transmission/docs/Environment-Variables.md

Users can set environmental variables to override Transmission's default behavior and for debugging.

Transmission-Specific Variables

• If TRANSMISSION_HOME is set, Transmission will look there for its settings instead of in the default location.
• If TRANSMISSION_WEB_HOME is set, Transmission will look there for the Web Interface files, such as the JavaScript, HTML, and graphics files.
• If TR_CURL_SSL_NO_VERIFY is set, Transmission will not validate SSL certificate for HTTPS connections when talking to trackers. See CURL's documentation (CURLOPT_SSL_VERIFYHOST and CURLOPT_SSL_VERIFYPEER) for more details.
• If TR_CURL_VERBOSE is set, debugging information for libcurl will be enabled. More information about libcurl's debugging mode is available here.
• If TR_DEBUG_FD is set to an integer, that integer is treated as a file descriptor and very verbose debugging information is written to it. For example, here is how to turn on debugging and save it to a file named "runlog" when running Transmission from a bash shell:

  $ export TR_DEBUG_FD=2
  $ transmission 2>runlog
  

• If TR_DHT_VERBOSE is set, Transmission will log all of the DHT's activities in excruciating detail to standard error.

Standard Variables Used by Transmission

• If TRANSMISSION_WEB_HOME is not set, non-Mac platforms will look for the Web Interface files in XDG_DATA_HOME and in XDG_DATA_DIRS as described in the XDG Base Directory Specification. XDG_DATA_HOME has a default value of $HOME/.local/share/.
• If TRANSMISSION_HOME is not set, Unix-based versions of Transmission will look for their settings in $XDG_CONFIG_HOME/transmission/. XDG_CONFIG_HOME has a default value of $HOME/.config/.
• If HOME is set, it is used in three ways:
  1. By the XDG variables, as described above.
  2. If TRANSMISSION_HOME is not set, Mac-based versions of Transmission will look for their settings in $HOME/Library/Application Support/Transmission.
  3. $HOME/Downloads is the default download directory.

Standard Variables Used by Other Tools

• Transmission uses the libcurl library for HTTP- and HTTPS-based tracker announces and scrapes. Transmission does not support proxies, but libcurl itself honors a handful of environment variables to customize its proxy behavior.