gcmtool is the primary program in the gcmtools suite. It is the program that you use to work directly with GameCube DVD images (.gcm and .iso).
If you run gcmtool with a GCM as a commandline argument, it'll dump
information about your game:
Mookid:~ spike$ gcmtool naruto2_JAP.gcm
System ID: G (Gamecube)
Game ID: NU
Region: J (Japan/NTSC)
Maker Code: DA (Tomy)
Game Name: NARUTO2
DOL offset: 128768
File count: 348
To see all of the available commandline options and information about
them, run gcmtool with the -? (or --help) option:
gcmbnrtool is used for working with opening.bnr found in the root directory of all GCMs. It contains extra information about the developer and game including a brief description of the game and a bitmap icon. gcmbnrtool can modify any of that information (unfortunately only in ASCII. So if you wanna put information in japanese, you're SOL), as well as extract the icon to a .raw (for photoshop) or even a .ppm (portable-pixel-map) format and inject your own custom icon (currently only from a .raw).
By default, gcmbnrtool will print out information about the .bnr:
Mookid:~ spike$ gcmbnrtool prince_opening.bnr
Name: Prince of Persia
Developer: UBISOFT Entertainment
Full Developer: Prince of Persia: The Sands of Time
Description: ? 2003 UBISOFT Entertainment
To see usage, run gcmbnrtool with the -? commandline option.