Notes for myself to remember...

Replacing AOSP gallery (Gallery2) with GalleryGoogle

Say you don't want to reflash the whole device just to get a more recent gallery app (e.g. you happen to install CM and old-ish gapps on top). Fix is rather simple:

1. Go here and download the proper stock package
2. Check ZIP for optional/gallery. I found the following interesting
   • lib/libjni_*.so
   • mako/app/GalleryGoogle.apk
   ...copy those on your device.
3. The following happens on the android machine:

       mount -o rw,remount /system
       rm /syste/app/Gallery2.apk # or whatever was the name
       cp /sdcard/stuff/lib* /system/lib
       cp /sdcard/stuff/GalleryGoogle.apk /system/app
       chmod 644 /system/lib/libjni_*.so # better only put the .so's you copied here, to be safe
       mount -o ro,remount /system # be safe
   

4. Reboot android. Most probably your gallery app is gone. Just reinstall the apk you copied. Didn't yet check how the apk registration works in android so...... :)
5. Voila, photo sphere and friends work now

Manual disk mount in Android

...should work similarly to linux. E.g. using the busybox mount binary:

mount -t vfat /dev/block/sda1 $mountpoint

Attention: the devices appear under /dev/block, instead of just /dev!