Dependencies

The dependencies below are likely out of date. If you're installing on Ubuntu 12.04 with the reddit PPA set up, the list of packages installed by the Ubuntu Install Script is the most up to date and canonical source of information.

Servers

Dependency	Version	Ubuntu Package(s)	Description
PostgreSQL	9.0+	postgresql	Robust RDBMS. Used as primary data store.
Cassandra	1.0+	cassandra in ppa:reddit	Distributed database. Slowly becoming primary data store.
memcached	1.4+	memcached	Fast in-memory caching server. Used throughout reddit.
RabbitMQ	2.0+	rabbitmq-server	AMQP server. Used for offline processing.
HAProxy		haproxy	Load balancer for distributing requests to app servers.

Libraries

Dependency	Version	Ubuntu Package(s)	Description
Python	2.7.x	python-dev	Headers for building python modules.
Setuptools		python-setuptools	Provides easy_install and support for setup.py.
Pylons		python-pylons	Python Web application framework
libmemcached	0.32+	libmemcached6 and libmemcached-dev	For communication with memcached.
libpqxx		libpqxx-dev	C++ library for PostgreSQL.
gettext		gettext	Used for i18n support.
PyCAPTCHA		http://pypi.python.org/pypi/PyCAPTCHA

Misc. Utilities

Dependency	Version	Ubuntu Package(s)	Description
Git		git-core	reddit code is stored in Git.
GCC / G++		g++	GNU C++ Compiler. Used for compiling python modules etc.
Cython	0.14+	cython	Performance-intensive code is in Cython for speed.
daemontools		daemontools and daemontools-run	Simple daemon management system.
optipng		optipng	Used to compress auto-generated CSS spritemap.
psql		postgresql-client	CLI client for managing PostgreSQL.