New lenses and cameras arrive at Lensfun every week. So, it is desirable to update your copy of Lensfun's database to stay up-to-date. In particular, if you have sent calibration pictures to Torsten's calibration service, you must update your local Lensfun database after the calibration in order to be able to use the new calibrations.
For this purpose, there exists a simple command-line tool called “update‑lensfun‑data”. If you call it (it doesn't need parameters), just wait for a second and the database is updated. It will report whether an update was necessary.
If you want the updates to be installed system-wide, the program needs root privileges. So call the program with “sudo lensfun‑update‑data” and enter your root password. There exists a second version of the programm called “g‑lensfun‑update‑data”. It will let you enter the root password – if new data is available – in a neat window. This version is especially useful for GUI programs, which can call it in the background.
If it is sufficient that the updates are available to only your user account, call “lensfun‑update‑data” without root priviledges. The updates are then written to ~/.local/share/lensfun/updates”.
In case there is more than one version of Lensfun on your system (e.g. you installed a new version, but the original version of your Linux distribution is still there and used by some programs), “lensfun‑update‑data” tries to detect this and updates the other database versions, too.