Running Ad Hoc Commands

The basic syntax consists of ansible then the host group from hosts to run against, -m <MODULE_NAME>, and optionally providing arguments via -a "OPT_ARGS"

Simple Modules

Ping hosts

ansible <HOST_GROUP> -m ping

Display gathered facts

ansible <HOST_GROUP> -m setup | less

Filter gathered facts

ansible <HOST_GROUP> -m setup -a "filter=ansible_distribution*"

Advanced Modules

Copy SSH key manually

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

Modify file using lineinfile

ansible all -m lineinfile -a "dest=/etc/group regexp='^(users:x:100:)(.*)' line='\1ldapusername,\2' state=present backrefs=yes"

Running Ansible as a different user

There are multiple ways to control which user account is used when executing Ansible. It can be controlled via a user's ~/.ssh/config, via remote_user in Ansible or through the Ansible inventory.

This has changed drastically between Ansible versions pre-2.0 and post 2.0

Follow this link to see how this can be done.

When running from the command line, one can just specify which user account to run against directly. Please note that specifying a user can sometime conflict with a user defined in /etc/ansible/hosts

Specifying a user:

ansible-playbook playbooks/atmo_playbook.yml --user atmouser

Using a specific SSH private key:

ansible -m ping hosts --private-key=~/.ssh/keys/id_rsa -u centos

Passing Variables via CLI

Variables can be pesky, but sometimes are required to be passed in via the CLI. Any variable can be set via the command line. Often the command line is the be all, end all in variable overrides.

Passing arguments:

ansible-playbook playbooks/atmo_playbook.yml -e "ATMOUSERNAME=atmouser"

Limiting Playbook/Task Runs

When writing Ansible, sometimes it is tedious to make a change in a playbook or task, then run the playbook It can sometimes be very helpful to run a module directly as shown above, but only against a single development host.

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'

Troubleshooting Ansible

http://docs.ansible.com/ansible/playbooks_checkmode.html

Busted Cache

Sometimes Ansible has a tendency to hold on to variables too long, which causes Ansible to think that a task/operation had already been done or changed when in fact it didn't.

A simple fix is to flush the redis cache during a code execution.

This can be done like this:

ansible-playbook playbooks/PLAYBOOK_NAME.yml --flush-cache

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

When all else fails

Modules

Sometimes Ansible just can't cut performing a task using the built-in modules. Raw module to the rescue!

Using raw module to run command similar to running directly via SSH:

ansible -m raw -s -a "yum install libselinux-python -y" new-atmo-images

Other times, Ansible's modules either aren't well defined yet, or simply do not exist. This is a use case for using shell and command modules. More information for shell and command modules.

The main differences between the two comes down to what kind of command one wishes to run. If the command uses IO redirection of ANY sort, use shell. If the command only contains CLI flags, command module will suffice.

Checking Redis

Command reference: http://redis.io/commands

Sometimes it may be neccessary to manually check Redis for gathered facts from a remote host. Redis is the default back-end for Ansible and usually is running as a server under 127.0.0.1. One can check Redis by performing the following steps:

  1. Log in to Ansible controller, if Ansible is not running on your local machine

  2. Login to Redis

    redis-cli

  3. List all stored entries for Ansible

    KEYS ansible*

  4. Find the entry for the remote host and display the gathered facts for that host

    MGET "ansible_factsXXX.XXX.XXX.XXX"

  5. Exit Redis

    quit

Manually flushing controller's redis cache

ansible localhost -m redis -a "command=flush flush_mode=all" -c local

Running Redis on OS X as a daemon

http://naleid.com/blog/2011/03/05/running-redis-as-a-user-daemon-on-osx-with-launchd

Write your own module

There is a wealth of modules available, and writing your own should only be done as an absolute last resort.

If you still wish to write your own, take a look at the docs here: http://docs.ansible.com/ansible/developing_modules.html