ansible-useful-commands.md

Ansible useful commands

Directory Structure:

To create a role using the ansible-galaxy command, we can simply use the below syntax in our terminal:

ansible-galaxy init <ROLE_NAME>
# for example
ansible-galaxy init nginx

Simple Modules

Ping hosts

ansible <HOST_GROUP> -m ping
# for example
ansible localhost -m ping

Display gathered facts

ansible <HOST_GROUP> -m setup | less
# for example
ansible localhost -m setup | less

Filter gathered facts

ansible <HOST_GROUP> -m setup -a "filter=ansible_distribution*"
# for example
ansible localhost -m setup -a "filter=ansible_distribution*"

Copy SSH key manually

ansible <HOST_GROUP> -m authorized_key -a "user=root key='ssh-rsa AAAA...XXX == root@hostname'"
# for example
ansible localhost -m authorized_key -a "user=root key='ssh-rsa AAAA...XXX == root@hostname'"

Limit to one or more hosts

This is required when one wants to run a playbook against a host group, but only against one or more members of that group.

Limit to one host

ansible-playbook playbooks/PLAYBOOK_NAME.yml --limit "host1"

Limit to multiple hosts

ansible-playbook playbooks/PLAYBOOK_NAME.yml --limit "host1,host2"

Negated limit. NOTE: Single quotes MUST be used to prevent bash interpolation.

ansible-playbook playbooks/PLAYBOOK_NAME.yml --limit 'all:!host1'

Limit to host group

ansible-playbook playbooks/PLAYBOOK_NAME.yml --limit 'group1'

Limiting Tasks with Tags

Limit to all tags matching install

ansible-playbook playbooks/PLAYBOOK_NAME.yml --tags 'install'

Skip any tag matching sudoers

ansible-playbook playbooks/PLAYBOOK_NAME.yml --skip-tags 'sudoers'

Check for bad syntax

One can check to see if code contains any syntax errors by running the playbook.

Check for bad syntax:

ansible-playbook playbooks/PLAYBOOK_NAME.yml --syntax-check

Running a playbook in dry-run mode

Sometimes it can be useful to see what Ansible might do, but without actually changing anything.

One can run in dry-run mode like this:

ansible-playbook playbooks/PLAYBOOK_NAME.yml --check

Managing files

An ad hoc task can harness the power of Ansible and SCP to transfer many files to multiple machines in parallel. To transfer a file directly to all servers in the [atlanta] group:

ansible atlanta -m copy -a "src=/etc/hosts dest=/tmp/hosts"

The ansible.builtin.file module allows changing ownership and permissions on files. These same options can be passed directly to the copy module as well:

ansible webservers -m file -a "dest=/srv/foo/a.txt mode=600"
ansible webservers -m file -a "dest=/srv/foo/b.txt mode=600 owner=mdehaan group=mdehaan"

Install packages

ansible ad hoc command to install packages:

ansible localhost -a "apt install vim" --become
ansible all -i hosts.yml -a "apt install vim" --become
ansible all -i hosts.yml -m shell -a "apt install vim" --become

ansible fact and filter data

Facts include a large amount of variable data, filter useful data from it.

ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_os_family"
ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_nodename"
ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_interfaces"
ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_lsb"
ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_memory_mb"
ansible all -i inventories/hosts.yml -m setup  -a "filter=ansible_processor_vcpus"

Managing services

Ensure a service is started on all webservers:

ansible webservers -m ansible.builtin.service -a "name=httpd state=started"

Alternatively, restart a service on all webservers:

ansible webservers -m ansible.builtin.service -a "name=httpd state=restarted"

Ensure a service is stopped:

ansible webservers -m ansible.builtin.service -a "name=httpd state=stopped"
ansible all -i inventories/hosts.yml -m service -a 'name=nginx state=started'
ansible all -i inventories/hosts.yml -a 'systemctl status nginx'

Let’s verify the inventory that we have created.

ansible-inventory --list -y