What rebuilder does is take rom files from the source directory, sorts them out and save the new file into the destination directory. If you have a complete set of MAME roms and a new update comes out.
Once you've downloaded the new roms you can use the rebuilder to look in the folder where the new roms are and create / fix sets of roms in your MAME folder.
Also, using the 0.138 set and updating to 0.143 or 0.144, I have 100% but after that, the total existing rom count practically doubles (200k ) and I never have the full set. A dat file for Clr Mame Pro you can download the 0.149 dat if you don't have it listed under Mame Dats, P. that site also has some of the art work and snaps and other great resources for mame P. extracting the packs before rebuilding is going to be the quickest option but it still takes an age P. I actually downloaded the sets myself from here, done that yesterday and today, managed to get every single rom that way If you run through the process again try extracting each set and update to it's own folder, rebuild from each folder alone just in case something messed up via the other rebuild 7349 is a rather large amount of sets to be missing :/ Also when you scan make sure all the fix options are on, otherwise it will not fix and miss named sets or roms and any other fixes.
then inside there i have a "0.139 to 0.140" folder contains the update roms ... - After the previous step has finished, you can remove the 0.140 and 0.140u1 rom paths from the list and do a refresh in RC. i have the full set of 0.139 in mame roms folder ... With this step, you copy all games that are new in 0.140 and 0.140u1 (did not exist in 0.139) to your master folder. In this step, RC will search for rom files that are missing from the 0.139 set in the other two folders and copy them to the games in the 0.139 folder.To do this point your source folder to the new roms and the destination folder to your MAME roms folder and then press the rebuild button.It is worthwhile to run a full scan both before and after a rebuild.The conventional way to update Retro Pie and install new features is through the setup script.
The setup script can be accessed from the Retro Pie menu in emulationstation.It does it by using the CRC32 checksums which are unique to each rom rather than using the rom name which can be very different from file to file.From the main start window press the rebuilder button and you will see this screen...It can also be accessed from the terminal with Core Packages Each section of the manage packages portion of the setup script have the option to install/update all packages and remove all installed packages.You can also update/install and remove packages individually.Please note that MAME is a registered trademark of Gregory Ember, and permission is required to use the "MAME" name, logo or wordmark.