Ansible: Execute task only when a tag is specified

Point to tarsnap with a fully-qualified path, or set your PATH explicitly so it can find tarsnap. You can find the missing path element by logging in as root and executing which tarsnap

You don't mention what flavour of Linux you are using, so bear in mind that /bin/sh may very well not be the same as /bin/bash (eg. ~/.bashrc and ~/.bash_profile may not be read).

sudo -i will give you an 'interactive' shell. You should see the manual page for bash (if indeed you are using bash) to find out what 'interactivemeans (ie. which files are consulted). I think you'll find thatsudo -iwill read in ~/.bashrc, while justsudo(without-i`) will not.

The "tag" directive is misplaced in your code.

Your code should look like so:

---
# main playbook for cluster deployment

  # initial configuration of OS same for all hosts
- name: Cluster Deployer playbook
  hosts: all
  roles:
    - common
  tags: 
    - initial_config

  # configuration specific for loadbalancers hosts group
- name: Cluster Deployer playbook - Load Balancer setup
  hosts: loadbalancers
  roles:
    - loadbalancers_setup
  tags: 
    - setup_loadbalancer

  # configuration specific for db-servers hosts group
- name: Cluster Deployer playbook - Database servers setup
  hosts: db-servers
  roles:
    - db_servers_setup
  tags: 
    - setup_db_server

  # configuration specific for web-servers hosts group
- name: Cluster Deployer playbook - Web Servers setup
  hosts: web-servers
  roles:
    - web_servers_setup
  tags:
    - setup_web_server

And your ansible command should look like so:

ansible-playbook main.yml --inventory hosts --tags "initial_config"

For more information, check Ansible's official documentation.