transmission2qbt

A tool which imports / migrates all your torrents from Transmission to qBittorrent, while trying to preserve as much metadata as possible.

Python is not my native language, so please bear with me.

Why?

Most of the tools I could find simply used qBt's Web API to import torrents. This is fine for most usages but I wanted to keep some of the metadata that's saved in resume files, notably the original "added date" as well as the amount of data transferred so far.

Tested combinations

Resume data is not required or even expected to be kept in the exact same format between releases. This script operates on resume data directly so it might/will not work for all possible combinations of Transmission/qBittorrent/libtorrent-rasterbar.

The table here represents all combinations which have been tested by the author or have been reported by others as working.

Transmission	qBittorrent	libtorrent	OS	Issue
4.0.6	4.6.2	2.0.9	Linux	N/A
4.0.6	4.6.5	1.2.19.0	Linux	N/A
4.0.5	4.6.5	1.2.19.0	Linux	N/A
4.0.6	5.0.1	1.2.19.0	Linux	#1
2.94	5.0.1	2.0.11	Linux	N/A

Running

Please shut down both Transmission and qBittorrent before running this.

./transmission2qbt.py ~/.config/transmission ~/.local/share/data/qBittorrent/BT_backup

Predicate

The --predicate argument accepts a Python expression that can be used for filtering torrents which are going to be imported to qBt. The parsed torrent file is named parsed_tor and its associated Transmission resume data is resume_data. If the expression returns anything other than True or throws an exception, the torrent is skipped.

For example, this will only cause torrents using Debian's tracker whose name includes amd64 to be imported :

parsed_tor[b'announce'] == b'http://bttracker.debian.org:6969/announce'
and b'amd64' in parsed_tor[b'info'][b'name']

Mappings

• Transmission's "labels" become qBittorrent's "tags".
• Transmission's "bandwidth group" becomes qBittorrent's "category".

Paused torrents in Transmission are added as paused and "forced" in qBittorrent, as otherwise they start at the first run.

Directories

Transmission

* If the `TRANSMISSION_HOME` environment variable is set, its value is used.
* On Darwin, `"${HOME}/Library/Application Support/${appname}"` is used.
* On Windows, `"${CSIDL_APPDATA}/${appname}"` is used.
* If `XDG_CONFIG_HOME` is set, `"${XDG_CONFIG_HOME}/${appname}"` is used.
* `"${HOME}/.config/${appname}"` is used as a last resort.

as documented in transmission.h at the time of writing.

qBittorrent

The location of the "data directory" is not documented anywhere, so it's best to look at the source. Generally, you should look for BT_backup in :

• $HOME/.local/share/data/${qbt_profile_name} (legacy) or $HOME/.local/share/${qbt_profile_name} (non-legacy) on Linux,
• C:/Users/$USER/AppData/Local/qBittorrent/${qbt_config_name} on Windows,
• $HOME/Library/Application Support/qBittorrent/${qbt_config_name} on macOS.

If you use a profile directory specified via the --profile commandline option, then the location you want is ${profile_dir}/qBittorrent/data/BT_backup.

Limitations

• I couldn't figure out how to import Transmission data about the already available pieces, which means that all torrents will automatically be re-checked when qBittorrent is first run after the migration.

• If your Transmission is set to append .part to incomplete files, make sure you remove that suffix before running the migration, otherwise qBittorrent won't detect those files at all. Once qBt detects that a file is incomplete, it will append .!qBt itself if that option is enabled. This command will remove the .part suffix from all files in the current directory recursively :

find . -name '*.part' -exec /bin/bash -c 'for i in "$@"; do mv "$i" "${i%.part}"; done;' -- '{}' +

• This tool assumes that you're not using the - currently experimental - DB storage for resume data in qBittorrent.

• Transmission saves the binary form of one of its internal data structures, whose layout is dependent on the CPU and compiler being used, straight to the resume file. The current implementation was based on a Transmission compiled with gcc 13.2 on a x86_64 CPU running Linux.