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Title of the Experiment

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4. Configure and Initialize

omni comes with a script, readyToLogin which finds the login information for nodes in your slice. As of omni version 2.8, readyToLogin has an --ansible-inventory flag which generates the Ansible inventory, which is a flat file which tells Ansible the name and login information for your nodes.

  1. Create your Ansible inventory file:

    On your local machine:

    $ readyToLogin MYSLICE --useSliceAggregates --ansible-inventory -o
    $ cat inventory

    Here example output of running these commands:

    $ readyToLogin ansible --useSliceAggregates --ansible-inventory -o
    Host info saved in inventory file: /Users/jdoe/projects/GENI/hellogeni/inventory
    $ cat inventory
    client  ansible_ssh_port=33850
  2. Check to see if your nodes are up and ready.

    This command uses the ping module to ping the specified nodes (in this case all) listed in the inventory file:

    $ ansible all -m ping -i inventory

    Example output showing all of the nodes responding to ping:

    $ ansible all  -m ping -i inventory
    client | success >> {
        "changed": false,
        "ping": "pong"
    server | success >> {
        "changed": false,
        "ping": "pong"
  3. Try using the ping module in Ansible to only ping server or client by replacing all in the above with server or client.

5. Execute Experiment

Tip The following are some example Ansible Ad Hoc commands. You can run these commands one at a time from the machine where you have Ansible installed. `-s` tells Ansible to use `sudo` when executing the command.

apt module is used to installed packages:

ansible [-i inventory] [all/server/client] -s -m apt -a "name=apache2 update_cache=yes"

shell module is used to execute an arbitrary shell command:

ansible [-i inventory] [all/server/client]  -s -m shell -a "/usr/sbin/a2enmod status"

file module is used to manipulate files:

ansible [-i inventory] [all/server/client] -s -m file -a "path=/var/www/html state=absent"

synchronize module is an implementation of rsync and is used to efficiently synchronize files between your local machine and the node:

ansible [-i inventory] [all/server/client] -s  -m synchronize \
    -a "src=website/index.html dest=/var/www"

lineinfile module is used to see if an arbitrary line exists in a file:

ansible [-i inventory] [all/server/client] -s  -m lineinfile \
     -a "line='ExtendedStatus On' dest=/etc/apache2/conf.d/extendedstatus create=yes state=present"

service module is used to start/stop/restart/etc services:

ansible [-i inventory] [all/server/client] -s  -m service -a "name=apache2 state=restarted"
Tip Ansible Ad Hoc commands easy map to commands used in an Ansible Playbook.

On the local machine:

ansible-playbook hello-server.yml -i inventory
ansible-playbook hello-client.yml -i inventory
  1. Using the above Ansible modules:
    1. on both client and server, install apache2 and iperf
    2. on the server node, place the website/index.html file in /var/www; do the same with the website/graphics files.
  2. Using the above Ansible modules, reproduce the steps in the HelloGENI install script. As you find a command that works, carefully copy it into a text file and then into the Playbook.

6. Analyze Experiment

  1. You may have noticed that the server playbook and the client playbook contained duplicate text. This is because both nodes need to have apache installed so that they can act as webservers. As you might have guessed, there is a way to modularize this configuration. In Ansible this is done with "roles".


Next: Finish