Virtual SD Card Guide

Dolphin can store data to a virtual SD card named sd.raw. It is stored under "%userprofile%\Documents\Dolphin Emulator\Wii" for Windows. By default, it will be created with the size of 128MB.

The virtual SD card is very important for homebrew apps on Dolphin. Project M and Mario Kart Wii custom tracks are the best example of this, as some homebrew apps can only work using files stored on the SD card of the real hardware for which they were designed.

Easy Dolphin SDCard Maker
If the sd.raw does not exist or you prefer to start over from scratch with size more than 128MB, you can create sd.raw using Easy Dolphin SDCard Maker. It is recommend you create one with size at least 512MB for large homebrew apps, for example, Project M, and no more than 2GB for best compatibility as there are compatibility issues with some homebrew apps trying to run under an SDHC card on the real hardware.

Windows
The sd.raw file can be edited using WinImage.

OS X
In the Terminal, type the following to mount the SD card:

hdiutil attach -imagekey diskimage-class=CRawDiskImage ~/Library/Application\ Support/Dolphin/Wii/sd.raw

The SD card can then be ejected through Finder when done being edited.

Linux
The sd.raw file can be edited by mounting it to a virtual disk:

mount -o defaults,umask=000 sd.raw /media/sdcard

When you are done, simply unmount it like this:

umount /media/sdcard

Dolphin Setting
Go to Options > Configure... > Wii > and enable Insert SD Card.

Usage with Homebrew App
The external files used for the homebrew app must be stored within sd.raw and the homebrew app itself (boot.elf or boot.dol) must exist outside of it for Dolphin to load. Project M, for example, will load from SD root \projectm\ and Dolphin will need to launch Project M through \homebrew\apps\projectm\boot.elf, NOT in the virtual SD card. It is very ideal to have same copies paralleled between inside and outside of the virtual SD card, so you will have nothing to lose.

The homebrew app that was programmed to hack the Wii game will not work if you haven't set a particular Wii game as the default ISO! Within the Dolphin game list, open context menu (right-click) on any Wii game and click Set as default ISO. Do this before loading a homebrew app with Dolphin.