Chapter 12. Creating a customized instance

Procedure

1. Create a file with instructions for cloud-init. For example, create a bash script that installs and enables a web server on the instance:

   $ vim /home/scripts/install_httpd
   #!/bin/bash
   
   yum -y install httpd python-psycopg2
   systemctl enable httpd --now

2. Launch an instance with the --user-data option to pass the bash script:

   $ openstack server create \
   --image rhel8 \
   --flavor default \
   --nic net-id=web-server-network \
   --security-group default \
   --key-name web-server-keypair \
   --user-data /home/scripts/install_httpd \
   --wait web-server-instance

3. When the instance state is active, attach a floating IP address:

   $ openstack floating ip create web-server-network
   $ openstack server add floating ip web-server-instance 172.25.250.123

4. Log in to the instance with SSH:

   $ ssh -i ~/.ssh/web-server-keypair cloud-user@172.25.250.123

5. Check that the customization was successfully performed. For example, to check that the web server has been installed and enabled, enter the following command:

   $ curl http://localhost | grep Test
   <title>Test Page for the Apache HTTP Server on Red Hat Enterprise Linux</title>
   <h1>Red Hat Enterprise Linux <strong>Test Page</strong></h1>

6. Review the /var/log/cloud-init.log file for relevant messages, such as whether or not the cloud-init executed:

   $ sudo less /var/log/cloud-init.log
   ...output omitted...
   ...util.py[DEBUG]: Cloud-init v. 0.7.9 finished at Sat, 23 Jun 2018 02:26:02 +0000. Datasource DataSourceOpenStack [net,ver=2].  Up 21.25 seconds

Procedure

1. Launch an instance with the --property <key=value> option. For example, to mark the instance as a webserver, set the following property:

   $ openstack server create \
   --image rhel8 \
   --flavor default \
   --property role=webservers \
   --wait web-server-instance

2. Optional: Add an additional property to the instance after it is created, for example:

   $ openstack server set \
   --property region=emea \
   --wait web-server-instance

Procedure

1. Enable the config drive, and specify a file that contains content that you want to make available in the config drive. For example, the following command creates a new instance named config-drive-instance and attaches a config drive that contains the contents of the file my-user-data.txt:

   (overcloud)$ openstack server create --flavor m1.tiny \
     --config-drive true \
     --user-data ./my-user-data.txt \
     --image cirros config-drive-instance

   This command creates the config drive with the volume label of config-2, which is attached to the instance when it boots, and adds the contents of my-user-data.txt to the user_data file in the openstack/{version}/ directory of the config drive.

2. Log in to the instance.

3. Mount the config drive:

   • If the instance OS uses udev:

     # mkdir -p /mnt/config
     # mount /dev/disk/by-label/config-2 /mnt/config

   • If the instance OS does not use udev, you need to first identify the block device that corresponds to the config drive:

     # blkid -t LABEL="config-2" -odevice
     /dev/vdb
     # mkdir -p /mnt/config
     # mount /dev/vdb /mnt/config