Instance building blocks
In OpenStack, the base operating system is usually copied from an
image stored in the OpenStack Image Service. This results in an
ephemeral instance that starts from a known template state and loses all
accumulated states on shutdown.
You can also put an operating system on a persistent volume in
Compute or the Block Storage volume system. This gives a more traditional,
persistent system that accumulates states that are preserved across
restarts. To get a list of available images on your system, run:
$ nova image-list
+--------------------------------------+-------------------------------+--------+--------------------------------------+
| ID | Name | Status | Server |
+--------------------------------------+-------------------------------+--------+--------------------------------------+
| aee1d242-730f-431f-88c1-87630c0f07ba | Ubuntu 14.04 cloudimg amd64 | ACTIVE | |
| 0b27baa1-0ca6-49a7-b3f4-48388e440245 | Ubuntu 14.10 cloudimg amd64 | ACTIVE | |
| df8d56fc-9cea-4dfd-a8d3-28764de3cb08 | jenkins | ACTIVE | |
+--------------------------------------+-------------------------------+--------+--------------------------------------+
The displayed image attributes are:
ID
Automatically generated UUID of the image.
Name
Free form, human-readable name for the image.
Status
The status of the image. Images marked
ACTIVE are available
for use.
Server
For images that are created as snapshots of
running instances, this is the UUID of the
instance the snapshot derives from. For
uploaded images, this field is blank.
Virtual hardware templates are called flavors.
The default installation provides five predefined flavors.
For a list of flavors that are available on your system, run:
$ nova flavor-list
+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| ID | Name | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public |
+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
| 1 | m1.tiny | 512 | 1 | 0 | | 1 | 1.0 | True |
| 2 | m1.small | 2048 | 20 | 0 | | 1 | 1.0 | True |
| 3 | m1.medium | 4096 | 40 | 0 | | 2 | 1.0 | True |
| 4 | m1.large | 8192 | 80 | 0 | | 4 | 1.0 | True |
| 5 | m1.xlarge | 16384 | 160 | 0 | | 8 | 1.0 | True |
+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
By default, administrative users can configure the flavors. You
can change this behavior by redefining the access controls for
compute_extension:flavormanage in
/etc/nova/policy.json on the
compute-api server.