Instance building blocks
In OpenStack, the base operating system is usually copied from an image stored in the
OpenStack Image Service. This is the most common case and 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, which 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 12.04 cloudimg amd64 | ACTIVE | |
| 0b27baa1-0ca6-49a7-b3f4-48388e440245 | Ubuntu 12.10 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 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 flavors. By default, these are configurable by administrative
users. However, you can change this behavior by redefining the access controls for
compute_extension:flavormanage in
/etc/nova/policy.json on the compute-api
server.
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 |
+----+-----------+-----------+------+-----------+------+-------+-------------+
| 1 | m1.tiny | 512 | 1 | N/A | 0 | 1 | |
| 2 | m1.small | 2048 | 20 | N/A | 0 | 1 | |
| 3 | m1.medium | 4096 | 40 | N/A | 0 | 2 | |
| 4 | m1.large | 8192 | 80 | N/A | 0 | 4 | |
| 5 | m1.xlarge | 16384 | 160 | N/A | 0 | 8 | |
+----+-----------+-----------+------+-----------+------+-------+-------------+