Hello, and welcome to gbatemp

I will (try to) explain how to setup and use EmuNAND with USBLoaderGX. (you already found some, but maybe they are old, or not well explained).

Creating and using EmuNAND with USBLoaderGX
cIOS - Neek - Neek2o​

So, before doing anything, you need to know that there are two different emuNAND modes.
The first one is done by the cIOS which redirects some NAND file access to SD or USB. We call it "cIOS EmuNAND" mode.
The second is done by Neek which fully redirects ALL the console and chipset access to SD or USB. We call it "neek" or "neek mode"

cIOS emuNAND is very simple and easy to setup and use, faster to boot and exit back to the loader, but doesn't have 100% game compatibility. Mostly N64 games and few Wiiware are not working. Seeing you tried to play N64 games you probably did well in wanting to use neek for your first try.
Neek is not too much complicated to setup, but requires some additional steps to create the needed files that will be responsible for the NAND redirection.
both cIOS and Neek emuNAND can share the same emuNAND dump, so it's easy to switch from one or the other


USBLoaderGX is now compatible with Neek emuNAND, it can boot into neek mode without the need of NSwitch homebrew or a NSwitch channel to boot into neek, or bootmii files, etc.
but you have to use latest release : as of writing it's 1260 (There's a new version available!). for latest, check my signature, or the official thread's first page, or sourceforge.

If you are using USBLoaderGX channel, be sure it's a forwarder channel or you'll be launching r1180 instead of 1260 (get the new one), and you won't have neek support.
if you have a full channel, follow this tutorial to get the forwarder channel.


Dumping NAND and using cIOS EmuNAND
There's nothing easier!

- be sure to use d2x cIOS v8 or newer in USBLoaderGX (or you can use IOS58 if you don't have cIOS installed, but only "Neek mode" will work, so all the cIOS mode games can't be launched)
- launch USBLoaderGX and go to the settings>user path, to edit your path if you want. you need to edit this setting : "EmuNAND Channel folder"
- go to the settings>features menu, select dump NAND>full (it will ask you where to dump if "emuNAND channel" and "emuNAND save" paths are different, choose "channel")
Dump done.

- go to settings>loader settings>emuNAND channel : FULL (do not use partial)
- go to the main screen>4th icon in the top menu>enable EmuNAND.
Setup done

you just created and displayed games located on emuNAND. You can now launch the titles or games.
They will use cIOS mode to redirect NAND to emuNAND, and will require d2x cIOS for that.

Adding new channels
USBLoaderGX has a WAD manager for emuNAND.
- put your wad file on SD or usb
- launch the loader and go to settings>features>emuNAND Wad Manager
- select if you want to install a single file or batch mode to install all files from a folder.
- select your wad file or a folder and choose "install"
done


Compatibility
The steps above are using the cIOS emuNAND mode.
Like I said, compatibility is not 100% but you should use this mode whenever you can. It's faster to boot and can exit back to (return to) USBLoaderGX if you have a USBLoaderGX forwarder channel installed on your NAND and "return to" option pointing to that forwarder.
This mode is a mixed of realNAND and emuNAND : the system menu and the console is still running on real NAND, the IOS are loaded from realNAND but file's access are redirected to emuNAND. When you exit a game, it just stop redirecting file access and reload system menu or the forwarder to go back to usbloadergx.


If you encounter some games which don't work, you will need Neek mode.
Neek is rebooting the console in a full redirection mode. Everything is loaded from the EmuNAND path : the system menu, the IOS, the settings, etc.
The console does not know it's currently doing a redirection, as IOS are not redirecting anything and all official IOS are used instead of cIOS to load games.
the SD card and USB device are locked and can't be used (no homebrew or forwarder access!).

To use neek mode, you will have to add some files to your device:/sneek/ folder
They will be responsible for redirecting all the NAND to your emuNAND path and adding new features (game patch, menu patch, region free, etc.)


Neek or Neek2o
• Neek (Sneek for SD or Uneek for USB) is the main program.
• Neek2o is a modification of neek done by another developer. This one adds new features like:
- subfolder support : you don't need to put the NAND dump to the device's root.
- multi-emuNAND support : you can keep multiple NAND dump and select which folder to use. (easy to keep one PAL, one NTSC etc.)
- Autoboot at launch: you don't see the emuNAND system menu screen and don't need to select the channel to launch,
- return to: you can choose to reload a different channel on emuNAND instead of reloading the emuNAND system menu,
- Wbfs support: you can boot wbfs games from usb:/wbfs/ folder.


Wii and vWii differences:
Neek2o r96 is the latest released version and works only on Wii.
Neek works on vWii (a special vWii version has been released)
Neek2o doesn't have an official vWii release, but a leaked (and illegal to share) version is floating around. that version is precompiled and only need to be placed in /sneek/ folder.

Neek(2o) setup
I already wrote few neek and neek2o compiling and setup tutorial, so I will give links instead of writing the same thing again.

Neek/Neek2o Wii file creation using modmii (skip step 1 and 2)
Manual neek/Neek2o Wii file creation (if modmii doesn't work)

JoostinOnline also wrote a guide to compile Neek (not neek2o) for wiiU's vWii mode : http://www.hacksden.com/showthread.php/8119-Compiling-a-vWii-compatible-version-of-SNEEK

Once compiled, and the neek files copied to the devices (sd and/or USB) you can continue reading this page to setup USBLoaderGX with neek.

Adding a way to exit back to RealNAND.
When in neek mode, all the console is in redirection mode. When you exit a game, you are back to System menu, but it's not your REAL system menu, it's still the redirected one. There's no way to tell the console to exit back to realNAND (as it already think it's the real nand).
The only way to exit this mode is to reboot the console.


