This is a fragment of a playbook that I'm using (server.yml):
- name: Determine Remote User
hosts: web
gather_facts: false
roles:
- { role: remote-user, tags: [remote-user, always] }
My hosts file has different groups of servers, e.g.
[web]
x.x.x.x
[droplets]
x.x.x.x
Now I want to execute ansible-playbook -i hosts/<env> server.yml and override hosts: web from server.yml to run this playbook for [droplets].
Can I just override as a one time off thing, without editing server.yml directly?
Thanks.
I don't think Ansible provides this feature, which it should. Here's something that you can do:
hosts: "{{ variable_host | default('web') }}"
and you can pass variable_host from either command-line or from a vars file, e.g.:
ansible-playbook server.yml --extra-vars "variable_host=newtarget(s)"
For anyone who might come looking for the solution.
Play Book
- hosts: '{{ host }}'
tasks:
- debug: msg="Host is {{ ansible_fqdn }}"
Inventory
[web]
x.x.x.x
[droplets]
x.x.x.x
Command: ansible-playbook deplyment.yml -i hosts --extra-vars "host=droplets"
So you can specify the group name in the extra-vars
We use a simple fail task to force the user to specify the Ansible limit option, so that we don't execute on all hosts by default/accident.
The easiest way I found is this:
---
- name: Force limit
# 'all' is okay here, because the fail task will force the user to specify a limit on the command line, using -l or --limit
hosts: 'all'
tasks:
- name: checking limit arg
fail:
msg: "you must use -l or --limit - when you really want to use all hosts, use -l 'all'"
when: ansible_limit is not defined
run_once: true
Now we must use the -l (= --limit option) when we run the playbook, e.g.
ansible-playbook playbook.yml -l www.example.com
Limit option docs:
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'
This is a bit late, but I think you could use the --limit or -l command to limit the pattern to more specific hosts. (version 2.3.2.0)
You could have
- hosts: all (or group)
tasks:
- some_task
and then ansible-playbook playbook.yml -l some_more_strict_host_or_pattern
and use the --list-hosts flag to see on which hosts this configuration would be applied.
An other solution is to use the special variable ansible_limit which is the contents of the --limit CLI option for the current execution of Ansible.
- hosts: "{{ ansible_limit | default(omit) }}"
If the --limit option is omitted, then Ansible issues a warning, but does nothing since no host matched.
[WARNING]: Could not match supplied host pattern, ignoring: None
PLAY ****************************************************************
skipping: no hosts matched
I'm using another approach that doesn't need any inventory and works with this simple command:
ansible-playbook site.yml -e working_host=myhost
To perform that, you need a playbook with two plays:
first play runs on localhost and add a host (from given variable) in a known group in inmemory inventory
second play runs on this known group
A working example (copy it and runs it with previous command):
- hosts: localhost
connection: local
tasks:
- add_host:
name: "{{ working_host }}"
groups: working_group
changed_when: false
- hosts: working_group
gather_facts: false
tasks:
- debug:
msg: "I'm on {{ ansible_host }}"
I'm using ansible 2.4.3 and 2.3.3
I changed mine to default to no host and have a check to catch it. That way the user or cron is forced to provide a single host or group etc. I like the logic from the comment from #wallydrag. The empty_group contains no hosts in the inventory.
- hosts: "{{ variable_host | default('empty_group') }}"
Then add the check in tasks:
tasks:
- name: Fail script if required variable_host parameter is missing
fail:
msg: "You have to add the --extra-vars='variable_host='"
when: (variable_host is not defined) or (variable_host == "")
Just came across this googling for a solution. Actually, there is one in Ansible 2.5. You can specify your inventory file with --inventory, like this: ansible --inventory configs/hosts --list-hosts all
If you want to run a task that's associated with a host, but on different host, you should try delegate_to.
