sudo apt-get install gimp-plugin-registryIf you prefer GUI installer, open Synaptic, search for gimp batch and mark for installation
To use the plugin, open Gimp and go to Filters -> Batch -> Batch Process... menu
Add files to be process at Input tab
Set value to whichever tab processes that you need and set the image type at Output tab (default is .bmp).
Click Start button.
Tested with GIMP v 2.6.10 on Linux Mint 64-bit.