Thank you rbino for the ems-qart program, it works really well. At the moment I was using the Android app which is cool too (and can backup individual lsdj songs), but I appreciate to be able to handle the sav and roms from my linux computer too!
The ems-flasher with multi-rom is great too even if I'd prefer to use ems-qart, except for multi roms.
You can grab the menu.gb or menu.gbc rom from here, concatenate the roms you want onto it
is there a way to concatenate roms from a command line (without flashing to cart)? I've tried with "cat menu.gb rom1.gb rom2.gb > myrom.gb" and I've transfered myrom.gb. I've got the list of the roms / games on it, but whenever I try to launch on of them, the screen remains blank. Otherwise ems-flasher works fine if you send the roms directly on the cart, from the command line (some doesn't work though, but might work if you transfer them with a new set of roms).