File-Sharing Services (GNU Guix Reference Manual)

10.8.14 File-Sharing Services

The (gnu services file-sharing) module provides services that assist with transferring files over peer-to-peer file-sharing networks.

Transmission Daemon Service

Transmission is a flexible BitTorrent client that offers a variety of graphical and command-line interfaces. A transmission-daemon-service-type service provides Transmission’s headless variant, transmission-daemon, as a system service, allowing users to share files via BitTorrent even when they are not logged in.

Scheme Variable: transmission-daemon-service-type

The service type for the Transmission Daemon BitTorrent client. Its value must be a transmission-daemon-configuration object as in this example:

(service transmission-daemon-service-type
         (transmission-daemon-configuration
          ;; Restrict access to the RPC ("control") interface
          (rpc-authentication-required? #t)
          (rpc-username "transmission")
          (rpc-password
           (transmission-password-hash
            "transmission" ; desired password
            "uKd1uMs9"))   ; arbitrary salt value

          ;; Accept requests from this and other hosts on the
          ;; local network
          (rpc-whitelist-enabled? #t)
          (rpc-whitelist '("::1" "127.0.0.1" "192.168.0.*"))

          ;; Limit bandwidth use during work hours
          (alt-speed-down (* 1024 2)) ;   2 MB/s
          (alt-speed-up 512)          ; 512 kB/s

          (alt-speed-time-enabled? #t)
          (alt-speed-time-day 'weekdays)
          (alt-speed-time-begin
           (+ (* 60 8) 30))           ; 8:30 am
          (alt-speed-time-end
           (+ (* 60 (+ 12 5)) 30))))  ; 5:30 pm

Once the service is started, users can interact with the daemon through its Web interface (at http://localhost:9091/) or by using the transmission-remote command-line tool, available in the transmission package. (Emacs users may want to also consider the emacs-transmission package.) Both communicate with the daemon through its remote procedure call (RPC) interface, which by default is available to all users on the system; you may wish to change this by assigning values to the rpc-authentication-required?, rpc-username and rpc-password settings, as shown in the example above and documented further below.

The value for rpc-password must be a password hash of the type generated and used by Transmission clients. This can be copied verbatim from an existing settings.json file, if another Transmission client is already being used. Otherwise, the transmission-password-hash and transmission-random-salt procedures provided by this module can be used to obtain a suitable hash value.

Scheme Procedure: transmission-password-hash password salt

Returns a string containing the result of hashing password together with salt, in the format recognized by Transmission clients for their rpc-password configuration setting.

salt must be an eight-character string. The transmission-random-salt procedure can be used to generate a suitable salt value at random.

Scheme Procedure: transmission-random-salt: Returns a string containing a random, eight-character salt value of the type generated and used by Transmission clients, suitable for passing to the transmission-password-hash procedure.

These procedures are accessible from within a Guile REPL started with the guix repl command (see Invoking guix repl). This is useful for obtaining a random salt value to provide as the second parameter to ‘transmission-password-hash‘, as in this example session:

$ guix repl
scheme@(guix-user)> ,use (gnu services file-sharing)
scheme@(guix-user)> (transmission-random-salt)
$1 = "uKd1uMs9"

Alternatively, a complete password hash can generated in a single step:

scheme@(guix-user)> (transmission-password-hash "transmission"
(transmission-random-salt))
$2 = "{c8bbc6d1740cd8dc819a6e25563b67812c1c19c9VtFPfdsX"

The resulting string can be used as-is for the value of rpc-password, allowing the password to be kept hidden even in the operating-system configuration.

Torrent files downloaded by the daemon are directly accessible only to users in the “transmission” user group, who receive read-only access to the directory specified by the download-dir configuration setting (and also the directory specified by incomplete-dir, if incomplete-dir-enabled? is #t). Downloaded files can be moved to another directory or deleted altogether using transmission-remote with its --move and --remove-and-delete options.

If the watch-dir-enabled? setting is set to #t, users in the “transmission” group are able also to place .torrent files in the directory specified by watch-dir to have the corresponding torrents added by the daemon. (The trash-original-torrent-files? setting controls whether the daemon deletes these files after processing them.)

Some of the daemon’s configuration settings can be changed temporarily by transmission-remote and similar tools. To undo these changes, use the service’s reload action to have the daemon reload its settings from disk:

# herd reload transmission-daemon

The full set of available configuration settings is defined by the transmission-daemon-configuration data type.

Data Type: transmission-daemon-configuration: The data type representing configuration settings for Transmission Daemon. These correspond directly to the settings recognized by Transmission clients in their settings.json file.

