# possible stupid question: selection of host groups and use of variables? **URL:** \ **Category:** Ansible Project\ **Created:** [December 6, 2012, 6:44am UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122 "2012-12-06T06:44:20Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Jonathan1](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jonathan1](https://forum.ansible.com/u/Jonathan1)\ **Post date:** [December 6, 2012, 6:44am UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/1 "2012-12-06T06:44:20Z")
Apologies in advance - I feel like this has been solved before but I am not coming up with much after searching ansible.cc and the group records. I am trying to make a playbook that I can use between different environments. I have application X deployed in a set of environments, dev, load testing, deployment testing, production, etc… and I want to use the same playbook to do some work and select the environment based on a variable. The host groups in question are named in a pattern to make this possible app\_x\_load\_test app\_x\_deployment\_test app\_x\_production and I want to reference them with something like: - hosts: app\_x\_$env tasks: - name: do something incredibly awesome action: dd bs=1M if=/dev/zero of=/tmp/foo but that doesn’t work so well… PLAY [app\_x\_$env] \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* no hosts matched I have a sneaking suspicion I am doing something stupid or terribly obvious, but any advice would be most welcome. cheers, Jonathan ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [December 6, 2012, 7:16am UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/2 "2012-12-06T07:16:41Z")
We have in a similar way dev, test en production hosts. Those are grouped per application, e.g. [app\_x\_dev] app\_x\_dev\_node1 app\_x\_dev\_node2 [app\_x\_test] app\_x\_test\_node1 Then a super group per app: [app\_x:children] app\_x\_dev app\_x\_test And then we have some more global groups, regrouping all test machines, all dev machines and all production machines. [dev:children] app\_x\_dev app\_y\_dev At playbook level we define a generic play for a certain app, deploying it to the [app\_x] group. When ran, we limit (--limit option to ansible-playbook) playbook execution to e.g. [dev] group. This is handled by some wrapper scripts calling ansible-playbook. HTH Serge ---
**Author:** ![Andreas\_Davour](https://avatars.discourse-cdn.com/v4/letter/a/bcef8e/32.png) [@Andreas\_Davour](https://forum.ansible.com/u/Andreas_Davour)\ **Post date:** [December 6, 2012, 8:56am UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/3 "2012-12-06T08:56:55Z")
I'm not sure if I understand what you're doing, since it looks complicated. But, this is how I use the same playbook against different tagets. hosts: $hostlist and then invoke ansible-playbook with --extra-vars="hostlist=webservers\_dev". Maybe some variation thereof is what you're looking for? /andreas ---
**Author:** ![Jonathan1](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jonathan1](https://forum.ansible.com/u/Jonathan1)\ **Post date:** [December 6, 2012, 7:02pm UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/4 "2012-12-06T19:02:39Z")
Andreas, Many thanks for the pointer. I stand by my prior statement that I was doing something a bit silly. What I was trying to do is to use the variable to replace a substring in the hostname - the “app\_x\_” section of the hostname is fixed, where the “app\_x\_$env” is variable. Basically was trying to be too tricky and I can easily use the variable name vs trying to do the substring replacement. cheers Jonathan ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [December 7, 2012, 4:28pm UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/5 "2012-12-07T16:28:20Z")
The hosts line is templated, so doing things like hosts: foo\_$x actually works fine, provided the variable "x" comes from --extra-vars It won't work if coming from inventory/elsewhere for that particular field as that hasn't been loaded quite yet. ---
**Author:** ![Jonathan1](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@Jonathan1](https://forum.ansible.com/u/Jonathan1)\ **Post date:** [December 7, 2012, 8:10pm UTC](https://forum.ansible.com/t/possible-stupid-question-selection-of-host-groups-and-use-of-variables/12122/6 "2012-12-07T20:10:10Z")
hrrm, must be doing something funny here (w/ v0.9) _# ansible-playbook -vvv --extra-vars “container=tomcat app\_package\_name=test env=dev version=1.2”_ _PLAY [database\_$env\_master] \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*_ _no hosts matched_ playbook contents: _- hosts: database\_$env\_master_ _tasks:_ _- name: do something awesome_ _action: blah blah blah_ will dig into this further if its possible this is an actual issue (vs. me doing something stupid)