In your case, you should delegate to your localhost (ansible master) and calling ansible-playbook command
I am using ansible 2.5 (2.5.3 exactly), and it seems that the vars file is loaded before the hosts param is executed. So you can set the host in a vars.yml file and just write hosts: {{ host_var }} in your playbook
For example, in my playbook.yml:
---
- hosts: "{{ host_name }}"
become: yes
vars_files:
- vars/project.yml
tasks:
...
And inside vars/project.yml:
---
# general
host_name: your-fancy-host-name
Here's a cool solution I came up to safely specify hosts via the --limit option. In this example, the play will end if the playbook was executed without any hosts specified via the --limit option.
This was tested on Ansible version 2.7.10
---
- name: Playbook will fail if hosts not specified via --limit option.
# Hosts must be set via limit.
hosts: "{{ play_hosts }}"
connection: local
gather_facts: false
tasks:
- set_fact:
inventory_hosts: []
- set_fact:
inventory_hosts: "{{inventory_hosts + [item]}}"
with_items: "{{hostvars.keys()|list}}"
- meta: end_play
when: "(play_hosts|length) == (inventory_hosts|length)"
- debug:
msg: "About to execute tasks/roles for {{inventory_hostname}}"
This worked for me as I am using Azure devops to deploy an application using CICD pipelines. I had to make this hosts (in yml file) more dynamic so in release pipeline I can add it's value, for example:
--extra-vars "host=$(target_host)"
pipeline_variable
My ansible playbook looks like this
- name: Apply configuration to test nodes
hosts: '{{ host }}'
Related
I have to pass the host on which the Ansible command will be executed through extra vars.
I don't know in advance to which hosts the tasks will be applied to, and, therefore, my inventory file is currently missing the hosts: variable.
If I understood from the article "How to pass extra variables to an Ansible playbook" correctly, overwriting hosts is only possible by having already composed groups of hosts.
From the post Ansible issuing warning about localhost I gathered that referencing hosts to be managed in an Ansible inventory is a must, however, I still have doubts about it since the usage of extra vars was not mentioned in the given question.
So my question is: What can i do in order to make this playbook work?
- hosts: "{{ host }}"
tasks:
- name: KLIST COMMAND
command: klist
register: klist_result
- name: TEST COMMAND
ansible.builtin.shell: echo hi > /tmp/test_result.txt
... referencing hosts to be managed in an Ansible inventory is a must
Yes, that's the case. Regarding your question
What can I do in order to make this playbook work? (annot. without a "valid" inventory file)
you could try with the following workaround.
---
- hosts: localhost
become: false
gather_facts: false
tasks:
- add_host:
hostname: "{{ target_hosts }}"
group: dynamic
- hosts: dynamic
become: true
gather_facts: true
tasks:
- name: Show hostname
shell:
cmd: "hostname && who am i"
register: result
- name: Show result
debug:
var: result
A call with
ansible-playbook hosts.yml --extra-vars="target_hosts=test.example.com"
resulting into execution on
TASK [add_host] ***********
changed: [localhost]
PLAY [dynamic] ************
TASK [Show hostname] ******
changed: [test.example.com]
In any case it is recommended to check how to build your inventory.
Further Documentation
add_host module – Add a host (and alternatively a group) to the ansible-playbook in-memory inventory
I have a task which has meaning only if it has been run with full list of hosts (creating a /etc/ssh/ssh_known_hosts file). I want to skip this task if '--limit' has been used.
Is any way in ansible to detect if --limit option was used?
After some struggles I found a way:
- hosts: all
gather_facts: no
tasks:
- set_fact:
full_run: '{{play_hosts == groups.all}}'
...
- hosts: other_group
tasks:
- template: ...
when: full_run
In ansible, is it possible to get the value of the argument to the "--limit" option within a playbook? I want to do is something like this:
---
- hosts: all
remote user: root
tasks:
- name: The value of the --limit argument
debug:
msg: "argument of --limit is {{ ansible-limit-arg }}"
Then when I run he command:
$ ansible-playbook getLimitArg.yaml --limit webhosts
I'll get this output:
argument of --limit is webhost
Of course, I made up the name of the variable "ansible-limit-arg", but is there a valid way of doing this? I could specify "webhosts" twice, the second time with --extra-args, but that seems a roundabout way of having to do this.
