[Solved] How to fix "format of this zipfile is not supported"

[Lolonois]

FWIW, I ran into the same issue as here, but it is somewhat buried in a long thread and AFAIK has never got a concise answer.

Synopsis: For some ROMs (esp. MAME based) you can get an error message like below and the game won't start.

$ cat /dev/shm/runcommand.log
Parameters:
Executing: /opt/retropie/emulators/retroarch/bin/retroarch -L /opt/retropie/libretrocores/lr-mame2003/mame2003_libretro.so --config /opt/retropie/configs/mame-libretro/retroarch.cfg "/home/pi/RetroPie/roms/mame-libretro/pacman.zip" --appendconfig /dev/shm/retroarch.cfg
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
Error in zipfile pacman.zip
The format of this zipfile is not supported, please recompress it
pacman.5e    NOT FOUND
pacman.5f    NOT FOUND
82s123.7f    NOT FOUND
82s126.4a    NOT FOUND
82s126.1m    NOT FOUND
82s126.3m    NOT FOUND
ERROR: required files are missing, the game cannot be run.

Then check the rom in question with zipinfo:

$ zipinfo pacman.zip
Archive:  pacman.zip
Zip file size: 25671 bytes, number of entries: 15
-rw-r--r--  6.3 unx       32 bx defN 96-Dec-24 23:32 82s123.7f
-rw-r--r--  6.3 unx      256 bx defN 96-Dec-24 23:32 82s126.1m
-rw-r--r--  6.3 unx      256 bx defN 96-Dec-24 23:32 82s126.3m
-rw-r--r--  6.3 unx      256 bx defN 96-Dec-24 23:32 82s126.4a
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 namcopac.6e
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 namcopac.6f
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 namcopac.6h
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 namcopac.6j
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 pacman.5e
-rw-r--r--  6.3 unx     4096 bx defN 96-Dec-24 23:32 pacman.5f
-rw----     2.0 fat     4096 bl defN 96-Dec-24 23:32 pacman.6e
-rw----     2.0 fat     4096 bl defN 96-Dec-24 23:32 pacman.6f
-rw----     2.0 fat     4096 bl defN 96-Dec-24 23:32 pacman.6h
-rw----     2.0 fat     4096 bl defN 96-Dec-24 23:32 pacman.6j
-rw-r--r--  2.3 unx      933 tx defN 04-Mar-18 23:31 readme.html
15 files, 42693 bytes uncompressed, 23761 bytes compressed:  44.3%

Ok. Most likely the cause is UNIX style zip archive (unx).

Solution:

1. Unpack all of mixed fileformat zip archive
2. Repack with zip --DOS-names -j <zipfile> <files to archive>. Or short -k and -j as options.
3. Check again:

$ zipinfo pacman--DOS-names.zip
Archive:  pacman--DOS-names.zip
Zip file size: 25623 bytes, number of entries: 14
-rw----     2.0 fat       32 bx defN 96-Dec-24 23:32 82S123.7F
-rw----     2.0 fat      256 bx defN 96-Dec-24 23:32 82S126.1M
-rw----     2.0 fat      256 bx defN 96-Dec-24 23:32 82S126.3M
-rw----     2.0 fat      256 bx defN 96-Dec-24 23:32 82S126.4A
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 NAMCOPAC.6E
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 NAMCOPAC.6F
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 NAMCOPAC.6H
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 NAMCOPAC.6J
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.5E
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.5F
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.6E
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.6F
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.6H
-rw----     2.0 fat     4096 bx defN 96-Dec-24 23:32 PACMAN.6J

4. Note the UPPERCASE ("8.3" filename.extension limit) and fat only zip entries.
5. Copy/rename to the target folder/target name.
6. Start your game.
7. Enjoy!

Remark: If you organize/rezip your roms solely on Windows you probably won't run into this.

HTH