Available transmission-daemon-configuration fields are:

transmission-daemon-configuration parameter: package transmission: The Transmission package to use.

transmission-daemon-configuration parameter: non-negative-integer stop-wait-period

The period, in seconds, to wait when stopping the service for transmission-daemon to exit before killing its process. This allows the daemon time to complete its housekeeping and send a final update to trackers as it shuts down. On slow hosts, or hosts with a slow network connection, this value may need to be increased.

Defaults to ‘10’.

transmission-daemon-configuration parameter: string download-dir

The directory to which torrent files are downloaded.

Defaults to ‘"/var/lib/transmission-daemon/downloads"’.

transmission-daemon-configuration parameter: boolean incomplete-dir-enabled?

If #t, files will be held in incomplete-dir while their torrent is being downloaded, then moved to download-dir once the torrent is complete. Otherwise, files for all torrents (including those still being downloaded) will be placed in download-dir.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: maybe-string incomplete-dir

The directory in which files from incompletely downloaded torrents will be held when incomplete-dir-enabled? is #t.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: umask umask

The file mode creation mask used for downloaded files. (See the umask man page for more information.)

Defaults to ‘18’.

transmission-daemon-configuration parameter: boolean rename-partial-files?

When #t, “.part” is appended to the name of partially downloaded files.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: preallocation-mode preallocation

The mode by which space should be preallocated for downloaded files, one of none, fast (or sparse) and full. Specifying full will minimize disk fragmentation at a cost to file-creation speed.

Defaults to ‘fast’.

transmission-daemon-configuration parameter: boolean watch-dir-enabled?

If #t, the directory specified by watch-dir will be watched for new .torrent files and the torrents they describe added automatically (and the original files removed, if trash-original-torrent-files? is #t).

Defaults to ‘#f’.

transmission-daemon-configuration parameter: maybe-string watch-dir

The directory to be watched for .torrent files indicating new torrents to be added, when watch-dir-enabled is #t.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: boolean trash-original-torrent-files?

When #t, .torrent files will be deleted from the watch directory once their torrent has been added (see watch-directory-enabled?).

Defaults to ‘#f’.

transmission-daemon-configuration parameter: boolean speed-limit-down-enabled?

When #t, the daemon’s download speed will be limited to the rate specified by speed-limit-down.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-integer speed-limit-down

The default global-maximum download speed, in kilobytes per second.

Defaults to ‘100’.

transmission-daemon-configuration parameter: boolean speed-limit-up-enabled?

When #t, the daemon’s upload speed will be limited to the rate specified by speed-limit-up.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-integer speed-limit-up

The default global-maximum upload speed, in kilobytes per second.

Defaults to ‘100’.

transmission-daemon-configuration parameter: boolean alt-speed-enabled?

When #t, the alternate speed limits alt-speed-down and alt-speed-up are used (in place of speed-limit-down and speed-limit-up, if they are enabled) to constrain the daemon’s bandwidth usage. This can be scheduled to occur automatically at certain times during the week; see alt-speed-time-enabled?.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-integer alt-speed-down

The alternate global-maximum download speed, in kilobytes per second.

Defaults to ‘50’.

transmission-daemon-configuration parameter: non-negative-integer alt-speed-up

The alternate global-maximum upload speed, in kilobytes per second.

Defaults to ‘50’.

transmission-daemon-configuration parameter: boolean alt-speed-time-enabled?

When #t, the alternate speed limits alt-speed-down and alt-speed-up will be enabled automatically during the periods specified by alt-speed-time-day, alt-speed-time-begin and alt-time-speed-end.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: day-list alt-speed-time-day

The days of the week on which the alternate-speed schedule should be used, specified either as a list of days (sunday, monday, and so on) or using one of the symbols weekdays, weekends or all.

Defaults to ‘all’.

transmission-daemon-configuration parameter: non-negative-integer alt-speed-time-begin

The time of day at which to enable the alternate speed limits, expressed as a number of minutes since midnight.

Defaults to ‘540’.

transmission-daemon-configuration parameter: non-negative-integer alt-speed-time-end

The time of day at which to disable the alternate speed limits, expressed as a number of minutes since midnight.

Defaults to ‘1020’.

transmission-daemon-configuration parameter: string bind-address-ipv4

The IP address at which to listen for peer connections, or “0.0.0.0” to listen at all available IP addresses.

Defaults to ‘"0.0.0.0"’.

transmission-daemon-configuration parameter: string bind-address-ipv6

The IPv6 address at which to listen for peer connections, or “::” to listen at all available IPv6 addresses.

Defaults to ‘"::"’.

transmission-daemon-configuration parameter: boolean peer-port-random-on-start?

