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Pullconf

Pullconf is a configuration management system focused on Debian GNU/Linux and other Debian-based Linux systems. For those familiar with other configuration management systems, Pullconf's approach bears a strong resemblance to Puppet. Most importantly it employs a pull-based approach to configuration management, meaning a client periodically fetches its configuration from a central server and applies it.

The configuration that a client applies to itself is just a collection of resources (such as "file", "directory", "user" or "host"). Pullconf infers dependencies between resources automatically to the extent it is able to.

Pullconf does not try to do anything revolutionary in the space of configuration management systems. In fact it tries to be as boring and straightforward as possible. It might fit your needs when:

  • you operate a fleet of homogeneous server systems and your needs for extensive customization are thus low.
  • you are just getting started with system configuration management and other, more powerful systems such as Ansible, Puppet or Chef may be overkill.
  • all the resource types that you require are covered by Pullconf.
  • you do not care so much about DRY ("don't repeat yourself") and value having your client configuration in a comparatively flat structure, instead of having a multi-layered hierarchy and complex rules of inheritance.
  • you can live without a DSL (domain-specific language) that would enable you to conditionally include or exclude resources or resource parameters.
  • you want to turn your pet systems to cattle (to some extent), because it just happens that this is what configuration management systems are for.

More detailed information, installation instructions and configuration examples can be found at pullconf.dev.

Architecture

This section could use a nice drawing, but the architecture can also be explained in a few sentences:

A fleet of clients (Debian-based Linux servers) connects regularly with a central server to fetch their respective configuration/resource catalog. The configuration is stored on the server in a flat directory structure containing TOML files. Clients use their fully-qualified domain name/hostname and an API key to authenticate to the server.

Features

As already mentioned the resource catalog of a client is compiled from TOML files that follow a certain syntax. There are some features that allow you to manage your configuration effectively:

  • Resources can be collected into groups. A client can be a member of any number of groups. Clients inherit the resources defined in groups in addition to their own set of resources. The server prevents you from submitting ambiguous or invalid configuration and provides detailed error messages for conflict resolution. Meanwhile clients continue to be served with the most recent, valid configuration.
  • Variables can be defined per client and used throughout configuration files to substitute resource parameters.
  • Dependencies between resources are infered to some extent and applied in logical order. In addition explicit dependencies can be defined using the requires meta-parameter.

Documentation

... can be found at pullconf.dev!

Example

This is a basic example for a client configuration file to get a sense of the way TOML is used to define resources:

# /etc/pullconfd/resources/clients/blechbuechse.local.toml

api-key = "<...>"
groups = [ "sshd", "postfix", "nginx", "hardening" ]

[variables]
ip-address = "172.16.5.6"
proxy-ip-address = "172.16.10.5"

[[resources]]
type = "host"
# "$pullconf::hostname" is a pre-defined variable that evaluates to "blechbuechse.local".
hostname = "$pullconf::hostname"
ip-address = "$pullconf::ip-address"

[[resources]]
type = "host"
hostname = "proxy"
ip-address = "$pullconf::proxy-ip-address"
aliases = [ "proxy.local" ]

[[resources]]
type = "file"
path = "/etc/logrotate.d/rsyslog"
owner = "root"
group = "root"
mode = "0644"
content = """
/var/log/syslog
/var/log/mail.info
/var/log/mail.warn
/var/log/mail.err
/var/log/mail.log
/var/log/daemon.log
/var/log/kern.log
/var/log/auth.log
/var/log/user.log
/var/log/lpr.log
/var/log/cron.log
/var/log/debug
/var/log/messages
{
	rotate 4
	weekly
	missingok
	notifempty
	compress
	delaycompress
	sharedscripts
	postrotate
		/usr/lib/rsyslog/rsyslog-rotate
	endscript
}
"""

Future development

The basic building blocks for Pullconf are complete. In the future development will focus on adding more and more resource types to complement the very limited set of resources available at this time.