Since Ansible 2.5 you can access the value using a new magic variable ansible_limit, so:
- debug:
var: ansible_limit
Have you considered using the {{ ansible_play_batch }} built-in variable?
- hosts: all
become: "False"
gather_facts: "False"
tasks:
- name: The value of the --limit argument
debug:
msg: "argument of --limit is {{ ansible_play_batch }}"
delegate_to: localhost
It won't tell you exactly what was entered as the argument but it will tell you how Ansible interpreted the --limit arg.
You can't do this without additional plugin/module. If you utterly need this, write action plugin and access options via cli.options (see example).
P.S. If you try to use --limit to run playbooks agains different environments, don't do it, you can accidentally blow your whole infrastructure – use different inventories instead.
Here is the small code block to achieve the same
- block:
- shell: 'echo {{inventory_hostname}} >> /tmp/hosts'
- shell: cat /tmp/hosts
register: servers
- file:
path: /tmp/hosts
state: absent
delegate_to: 127.0.0.1
- debug: var=servers.stdout_lines
Then use stdout_lines output as u wish like mine
- add_host:
name: "{{ item }}"
groups: cluster
ansible_user: "ubuntu"
with_items:
- "{{ servers.stdout_lines }}"
I'd like to pass a variable to an included Ansible playbook as follows:
---
- hosts: localhost
connection: local
vars:
my_group: foo
- include: site.yml hosts={{ my_group }}
Then, in site.yml...
---
- hosts: "{{ hosts }}"
...
Unfortunately, I get an error saying that my_group is undefined in site.yml. Ansible docs do say that:
Note that you cannot do variable substitution when including one playbook inside another.
Is this my case? Is there a way around it?
You can use this syntax, but my_group has to be defined at the global level. Now it's local to the first play - it's even clear from the indentation.
You can confirm this by running your playbook with --extra-vars my_group=foo.
But generally what you seem to want to achieve is done using in-memory inventory files and add_host module. Take this as an example:
- hosts: localhost
gather_facts: no
vars:
target_host: foo
some_other_variable: bar
tasks:
- add_host:
name: "{{ target_host }}"
groups: dynamically_created_hosts
some_other_variable: "{{ some_other_variable }}"
- include: site.yml
with site.yml:
---
- hosts: dynamically_created_hosts
tasks:
- debug:
var: some_other_variable
I added some_other_variable to answer the question from your comment "how do I make a variable globally available from inside a play". It's not global, but it's passed to another play as a "hostvar".
From what I see (and I can't explain why) in Ansible >=2.1.1.0, there must be an inventory file specified for the dynamic in-memory inventory to work. In older versions it worked with Ansible executed ad hoc, without an inventory file, but now you must run ansible-playbook with -i inventory_file or have an inventory file defined through ansible.cfg.
Helllo, what is the best way to make an included playbook run on the same hosts as the playbook that called him?
I've tried declaring a variable in the parent playbook with the host name and then passing it to the included playbook, but I get an error telling me that the variable is undefined.
Below is my playbook:
---
# Main staging configuration playbook
- vars:
host_name: "stage_ansible"
hosts: "{{ host_name }}"
remote_user: ubuntu
tasks:
- name: test connection
ping:
remote_user: ubuntu
- include: NginxDefinitions.yml
vars:
service_name: "interaction.qmerce.com"
env_name: "stage4"
host_name_pass: "{{ host_name }}"
...
and the error I'm receiving:
`ERROR! 'host_name' is undefined
If you want to define the hosts runtime and avoid hard coding them on the playbook, you can pass the hosts as extra variables on the command line.
To do so, remove vars definition from your first play and add the following to the ansible-playbook command line:
--extra-vars host_name=localhost
or when you have multiple hosts:
--extra-vars '{"host_name":["host1","host2","host3"]}'