This is a collection of scripts which eases life of a system administrator. There is a single configuration file for all managed machines and a number of utilities which generate uniform settings for many services, including:

• Networking (DHCP, forward and reverse DNS, iptables port forwarding and access rules, Nginx reverse proxy etc);
• Monitoring (generate Nagios config based on all declared hosts and services);
• Computation services (SLURM configs and distcc machine hosts are dynamically generated with proper machine resources declaration, allowing to exploit all available computing power);
• SSH known hosts for secure access (all machines automatically and securely explore each other public keys without any administrator intervention and generate single shell script which manages keys for all hosts);
• Centralised configuration of managed hosts. Puppet is heavily used and manifests are derived from templates and main configuration file. This ensures consistent system configuration on a number of hosts;
• various useful utilities, e.g. quickly wake up a host with Wake-on-LAN by host name or alias, or build a network map using information from config file and ARP tables on network devices.

The structure of the project is as follows:

• cfg/: this is the directory with the main config file (conf.yaml) and various templates for other files. Templates are written using Jinja2 templating language. The main configuration file uses very convenient and concise YAML syntax;
• nagios/: this is where some files useful for [Nagios] (http://www.nagios.org/) reside;
• parse/: this directory contains Python code for parsing and validating the main config file and other auxiliary files;
• gen/: this directory contains Python code for generating a lot of things (config files, scripts etc.) using templates and the state parsed from the main config file;
• puppet/: this directory contains [Puppet] (http://puppetlabs.com/puppet/what-is-puppet) modules and other Puppet-specific stuff.
• util/: some useful stuff which does not belong to cathegories listed above resides here, mainly there are a bunch of Bash scripts.

There are two entry points. Main.py is a Python script for executing a generation process which only operates with templates and other text stuff and does not touch the system in any way. On the other hand there is do.sh Bash script which is a wrapper for main.py and does actual work generating configuration of various services and takes care of reload/restart signaling when it is necessary. It contains a number of shell functions which may be used separately or in batch mode. Every function in this file does some piece of configuration in such a way that a service is touched only if it is necessary. This enables the following scenario for the administrator: edit conf.yaml, check, commit, then simply execute do.sh and it will automatically apply all relevant changes.

The main configuration file (conf.yaml) consists of a number of sections, each of which represents a list of entities of some kind:

• People. This is a list of nicknames along with their associated contact information, useful for e-mail notifications from monitoring, automatic updates and other services.
• Defaults. This section contanins a bunch of default values for other sections, such as default monitoring host IP address or default network prefix in host descriptions (which may be omitted to avoid duplication).
• Networks. This is a list of IPv4 (and, in future, maybe IPv6) networks known to the system. Each network may have some attributes, e.g. rdns means that we should build reverse DNS zone for this network, while dhcp defines a range of IP addresses that should be used by DHCP server for dynamic IP address pool and so on.
• Groups. Groups define properties common for a number of hosts to avoid duplication and provide more structure. Their second purpose is to add some grouping for hosts to services that support grouping functionality natively (for example, Nagios or SLURM). Every group has unique name, may contain a list of hosts (which are defined using Python regular expression syntax) or other groups, and may define a list of properties which should apply to all contained entities.
• Hosts. The rest of main config file is a long list of hosts known to the system. Each host has a host name as the only required attribute, which goes first in it's description. It may have some shorter names called aliases, which help to identify it with one or two letters in many places. Host may have an IP address, a number of MAC addresses associated with it, and a dictionary of properties. Host properties define some host-specific data, for example who admins that host (see People above), which services this host has, what UDP ports sholud be forwarded to that host or what UPS powers it. Propertes may have arbitrary structure convenient for specific purpose (for example, running services are most naturally expressed as a list). The names and semantics of properties are defined by templates and generation code which uses them. Unsupported properties are quietly skipped.

As the main config file is read and written entirely by humans, there are two main thoughts which constitute it's philosophy:

• All terms should be self-descripting. If someone sees something which looks like MAC address, that should be so. And if there is https in some place, you should't have to look through the documentation to find out what it is.
• Duplication should be avoided as much as possible. Less duplication means less code to read and, consequently, less errors. Group functionality, although somewhat odd and complicated, was specifically developed for this purpose. Also there are host aliases, default network prefixes, regular expressions and generally beautiful and clean YAML markup which all serve this purpose.