This is a historic page, please remove the {{historic}} tag if you plan to revive it.
(Originally by David Pfitzner,, see also Editing rulesets.


Rulesets allow modifiable sets of data for units, advances, terrain, improvements, wonders, nations, cities, governments and miscellaneous game rules, without requiring recompilation, in a way which is consistent across a network and through savegames.

  • To play Freeciv normally: don't do anything special; the new features all have defaults which give the standard Freeciv behaviour.
  • To play a game with rules more like Civ1, start the server with:
    ./ser -r data/civ1.serv
  • (and any other command-line arguments you normally use; depending on how you have Freeciv installed you may have to give the installed data directory path instead of "data").
Start the client normally. The client must be network-compatible (usually meaning the same or similar version) but otherwise nothing special is needed. (However some third-party rulesets may potentially require special graphics to work properly, in which case the client should have those graphics available and be started with an appropriate '--tiles' argument.)
As well as a Civ1 style as above, Freeciv now has a Civ2 style similary, although currently it is almost identical to standard Freeciv rules.
Note that the Freeciv AI might not play as well with rules other than standard Freeciv. The AI is supposed to understand and utilize all sane rules variations, so please report any AI failures so that they can be fixed.

The rest of this file contains:

  • More detailed information on creating and using custom/mixed rulesets.
  • Information on implementation, and notes for further development.

Using and modifying rulesetsEdit

Rulesets are specified using the server command "rulesetdir". The command above of "./ser -r data/civ1.serv" just reads a file which uses this command (as well as a few of the standard server options). The server command specifies in which directory the ruleset files are to be found.

The ruleset files in the data directory are user-editable, so you can modify them to create modified or custom rulesets (without having to recompile Freeciv). It is suggested that you _don't_ edit the existing files in the "default", "civ1" and "civ2" directories, but rather copy them to another directory and edit the copies. This is so that its clear when you are using modified rules and not the standard ones.

The format used in the ruleset files should be fairly self-explanatory. A few points:

  • The files are not all independent, since eg, units depend on advances specified in the techs file.
  • Units have a field, "roles", which is like "flags", but determines which units are used in various circumstances of the game (rather than intrinsic properties of the unit). See comments in common/unit.h

Properties of units and advances are now fairly well generalised. Properties of buildings are still rather inflexible.

UTF-8 is used in all data files and network transactions. Currently, some rulesets are in latin1 (ISO-8859-1). [See utility/fciconv.[ch]]

Restrictions and LimitationsEdit


  • At least one unit with role "FirstBuild" must be available from the start (i.e., tech_req = "None").
  • There must be units for these roles:
  • "Explorer"
  • "FerryBoat"
  • "Hut"
  • "Barbarian"
  • "BarbarianLeader"
  • "BarbarianBuild"
  • "BarbarianBoat" (move_type must be "Sea")
  • "BarbarianSea"
  • There must be at least one unit with flag "Cities".
  • These unit flag combinations won't work:
  • "Diplomat" and "Caravan"
  • These flags and roles work only for move_type "Land" units:
  • "Partisan"
  • "Settler"
  • "IgTer"
  • "Marines"
  • "Airbase"
  • "Barbarian"
  • "BarbarianTech"
  • These flags and roles work only for move_type "Sea" units:
  • "No_Land_Attack"

Implementation detailsEdit

This section and following section will be mainly of interested to developers who are familiar with the Freeciv source code.

Rulesets are mainly implemented in the server. The server reads the files, and then sends information to the clients. Mostly rulesets are used to fill in the basic data tables on units etc, but in some cases some extra information is required.

For units and advances, all information regarding each unit or advance is now captured in the data tables, and these are now "fully customizable", with the old enumeration types completely removed.

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