Wii
Nswitch channel can detect if you are already on neek mode and instead of launching neek again it reboots the console (reboot<->neek), so we will add this channel to your emuNAND. It will be useful later to automatically exit emuNAND when exiting a game in order to go back to USBLoaderGX located on realNAND.
The Nswitch homebrew has been created in different channels. only the visual is different, so choose based on your preference. (but remember that you will rarely see it, so any channel visual will be fine)

- put one of these 4 wad files on sd or usb. I recommend the classic visual "neek2o NK2O_1 .wad"
- launch usbloadergx and install the wad to your emuNAND.


Note:
If you created a new clean NAND using modmii, you have the option to automatically include a "neek2o" or "Nswitch" channel which will be used to exit to realNAND. The channel will have the correct TitleID (NK2O) so you don't need to install any other wad.


WiiU vWii
vWii already has a "console rebooting" channel : return to WiiU.
you don't need to install a Nswitch channel.


booting neek mode
If you want to boot into neek mode, you have different possibilities:
- right at console boot : using modmii @ boot2, you can autoboot into neek.
- right at console boot : using priiloader rebooting into bootmii or autobooting nswitch.
- manually booting nswitch channel or homebrew
- using a loader : USBLoaderGX can boot into Neek system menu OR tell neek2o to autoboot a specific game bypassing the system menu loading and patching process.

we will use the latest method as you asked how to use it with usbloadergx.
Additionally, USBLoaderGX is fast booting into neek, it doesn't rely on bootmii files or nswitch.

if you followed the install guide linked above, you should now have this setup :

On your device where emuNAND is located:
/nand/my_emuNAND/ <-- your emuNAND path
/sneek/kernel.bin
/sneek/font.bin
/sneek/di.bin <-- if you want Disc emulation (playing wbfs games from the disc channel)


First launch, or Neek system menu launch
We will launch Neek system menu once to verify it's correctly working. No auto-booting a game yet. it's also done to generate the needed files if you just made a clean NAND from scratch using modmii. in that case, the first launch will take few minutes on a black screen before asking to setup the day/date/wiimote sync, don't worry!.
- launch USBLoaderGX
- go to settings>Features>boot neek
wait for neek to boot, it should load the System menu like if you were on your real Wii, but it's actually loading all the data from EmuNAND. the channels you added on emuNAND will be displayed. You can now launch them like if they were on your real Wii.

launching neek this way lets you setup neek and launch game discs from the disc channel.
Press 1 (or 2) on the wiimote to display hidden menus. You can navigate with +/- and A/B button.
Set region free ON and select the proper video mode you want to use inside neek emuNAND.
note: region free is sometime not enough and you will need a NAND from the same region than the game you want to play. you can store multiple NAND dump:
/nand/PAL/
/nand/US/
/nand/JP/
the used path will be set in USBLoderGX, or can be switching from the neek2o hidden menu.

To boot a game, select its channel or use the hidden menu to mount a game disc and launch it from the disc channel.
to exit neek, load the NEEK2O channel you installed on the previous step (nswitch channel), it will reset the console.

Autobooting a game in neek mode
Autoboot is possible only with neek2o.

You should use neek mode only for games not working with cIOS mode (unless you really like staying in neek mode all the time) so you set the neek option only individually in USBLoaderGX.

select a game requiring neek (for example N64 games or Castlevania rebith), go to settings>game option>emuNAND mode : Neek
Select if you want to enable "return to" to reload the NEEK2O channel when exiting your game to initiate a reboot to realNAND.

you can now launch your game !


If you want to stay in NEEK mode to launch another game, disable "return to".
If you want to use neek mode for all your emuNAND, set this mode to the global setting :
settings>loader settings>emuNAND Channel : Neek
settings>loader settings>return to : if a channel is selected, it will return to NEEK2O channel, to disable it just empty that option. (not the best way, but it's like that for the moment)


Ok, I think I completed that guide now!

 

I'm glad I could help you.
I hope this guide can help a lot of users (I spent some time writing it, haha)

if someone see any issues or needed addition I can edit the guide to make things easier or more complete.
There are things I didn't mention on purpose to keep the guide easier to understand, but there are more things which can be done, like multi-emuNAND (PAL+NTSC) displayed at the same time in USBLoaderGX.
There are also cIOS emuNAND fixes for incompatible games, as neek mode is not always needed, but it requires more knowledge with IOS and neek is easier to setup instead for some users.
I also didn't link to vWii Neek (I will add it later)
I can add more detail in another post to prevent providing too much info in the main guide.

 

the d2x installation package for Wii doesn't contain any wad file, unless you followed an illegal tutorial...

v8 are working fine and doesn't have different compatibility than v10. You don't need to update.
cIOS are irrelevant when using NEEK mode, as NEEK only use official nintendo IOS, not custom IOS. so installing d2x to get neek is not even needed and would have no effect in the compatibily.

If games are hanging on black screen, it's probably a wrong setup (video mode? region ?) or still using full instead of neek mode.
"file is corrupt" message is either because you use FULL instead of NEEK mode, or if you use neek it's then the wrong region (or your game is just bad dump)

 

Glad you got everything working now. But should I update my guides in any way to make it more easier to follow or understand which files are needed?
which point were not detailed enough?

 

These are not needed if you use USBLoaderGX to boot into neek.

they are probably used if you boot into neek by another loader ? wiiflow maybe ? because usually, homebrew are named "boot.dol" when used from HBC, so using this name is either because it's used by another loader or has to be renamed to something else before being used.
you can safely delete them if you use USBLoaderGX only.