will have a different address.

.. image:: /cloud/_img/op_fip_detach.jpg

.. tab-set::

    .. tab-item:: Ephemeral

        Ephemeral VMs have a fixed root volume size depending on the flavor available on the infrastructure. For this reason, the maximum size that can be reached by and ephemeral instance has an upper limit equal to the root volume size of the greatest flavor available. All the flavors available for each CINECA's HPC cloud infrastructures can be found in their dedicated pages grouped inside the :ref:`cloud_specifics_card` page.

        To increase such storage space, users need to create a new VM with a larger root volume using a snapshot of the original VM. The resulting virtual machine will be a bootable VM not an ephemeral. The resize operations can be performed both via the Horizon Dashboard and the OpenStack command line inteface.

        Create a snapshot of the VM instance following the instruction reported in the :ref:`compute_inst_snap_create_card` card.

        Once the snapshotting procedure is completed, create a new VM from the snapshot image. In the "Source" tab, select "Instance Snapshot" as boot source, use the option "Create New Volume" and choose the desired volume size.

        The complete list of instructions to instanciate a VM can be found in the :ref:`cloud/operative/compute_ops/instance_create:virtual machine creation` page.

        .. image:: /cloud/_img/op_inst_from_snap.jpg

    .. tab-item:: Bootable

        For all VMs created from a bootable volume, it is necessary to perform the resize operation of VM's Primary Volume to obtain a larger root disk size. The detailed procedure on how to perform such operation is illustrated in the :ref:`cloud/operative/storage_ops/volume_resize:resize a volume` page, "Primary Volume" tab.

        Once the primary volume resize procedure has been completed, create a new VM from the resized volume. In the "Source" tab, select "Volume" as boot source and choose the desired volume from the "Available" list.

        .. important::

          The added disk space will be automaticaly used for the extension of the exsiting disk.

        .. image:: /cloud/_img/op_inst_from_vol.jpg

.. important::

  Keep in mind that the SSH key used for accessing the snapshotted VM will be brought to the new one: adding a new SSH key is not mandatory if you still have access to the previous one.

  The flavor selected will affect the new VM only for what concerns vCPUs number and RAM amount.

  Be aware that the ``WARNING REMOTE HOST IDENTIFICATION HAS CHANGED`` message will arise when trying to ssh into the new instance if the floating IP assigned to the deleted VM will be assigned to the new one.

Finally, associate the old floating IP to the newly created VM

.. image:: /cloud/_img/op_fip_attach.jpg

Once the operation is completed, it is possible to remount any secondary volumes that were detatched at the start of this procedure.