Debugging Ansible

Question 1

First line of debugging is reading logs. The default ansible log formats can be intimidating for humans. How can you do?

Answer 1

Change the output format using ansible output callback plugin. The configiguration can be done in ansible.cfg

[defaults]
stdout_callback=debug

Question 2

SSH connection to hosts sometimes fail. How do you troubleshoot them?

Answer 2

Run the playbook with increased verbose level.

> ansible-playbook -vvv

or

> ansible-playbook -vvvv

Question 3

You want to see the value of a variable when running the playbook. What do you do?

Answer 3

use the debug module

• debug: var=myvariable
• debug msg=”The value of my variable is {{ var }}”
• debug var=hostvars[inventory_hostname]

Question 4

What is the playbook debugger?

Answer 4

Playbook debugger is an interactive debugger for ansible. When a task fails, ansible drops into the debugger.

Question 5

How do I enable ansible debugger?

Answer 5

Add the clause “strategy: debug” to the playbook.

Question 6

How do I navigate the ansible debugger?

Answer 6

using ansinble deugger commands:

p var: print a variable
r: rerun the failed task
c: continue executing the play
q: abort the play
task.args[key]=value: modify an argument
vars[key]=value modify a variable value

Question 7

What are example of variables supported by the ansible debugger?

Answer 7

task, result, vars, vars[key], task.args

Question 8

What is the use of the assert module?

Answer 8

assert module will fail the playbook with an error if a condition is not met.

Question 9

Provide an example using the assert plugin

Answer 9

• name: assert that eth1 exists
  assert:
  that: ansible_eth1 is defined

Question 10

What is the language used in assert statement?

Answer 10

Jinja2

Question 11

I want to assert that /etc/nginx is a directory. What do I do? Write the task.

Answer 11

1) Call the stat module to get stats on the file system
2) Assert of the type of file property that included in the provided stats

• name: stat /etc/nginx
  stat: /etc/nginx
  register: st
• name: assert that /etc/nginx is a dir
  assert:
  that: st.stat.isdir

Question 12

Ansible-playbook provides many flags that allow you to inspect or sanitize your playbook before running it. what are these flags?

Answer 12

• -syntax-check
• -list-hosts
• -list-tasks
• -check (run ansible in check mode/ dry run)
• -diff (show files changed on the managed hosts as result of execution)

Question 13

What mechanisms allow me to restrict the way I can run a playbook?

Answer 13

1) step: ansible prompts me before executing each task
2) start-at-task: start running playbook at given tag
3) –tags: run only tasks with a given tag

Question 14

How do I tag a task?

Answer 14

• name: run a command
  command: /opt/myprog
  tags:
  - bar
  - quux

Question 15

Provide a command for running playbook.yml with tags foo and quux

Answer 15

> ansible-playbook –tags=foo,quux playbook.yml

Question 16

Provide a command for running playbook.yml while skipping tasks tagged with foo and quux

Answer 16

> ansible-playbook –skip-tags=foo,quux playbook.yml