Host Name Patterns

Working with host name patterns

Working with Host Name Patterns

• If you want to use an IP address in a playbook, the IP address must be specified as such in the inventory.

• You cannot use IP addresses that are based only on DNS name resolving.

• So specifying an IP address in the playbook but not in the inventory file—assuming DNS name resolution is going to take care of the IP address resolving—doesn’t work.

• apart from the specified groups, there are the implicit host groups all and ungrouped.

• host name wildcards may be used.

  • ansible -m ping 'ansible\*'
    • match all hosts that have a name starting with ansible.
    • Must put the pattern between single quotes or it will fail with a no matching hosts error.
  • Can be used at any place in the host name.
    • ansible -m ping '\*ble1'

• When you use wildcards to match host names, Ansible doesn’t distinguish between IP addresses, host names, or hosts; it just matches anything.

  • 'web\*'
    • Matches all servers that are members of the group ‘webservers’, but also hosts ‘web1’ and ‘web2’.

To address multiple hosts:

• You specify a comma-separated list of targets to address multiple hosts:
  • ansible -m ping ansible1,192.168.4.202
  • Can be a mix of host names, IP addresses, and host group names.

Operators:

• Can specify a logical AND condition by including an ampersand (&), and a logical NOT by using an exclamation point (!).
  • web,&file applies to hosts only if they are members of the web and file groups
  • web,!webserver1 applies to all hosts in the web group, except host webserver1.
  • When you use the logical AND operator, the position of the ampersand doesn’t matter.
    • web,&file as &web,file also.
  • You can use a colon (:) instead of a comma (,), but using a comma is better to avoid confusion when using IPv6 addresses.