instance

Adventures in OpenStack – On-Disk Anatomy of an Instance

vancluevertech, ,

When an instance is set up and started on OpenStack, the base image will be copied over and stored the local compute node from Glance. Here is what it looks like on disk, from a test instance of mine:

/var/lib/nova/instances/646d10cb-a5f5-4669-a155-cc78b5d59406
# ls -al 
total 65628
drwxr-xr-x. 2 nova nova       69 Feb 12 23:30 .
drwxr-xr-x. 5 nova nova       93 Feb 12 23:30 ..
-rw-rw----. 1 root root    14796 Feb 13 00:17 console.log
-rw-r--r--. 1 root root 67174400 Feb 13 00:17 disk
-rw-r--r--. 1 nova nova       79 Feb 12 23:29 disk.info
-rw-r--r--. 1 nova nova     2629 Feb 12 23:43 libvirt.xml

And checking the disk file, we see the following:

# qemu-img info disk
image: disk
file format: qcow2
virtual size: 5.0G (5368709120 bytes)
disk size: 64M
cluster_size: 65536
backing file: /var/lib/nova/instances/_base/acc45e1bf0ad2336505dcad48418ce2564b701c4
Format specific information:
    compat: 1.1
    lazy refcounts: false

Also, while the user instance disk is qcow2, the backing file is *not*:

image: /var/lib/nova/instances/_base/acc45e1bf0ad2336505dcad48418ce2564b701c4
file format: raw
virtual size: 2.0G (2147483648 bytes)
disk size: 1.1G

Remember that instance storage for Nova needs to be engineered properly: /var/lib/nova/instances could be local, but should be shared or replicated storage to ensure proper availability levels.

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Adventures in OpenStack – Launching an Instance, and Attaching a Floating IP

vancluevertech, , , ,

Now that I have all the basic building blocks set up, I can proceed to setting up an instance.

Incidentally, packstack set most of this up already, but I actually ripped out most of the networking stuff created by packstack, and also removed the demo tenant and set all that stuff up from scratch. I’m glad I did, as I have a lot better understanding as to what is going on with that part now. Understanding of Cinder and Swift is not necessarily nearly as important on a single server cloud as far as I’m concerned, and can be looked into later.

In any case, time to get started.

Make sure that the correct tenant is selected before doing any of this – admin is not the correct one! I may address this in a later article, but you either want to make sure that admin has correct permission for the project, or log in as the project’s admin user.

Adding a Key Pair

Instances cannot be logged into over SSH if there is no key pair.

Go to Projects -> Compute -> Access and Security. Under Key Pairs, a key pair can either be created, or imported. Importing brings up this window which you can put in your own OpenSSH public key:

OpenStack - Import Key Pair

Creating a key pair will create a key pair, and then automatically download it.

Adding SSH Access Rules

Under Projects -> Compute -> Access and Security -> Security Groups, a firewall rule needs to be added for SSH. Click Add Rule after selecting the default security group and enter the following:

OpenStack - Security Group Rule

This allows SSH globally. Rules can also be made to link security groups, allowing you to create more sophisticated access schemes across different networks.

Instance Creation

Time to create the instance.

Head to Project -> Compute -> Instances and click Launch Instance:

OpenStack - Create Instance 1

OpenStack - Create Instance 2

OpenStack - Create Instance 3

Note the options. I am using preconfigured flavours with the Debian Jessie image I uploaded. I am also using a test key pair, and the network I created.

Post-Creation gives you a place to add any post-installation scripts and what not, and Advanced Options allows you to set up custom partitioning if you want. I don’t need either of those, so I did not include them or modify them.

After clicking Launch, and waiting a bit of time, the instance should be visible:

OpenStack - Running Instance

I can now proceed to attaching a floating IP, so that the instance is publicly accessible.

Adding a Floating IP Address

Click the drop down box at the far right of the instance listing and select Associate Floating IP:

OpenStack - Floating IP 1

Since I do not have any IPs allocated, I have to request one, by clicking the + (plus) button:

OpenStack - Floating IP 2

I can then use the allocation given to me:

OpenStack - Floating IP 3

And now the IP address will be visible in the instance, after clicking Associate of course:

OpenStack - Floating IP 4This instance is now ready to log into! By connecting using the SSH key I was given, I can connect to 172.16.0.13 over SSH and start working on the instance.

The Debian image’s default login at this time is debian. Most instances will NOT let you log in as root, so consult the image documentation for any specific default user that is created. Sometimes, logging in as root will give you the correct user to log in as and then disconnect you (such is the case with the Debian image).

Adventures in OpenStack – Uploading an Image

vancluevertech, ,

Images are, of course, the base data that you launch an instance off of. The concept is obviously not new to OpenStack and has been a key feature since the birth of cloud computing. It serves to optimize the virtualization process by de-duplicating the storage and I/O necessary to run an instance.

You can add an image into OpenStack directly via supplying its URL, or uploading directly from your machine. There are also other options, referenced in the manuals below.

The following screenshot below is the screen you see when you upload an images thru Project -> Compute -> Images:

(A note about the above: I wanted initially to upload this to Admin -> System -> Images, but there I did not seem to have permission, even though I was following the procedure as followed in the first URL at the end of this article. Looking at the logs, I saw some error messages saying that glance-api had a bad request for the “x-image-meta-protected” header. I think this is a bug – uploading however thru the admin project works.)

OpenStack - New Image

Here, we are uploading a Jessie image directly from the hard drive.

Some more info can be found here: