Notes for myself to remember...
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:
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
...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!