nixpkgs/modules/services/torrent/transmission.nix

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# NixOS module for Transmission BitTorrent daemon
{ config, pkgs, ... }:
with pkgs.lib;
let
cfg = config.services.transmission;
homeDir = "/var/lib/transmission";
settingsDir = "${homeDir}/.config/transmission-daemon";
settingsFile = "${settingsDir}/settings.json";
# Strings must be quoted, ints and bools must not (for settings.json).
toOption = x:
if x == true then "true"
else if x == false then "false"
else if builtins.isInt x then toString x
else toString ''\"${x}\"'';
# All lines in settings.json end with a ',' (comma), except for the last
# line. This is standard JSON. But a comma can also appear *inside* some
# fields, notably the "rpc-whitelist" field. This is difficult to handle in
# sed so we simply ignore it and say that if you want to change the option at
# the last line of settings.json, you have to do it manually. At this time of
# writing, the last option is "utp-enable":true.
attrsToSedArgs = as:
concatStrings (concatLists (mapAttrsToList (name: value:
#map (x: '' -e 's=\(\"${name}\":\)[^,]*\(.*\)=\1 ${toOption x}\2=' '') # breaks if comma inside value field
map (x: '' -e 's=\(\"${name}\":\).*=\1 ${toOption x},=' '') # always append ',' (breaks last line in settings.json)
(if isList value then value else [value]))
as));
in
{
### configuration
options = {
services.transmission = {
enable = mkOption {
type = types.uniq types.bool;
default = false;
description = ''
Whether or not to enable the headless Transmission BitTorrent daemon.
Transmission daemon can be controlled via the RPC interface using
transmission-remote or the WebUI (http://localhost:9091/ by default).
Torrents are downloaded to ${homeDir}/Downloads/ by default and are
accessible to users in the "transmission" group.
'';
};
settings = mkOption {
type = types.attrs;
default =
{
# for users in group "transmission" to have access to torrents
umask = 2;
}
;
example =
{
download-dir = "/srv/torrents/";
incomplete-dir = "/srv/torrents/.incomplete/";
incomplete-dir-enabled = true;
rpc-whitelist = "127.0.0.1,192.168.*.*";
# for users in group "transmission" to have access to torrents
umask = 2;
}
;
description = ''
Attribute set whos fields overwrites fields in settings.json (each
time the service starts). String values must be quoted, integer and
boolean values must not.
See https://trac.transmissionbt.com/wiki/EditConfigFiles for documentation
and/or look at ${settingsFile}."
'';
};
rpc_port = mkOption {
type = types.uniq types.int;
default = 9091;
description = "TCP port number to run the RPC/web interface.";
};
};
};
### implementation
config = mkIf cfg.enable {
systemd.services.transmission = {
description = "Transmission BitTorrent Daemon";
after = [ "network.target" ];
wantedBy = [ "multi-user.target" ];
# 1) Only the "transmission" user and group have access to torrents.
# 2) Optionally update/force specific fields into the configuration file.
serviceConfig.ExecStartPre =
if config.services.transmission.settings != {} then ''
${pkgs.stdenv.shell} -c "chmod 770 ${homeDir} && mkdir -p ${settingsDir} && ${pkgs.transmission}/bin/transmission-daemon -d |& sed ${attrsToSedArgs config.services.transmission.settings} > ${settingsFile}.tmp && mv ${settingsFile}.tmp ${settingsFile}"
''
else ''
${pkgs.stdenv.shell} -c "chmod 770 ${homeDir}"
'';
serviceConfig.ExecStart = "${pkgs.transmission}/bin/transmission-daemon -f --port ${toString config.services.transmission.rpc_port}";
serviceConfig.ExecReload = "kill -HUP $MAINPID";
serviceConfig.User = "transmission";
# NOTE: transmission has an internal umask that also must be set (in settings.json)
serviceConfig.UMask = "0002";
};
# It's useful to have transmission in path, e.g. for remote control
environment.systemPackages = [ pkgs.transmission ];
users.extraUsers.transmission = {
group = "transmission";
description = "Transmission BitTorrent user";
home = homeDir;
createHome = true;
};
users.extraGroups.transmission = {};
};
}