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Tip of the Week 103 - Psick profiles. Part 5 - Managing /etc/hosts and DNS
Our tour of the ready to use profiles of the psick module continues this week with management of DNS entries for the resolver, and of the content of /etc/hosts file.
These are the previous posts of this series:
Part 1 - Overview of the psick module and its reusable profiles.
Part 2 - Proxy and Hostname settings with psick profiles.
Part 3 - OpenSSH settings, keys, configs management.
Part 4 - Users management.
Psick module provides 3 different classes to manage the contents of
psick::hosts::file: Manage /etc/hosts via a file resource
psick::hosts::dynamic: Manage /etc/hosts dynamically using exported resources
psick::hosts::resource: Manage /etc/hosts content via Puppet native
This class just manages /etc/hosts as a file, you can customise the template to use for the content of this file and an array of entries to add to it.
To use this approach, just classify your nodes with with profile:
Then it can be configured via Hiera with the following settings:
The erb template to use to manage the content of /etc/hosts (default value is
The ip address (default is the value of
$::psick::primary_ip which defaults to the fact
$::networking['ip']), the short hostname (defaults to fact
$::hostname) and the domain (defaults to fact
$::domain) to use to identify the local node in /etc/hosts:
psick::hosts::file::ipaddress: 10.12.13.14 psick::hosts::file::domain: example42.com psick::hosts::file::hostname: my_server
An array of custom extra lines to add to
/etc/hosts (default: ), each element of the array should contain the expected text in each extra line:
psick::hosts::file::extra_hosts: - 10.12.13.15 puppet puppet.example42.com - 10.12.13.20 other_server other_server.example42.com
This class manages /etc/hosts automatically and dynamically: each server managed by Puppet exports its own host entry (via Puppet
host resource) and collects the ones of all the other nodes.
The class provides options to customise IP and alias to export for a node, if to actually export the host entry and a special “magic var” which can be used to divide nodes in different groups (within each group hosts’ entries are exported and collected).
This class is alternative to the others, it requires Store configs enabled on the Puppet Server (so, consequently, the usage of PuppetDB in not too ancient setups) and can be used with a simple:
In small setups this could be enough to have /etc/hosts automatically managed with all the entries of all the nodes.
It’s possible anyway to customise some entries. For example the ip address (default
$::ipaddress) and the array of aliases (default
[ $::hostname ] to use when exporting the local host’s info):
psick::hosts::dynamic::dynamic_ip: 10.12.13.14 psick::hosts::dynamic::dynamic_alias: - my_server - my_server.example42.com - my_server_other_alias
It’s also possible to control if and how to export and collect the node’s host entry.
It’s possible to set a string that allows to group together nodes: all nodes having this magic var set collect and export host resources only for nodes using the same magic var:
If we don’t want to collect in any place the host entry of a node we can set, for it (default value is false, so each node exports a valid and collectable host resource):
Since /etc/hosts entries are managed via exported
host Puppet resources, it’s also possible to specify an Hash of custom additional entries to add to the host file. This makes sense if we want to add references to hosts or devices not managed by Puppet. The syntax of the hash to use maps the available arguments of the host resource (
puppet describe host for a full list):
psick::hosts::dynamic::extra_hosts: firewall.example42.com: ip: 10.12.13.1 target: /etc/hosts # (Default) host_aliases: - firewall - fw.example42.com san.example42.com: ip: 10.12.13.250 host_aliases: - san
This is the third alternative to manage /etc/hosts. It’s just a wrapper that exposes an Hiera controllable entry point for Puppet
host resource. This is alternative to the previous profiles and has to be classified as the others:
Configuration the is done via an Hash of hosts resources similar to what we have seen for
psick::hosts::resource::hosts: firewall.example42.com: ip: 10.12.13.1 target: /etc/hosts # (Default) host_aliases: - firewall - fw.example42.com san.example42.com: ip: 10.12.13.250 host_aliases: - san
Managing DNS resolver.
To manage the contents of
/etc/resolver you can use the
psick::dns::resolver profile. Classify it with something equivalent to :
And then configure on Hiera both the template to use and its entries.
To manage the template to use (default is ‘psick/dns/resolver/resolv.conf.erb’) and the actual path of the resolver file (default is ‘/etc/resolv.conf’):
psick::dns::resolver::resolver_path: /etc/resolv.conf psick::dns::resolver::resolver_template: profile/resolver/resolv.conf.erb
To manage the actual typical configuration settings of resolv.conf:
psick::dns::resolver::nameservers: - 220.127.116.11 - 18.104.22.168 psick::dns::resolver::options: - attempts: 2 - timeout: 2 - rotate psick::dns::resolver::search: - example42.com - lab.example42.com psick::dns::resolver::domain: example42.com psick::dns::resolver::sortlist: - 22.214.171.124/255.255.240.0 - 126.96.36.199
That’s all for today. As we have seen, for the most common use cases, on Linux systems, Psick provides ready to use profiles to manage the content of /etc/hosts and /etc/resolv.conf without the need of fetching dedicated modules.
Have fun with Puppet, Life, Universe and Everything.