If #t, when the daemon starts it will select a port at random on which to listen for peer connections, from the range specified (inclusively) by peer-port-random-low and peer-port-random-high. Otherwise, it listens on the port specified by peer-port.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: port-number peer-port-random-low

The lowest selectable port number when peer-port-random-on-start? is #t.

Defaults to ‘49152’.

transmission-daemon-configuration parameter: port-number peer-port-random-high

The highest selectable port number when peer-port-random-on-start is #t.

Defaults to ‘65535’.

transmission-daemon-configuration parameter: port-number peer-port

The port on which to listen for peer connections when peer-port-random-on-start? is #f.

Defaults to ‘51413’.

transmission-daemon-configuration parameter: boolean port-forwarding-enabled?

If #t, the daemon will attempt to configure port-forwarding on an upstream gateway automatically using UPnP and NAT-PMP.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: encryption-mode encryption

The encryption preference for peer connections, one of prefer-unencrypted-connections, prefer-encrypted-connections or require-encrypted-connections.

Defaults to ‘prefer-encrypted-connections’.

transmission-daemon-configuration parameter: maybe-string peer-congestion-algorithm

The TCP congestion-control algorithm to use for peer connections, specified using a string recognized by the operating system in calls to setsockopt (or set to disabled, in which case the operating-system default is used).

Note that on GNU/Linux systems, the kernel must be configured to allow processes to use a congestion-control algorithm not in the default set; otherwise, it will deny these requests with “Operation not permitted”. To see which algorithms are available on your system and which are currently permitted for use, look at the contents of the files tcp_available_congestion_control and tcp_allowed_congestion_control in the /proc/sys/net/ipv4 directory.

As an example, to have Transmission Daemon use the TCP Low Priority congestion-control algorithm, you’ll need to modify your kernel configuration to build in support for the algorithm, then update your operating-system configuration to allow its use by adding a sysctl-service-type service (or updating the existing one’s configuration) with lines like the following:

(service sysctl-service-type
         (sysctl-configuration
          (settings
           ("net.ipv4.tcp_allowed_congestion_control" .
            "reno cubic lp"))))

The Transmission Daemon configuration can then be updated with

(peer-congestion-algorithm "lp")

and the system reconfigured to have the changes take effect.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: tcp-type-of-service peer-socket-tos

The type of service to request in outgoing TCP packets, one of default, low-cost, throughput, low-delay and reliability.

Defaults to ‘default’.

transmission-daemon-configuration parameter: non-negative-integer peer-limit-global

The global limit on the number of connected peers.

Defaults to ‘200’.

transmission-daemon-configuration parameter: non-negative-integer peer-limit-per-torrent

The per-torrent limit on the number of connected peers.

Defaults to ‘50’.

transmission-daemon-configuration parameter: non-negative-integer upload-slots-per-torrent

The maximum number of peers to which the daemon will upload data simultaneously for each torrent.

Defaults to ‘14’.

transmission-daemon-configuration parameter: non-negative-integer peer-id-ttl-hours

The maximum lifespan, in hours, of the peer ID associated with each public torrent before it is regenerated.

Defaults to ‘6’.

transmission-daemon-configuration parameter: boolean blocklist-enabled?

When #t, the daemon will ignore peers mentioned in the blocklist it has most recently downloaded from blocklist-url.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: maybe-string blocklist-url

The URL of a peer blocklist (in P2P-plaintext or eMule .dat format) to be periodically downloaded and applied when blocklist-enabled? is #t.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: boolean download-queue-enabled?

If #t, the daemon will be limited to downloading at most download-queue-size non-stalled torrents simultaneously.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: non-negative-integer download-queue-size

The size of the daemon’s download queue, which limits the number of non-stalled torrents it will download at any one time when download-queue-enabled? is #t.

Defaults to ‘5’.

transmission-daemon-configuration parameter: boolean seed-queue-enabled?

If #t, the daemon will be limited to seeding at most seed-queue-size non-stalled torrents simultaneously.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-integer seed-queue-size

The size of the daemon’s seed queue, which limits the number of non-stalled torrents it will seed at any one time when seed-queue-enabled? is #t.

Defaults to ‘10’.

transmission-daemon-configuration parameter: boolean queue-stalled-enabled?

When #t, the daemon will consider torrents for which it has not shared data in the past queue-stalled-minutes minutes to be stalled and not count them against its download-queue-size and seed-queue-size limits.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: non-negative-integer queue-stalled-minutes

The maximum period, in minutes, a torrent may be idle before it is considered to be stalled, when queue-stalled-enabled? is #t.

Defaults to ‘30’.

transmission-daemon-configuration parameter: boolean ratio-limit-enabled?

When #t, a torrent being seeded will automatically be paused once it reaches the ratio specified by ratio-limit.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-rational ratio-limit

The ratio at which a torrent being seeded will be paused, when ratio-limit-enabled? is #t.

