How Virtual Machines Are Created in OpenStack:

Step-by-Step Guide to Creating a VM in OpenStack: 

1. Log in to OpenStack CLI:

The first step is to log into the OpenStack command-line interface (CLI) by sourcing your OpenStack RC file. This file contains the credentials and environment variables necessary to authenticate you with OpenStack services.

# source <your-openrc-file.sh>

2. Select or Upload an Image:

VMs in OpenStack are booted from pre-defined images. You can either use an available image or upload your own. 

List available images:

# openstack image list

Upload a new image:

# openstack image create --disk-format qcow2 --container-format bare --file <IMAGE_PATH> <IMAGE_NAME>

This ensures you have the correct image available for booting the VM.

3. Create or Choose a Network:

A VM needs to be attached to a network for connectivity. If you don't have one, you can create a new network. 

Create a network:

# openstack network create <NETWORK_NAME>

Create a subnet for the network:

# openstack subnet create --network <NETWORK_NAME> --subnet-range 192.168.0.0/24 <SUBNET_NAME>

4. Select or Create a Flavor:

Flavors in OpenStack determine the size of the VM, specifying the number of vCPUs, memory, and disk space.

List available flavors:

# openstack flavor list

Create a new flavor (if required):

# openstack flavor create --ram 2048 --vcpus 2 --disk 20 <FLAVOR_NAME>

5. Set Up Security Groups:

Security groups act as virtual firewalls, controlling incoming and outgoing traffic for your VM.

List existing security groups:

# openstack security group list

Create a new security group:

#openstack security group create <SECURITY_GROUP_NAME>

Add rules to allow traffic (e.g., SSH):

# openstack security group rule create --proto tcp --dst-port 22 <SECURITY_GROUP_ID>

6. Launch the VM:

Now that you have selected an image, network, flavor, and security group, it’s time to launch the VM.

Launch a VM:

# openstack server create --flavor <FLAVOR_ID> --image <IMAGE_ID> --network <NETWORK_ID> --security-group <SEC_GROUP_ID> --key-name <KEY_NAME> <VM_NAME>

Check the VM status:

# openstack server list

Once the status changes to ACTIVE, the VM is successfully running. 

7. Assign a Floating IP (Optional):

To access the VM externally, you can associate a floating IP with it.

Create a floating IP:

# openstack floating ip create <EXTERNAL_NETWORK>

Assign the floating IP:

# openstack server add floating ip <VM_ID> <FLOATING_IP>

8. Access the VM:

Once the VM is up and running with a floating IP, you can SSH into the instance:

# ssh -i <KEY_FILE> <USERNAME>@<FLOATING_IP>