You can add your own extra operating systems to the Berryboot menu. However this requires that you convert your file system image to SquashFS format first.
Most Raspberry Pi operating system images are disk images containing two partitions. A FAT partition with the boot loader and kernel files, and a second ext4 partition with everything else. We are interested in the second partition.
With a regular Linux desktop computer that has kpartx and mksquashfs installed, you can convert the second partition to SquashFS like this:
$ sudo kpartx -av image_you_want_to_convert.img add map loop0p1 (252:5): 0 117187 linear /dev/loop0 1 add map loop0p2 (252:6): 0 3493888 linear /dev/loop0 118784 $ sudo mount /dev/mapper/loop0p2 /mnt $ sudo sed -i 's/^\/dev\/mmcblk/#\0/g' /mnt/etc/fstab $ sudo mksquashfs /mnt converted_image_for_berryboot.img -comp lzo -e lib/modules $ sudo umount /mnt $ sudo kpartx -d image_you_want_to_convert.img
Put your SquashFS formatted image on a USB stick, go to the “Operating system installer”, hold down your mouse button over “Add OS” and select “Install from USB stick” If your image prefers to have a certain memory split use the extension .img128 .img192, .img224 or .img240 instead of .img.
If the image you are converting is based on Debian/Raspbian delete the etc/console-setup/cached_UTF-8_del.kmap.gz file before converting the image to force regeneration of the cached keyboard mapping on first boot. This is to make sure it uses the keyboard layout set in Berryboot instead of default British.