Defaults to ‘2.0’.

transmission-daemon-configuration parameter: boolean idle-seeding-limit-enabled?

When #t, a torrent being seeded will automatically be paused once it has been idle for idle-seeding-limit minutes.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: non-negative-integer idle-seeding-limit

The maximum period, in minutes, a torrent being seeded may be idle before it is paused, when idle-seeding-limit-enabled? is #t.

Defaults to ‘30’.

transmission-daemon-configuration parameter: boolean dht-enabled?

Enable the distributed hash table (DHT) protocol, which supports the use of trackerless torrents.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: boolean lpd-enabled?

Enable local peer discovery (LPD), which allows the discovery of peers on the local network and may reduce the amount of data sent over the public Internet.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: boolean pex-enabled?

Enable peer exchange (PEX), which reduces the daemon’s reliance on external trackers and may improve its performance.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: boolean utp-enabled?

Enable the micro transport protocol (uTP), which aims to reduce the impact of BitTorrent traffic on other users of the local network while maintaining full utilization of the available bandwidth.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: boolean rpc-enabled?

If #t, enable the remote procedure call (RPC) interface, which allows remote control of the daemon via its Web interface, the transmission-remote command-line client, and similar tools.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: string rpc-bind-address

The IP address at which to listen for RPC connections, or “0.0.0.0” to listen at all available IP addresses.

Defaults to ‘"0.0.0.0"’.

transmission-daemon-configuration parameter: port-number rpc-port

The port on which to listen for RPC connections.

Defaults to ‘9091’.

transmission-daemon-configuration parameter: string rpc-url

The path prefix to use in the RPC-endpoint URL.

Defaults to ‘"/transmission/"’.

transmission-daemon-configuration parameter: boolean rpc-authentication-required?

When #t, clients must authenticate (see rpc-username and rpc-password) when using the RPC interface. Note this has the side effect of disabling host-name whitelisting (see rpc-host-whitelist-enabled?.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: maybe-string rpc-username

The username required by clients to access the RPC interface when rpc-authentication-required? is #t.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: maybe-transmission-password-hash rpc-password

The password required by clients to access the RPC interface when rpc-authentication-required? is #t. This must be specified using a password hash in the format recognized by Transmission clients, either copied from an existing settings.json file or generated using the transmission-password-hash procedure.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: boolean rpc-whitelist-enabled?

When #t, RPC requests will be accepted only when they originate from an address specified in rpc-whitelist.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: string-list rpc-whitelist

The list of IP and IPv6 addresses from which RPC requests will be accepted when rpc-whitelist-enabled? is #t. Wildcards may be specified using ‘*’.

Defaults to ‘("127.0.0.1" "::1")’.

transmission-daemon-configuration parameter: boolean rpc-host-whitelist-enabled?

When #t, RPC requests will be accepted only when they are addressed to a host named in rpc-host-whitelist. Note that requests to “localhost” or “localhost.”, or to a numeric address, are always accepted regardless of these settings.

Note also this functionality is disabled when rpc-authentication-required? is #t.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: string-list rpc-host-whitelist

The list of host names recognized by the RPC server when rpc-host-whitelist-enabled? is #t.

Defaults to ‘()’.

transmission-daemon-configuration parameter: message-level message-level

The minimum severity level of messages to be logged (to /var/log/transmission.log) by the daemon, one of none (no logging), error, info and debug.

Defaults to ‘info’.

transmission-daemon-configuration parameter: boolean start-added-torrents?

When #t, torrents are started as soon as they are added; otherwise, they are added in “paused” state.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: boolean script-torrent-done-enabled?

When #t, the script specified by script-torrent-done-filename will be invoked each time a torrent completes.

Defaults to ‘#f’.

transmission-daemon-configuration parameter: maybe-file-object script-torrent-done-filename

A file name or file-like object specifying a script to run each time a torrent completes, when script-torrent-done-enabled? is #t.

Defaults to ‘disabled’.

transmission-daemon-configuration parameter: boolean scrape-paused-torrents-enabled?

When #t, the daemon will scrape trackers for a torrent even when the torrent is paused.

Defaults to ‘#t’.

transmission-daemon-configuration parameter: non-negative-integer cache-size-mb

The amount of memory, in megabytes, to allocate for the daemon’s in-memory cache. A larger value may increase performance by reducing the frequency of disk I/O.

Defaults to ‘4’.

transmission-daemon-configuration parameter: boolean prefetch-enabled?

When #t, the daemon will try to improve I/O performance by hinting to the operating system which data is likely to be read next from disk to satisfy requests from peers.

Defaults to ‘#t’.