Launching a virtual instance with OpenStack_Linux：Powerful Server Administration-QQ阅读男生历史网

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Launching a virtual instance with OpenStack

Now that we have OpenStack installed and have set our desired operating system image, we are ready to launch our first instance in a self-hosted cloud.

Getting ready

You will need credentials to access the OpenStack dashboard.

Uploading your own image is not necessary; you can use the default Cirros image to launch the test instance.

Log in to the OpenStack dashboard and set the SSH key pair in the Access & Security tab available under the Projects menu. Here, you can generate a new key pair or import your existing public key.

Note

If you generate a new key pair, a file with the .pem extension will be downloaded to your local system. To use this key with PuTTy, you need to use PuTTYgen and extract the public and private keys.

How to do it…

OpenStack instances are the same virtual machines that we launch from the command line or desktop tools. OpenStack give you a web interface to launch your virtual machines from. Follow these steps to create and start a new instance:

Select the Instance option under the Projects menu and then click on the Launch Instance button on the right-hand side. This should open a modal box with various options, which will look something like this:
Now, start filling in the necessary details. All fields that are marked with * are required fields. Let's start by naming our instance. Enter the name in the Instance Name field.
Set the value of Count to the number of instances you want to launch. We will leave it at the default value of 1.
Next, click on the Source tab. Here, we need to configure the source image for our instance. Set Select Boot Source to Image and select No for Create New Volume. Then, from the Available Images section, search the desired image and click on the button with the + sign to select the image. The list should contain our recently uploaded image. The final screen should look something like this:
Next, on the Flavor tab, we need to select the desired resources for our instance. Select the desired flavor by clicking on the + button. Make sure that the selected row does not contain any warning signs.
Now, from the Key Pair tab, select the SSH key pair that we just created. This is required to log in to your instance.
Finally, click on the Launch Instance button from the bottom of the modal box. A new instance should be created and listed under the instances list. It will take some time to start; wait for the Status column to show Active:
You are now ready to access your virtual instance. Log in to your host console and try to ping the IP address of your instance. Then, open an SSH session with the following command:
```
$ ssh -i your_key ubuntu@instance_ip
```
This should give you a shell inside your new cloud instance. Try to ping an external server, such as an OpenDNS server, from within an instance to ensure connectivity.
To make this instance available on your local network, you will need to assign a floating IP address to it. Click on the drop-down arrow from the Actions column and select Associate Floating IP. This should add one more IP address to your instance and make it available on your local network.

How it works…

OpenStack instances are the same as the virtual machines that we build and operate with common virtualization tools such as VirtualBox and Qemu. OpenStack provides a central console for deploying and managing thousands of such machines on multiple hosts. Under the hood, OpenStack uses the same virtualization tools as the others. The preferred hypervisor is KVM, and if hardware acceleration is not available, Qemu emulation is used. OpenStack supports various other hypervisors, including VMware, XEN, Hyper-V, and Docker. In addition, a lightervisor, LXD, is on its way to a stable release. Other than virtualization, OpenStack adds various other improvements, such as image management, block storage, object storage, and various network configurations.

In the previous example, we set various parameters before launching a new instance; these include the instance name, resource constraints, operating system image, and login credentials. All these parameters will be passed to the underlying hypervisor to create and start the new virtual machine. A few other options that we have not used are volumes and networks. As we have installed a very basic OpenStack instance, new developments in network configurations are not available for use. You can update your DevStack configuration and install the OpenStack networking component Neutron.

Volumes, on the other hand, are available and can be used to obtain disk images of the desired size and format. You can also attach multiple volumes to a single machine, providing extended storage capacity. Volumes can be created separately and do not depend on the instance. You can reuse an existing volume with a new instance, and all data stored on it will be available to the new instance.

Here, we have used a cloud image to start a new instance. You can also choose a previously stored instance snapshot, create a new volume, or use a volume snapshot. The volume can be a permanent volume, which has its life cycle separate from the instance, or an ephemeral volume, which gets deleted along with the instance. Volumes can also be attached at instance runtime or even removed from an instance, provided they are not a boot source.

Other options include configuration and metadata. The configuration tab provides an option to add initialization scripts that are executed at first boot. This is very similar to cloud-init data. The following is a short example of a cloud-init script:

#cloud-config
package_update: true
package_upgrade: true
password: password
chpasswd: { expire: False }
ssh_pwauth: True
ssh_authorized_keys:
 - your-ssh-public-key-contents

This script will set a password for the default user (ubuntu in the case of Ubuntu images), enable password logins, add an SSH key to authorize keys, and update and upgrade packages.

The metadata section adds arbitrary data to instances in the form of key-value pairs. This data can be used to identify an instance from a group and automate certain tasks.

Once an instance has been started, you have various management options from the Actions menu available on the instance list. From this menu, you can create instance snapshots; start, stop, or pause instances; edit security groups; get the VNC console; and so on.

There's more…

Similar to the glance command-line client, a compute client is available as well and is named after the compute component. The nova command can be used to create and manage cloud instances from the command line. You can get detailed parameters and options with the nova help command or, to get help with a specific subcommand, nova help <subcommand>.