# Subversion {#module-services-subversion}

[Subversion](https://subversion.apache.org/) is a centralized
version-control system. It can use a [variety of
protocols](https://svnbook.red-bean.com/en/1.7/svn-book.html#svn.serverconfig.choosing)
for communication between client and server.

## Subversion inside Apache HTTP {#module-services-subversion-apache-httpd}

This section focuses on configuring a web-based server on top of the
Apache HTTP server, which uses
[WebDAV](http://www.webdav.org/)/[DeltaV](http://www.webdav.org/deltav/WWW10/deltav-intro.htm)
for communication.

For more information on the general setup, please refer to the [the
appropriate section of the Subversion
book](https://svnbook.red-bean.com/en/1.7/svn-book.html#svn.serverconfig.httpd).

To configure, include in `/etc/nixos/configuration.nix` code to activate
Apache HTTP, setting [](#opt-services.httpd.adminAddr)
appropriately:

```nix
services.httpd.enable = true;
services.httpd.adminAddr = ...;
networking.firewall.allowedTCPPorts = [ 80 443 ];
```

For a simple Subversion server with basic authentication, configure the
Subversion module for Apache as follows, setting `hostName` and
`documentRoot` appropriately, and `SVNParentPath` to the parent
directory of the repositories, `AuthzSVNAccessFile` to the location of
the `.authz` file describing access permission, and `AuthUserFile` to
the password file.

```nix
services.httpd.extraModules = [
    # note that order is *super* important here
    { name = "dav_svn"; path = "${pkgs.apacheHttpdPackages.subversion}/modules/mod_dav_svn.so"; }
    { name = "authz_svn"; path = "${pkgs.apacheHttpdPackages.subversion}/modules/mod_authz_svn.so"; }
  ];
  services.httpd.virtualHosts = {
    "svn" = {
       hostName = HOSTNAME;
       documentRoot = DOCUMENTROOT;
       locations."/svn".extraConfig = ''
           DAV svn
           SVNParentPath REPO_PARENT
           AuthzSVNAccessFile ACCESS_FILE
           AuthName "SVN Repositories"
           AuthType Basic
           AuthUserFile PASSWORD_FILE
           Require valid-user
      '';
    }
```

The key `"svn"` is just a symbolic name identifying the virtual host.
The `"/svn"` in `locations."/svn".extraConfig` is the path underneath
which the repositories will be served.

[This page](https://wiki.archlinux.org/index.php/Subversion) explains
how to set up the Subversion configuration itself. This boils down to
the following:

Underneath `REPO_PARENT` repositories can be set up as follows:

```ShellSession
$ svn create REPO_NAME
```

Repository files need to be accessible by `wwwrun`:

```ShellSession
$ chown -R wwwrun:wwwrun REPO_PARENT
```

The password file `PASSWORD_FILE` can be created as follows:

```ShellSession
$ htpasswd -cs PASSWORD_FILE USER_NAME
```

Additional users can be set up similarly, omitting the `c` flag:

```ShellSession
$ htpasswd -s PASSWORD_FILE USER_NAME
```

The file describing access permissions `ACCESS_FILE` will look something
like the following:

```nix
[/]
* = r

[REPO_NAME:/]
USER_NAME = rw
```

The Subversion repositories will be accessible as
`http://HOSTNAME/svn/REPO_NAME`.