Volume
A volume is a detachable block storage device (as a usb hard drive). This allows for persistent storage.
How to manage a volume?
By using openstack volume list comand line, you can list existing volumes.
Create a volume
To create a volume, use the following command line
$ openstack volume create --size <size> <volume-name>
You can create a volume from different types of sources.
It depends on the option you choose when creating the volume :
- default (no option) : to create a non-bootable volume,
- from an image - [
--image <image>] : often used to create a boot volume for an instance, - from a snapshot - [
--snapshot <snapshot>] of an instance, - from another volume - [
--source <volume>] : to clone a volume, - from a replicated volume - [
--source-replicated <replicated-volume>] : to clone a replica.
If you build a volume from a specified source then you don’t need to specify the size.
Resize a volume
To resize a volume, specify the ID (or the name) of the volume and a size (--size) larger than the old one.
The volume must not be attached to an instance.
$ openstack volume set <volume> --size <new-size>
Note that this command does not return any output but you can check the new volume size by displaying its information.
Delete a volume
Specify the ID (or name) of the volume and delete it using
$ openstack volume delete <volume>
Before deleting, make sure that an instance is not attached to the volume.
To verify that the volume is deleted, list the volumes.
$ openstack volume list
The volume should have the following status: status = deleting.
When completely deleted, it disappears from the list.
Please note that if the volume was not significant size, you may not have had time to see it appear in a deleted state in the volume list.
Volume and instance
Volumes can be attached and detached to instances at any time.
A volume can be attached to only one instance.
Attach a volume to instance
To attach a volume to an instance, please use openstack server add volume.
Then specify the ID or name for instance and volume.
$ openstack server add volume <instance> <volume>
Note that this command produces no output.
But you can check if the volume is properly attached to an instance by displaying its information.
$ openstack volume show <volume>
Detach a volume from instance
To detach a volume from instance, specify ID or name for instance and volume.
$ openstack server remove volume <instance> <volume>
Then display its information to check if it is no longer attached.
$ openstack volume show <volume>
Attachments line must be empty (attachments = []).
