Nested Groups & the children Keyword

Sometimes you want a group made of other groups. Ansible calls this a group of groups, built with the children keyword.

In INI, a header like [prod:children] declares a parent whose members are other group names, not hosts.

The child groups must exist with their own hosts. The parent then simply references them by name.

Target prod and Ansible reaches every host inside web and db. One name now covers a whole environment.

YAML nests naturally: a group lists more groups under its own children key, which can nest as deep as you like.

Combine layers like region and role: datacenter contains prod, which contains web and db. Inventory mirrors your org.

If web is a child of prod, a web host belongs to web and prod and all. Membership flows upward automatically.

Set a variable on the parent group and every child host inherits it, unless a more specific group overrides it.

A group cannot be a child of itself, directly or through a loop. Ansible rejects circular hierarchies when it parses.

Use the inventory graph to see your nesting clearly. The --graph flag draws parents and their children as a tree.

Nested groups let you say prod or web-prod precisely. As fleets grow, children keep targeting both broad and surgical.

You want a parent group whose members are the web and db groups. Which INI header do you use?

The children keyword nests groups into hierarchies. Hosts inherit every parent, and group variables flow down the tree. 🌳