I could finally trace how IOS0 (detected by HackMii installer) is being created!
This point was brought out on an old thread, but I decided to create a new one instead of brining a death thread back.
The answer is simple: It is created by DOP-Mii v <= 13 whenever you install a IOS.
I have not tested v14 to see if it also creates it or not. I don't think I will test for that anytime soon, since testing is not trivial. I restored an old NAND backup I had and I ran HackMii installer to get a report on all installed IOS and see if any was patched. The report didn't find IOS0 installed. Then I started running one by one every app I had ran that might potentially have created it.
I used DOP-Mii v13 to restore trucha bug on IOS36 and then I ran the HackMii installer again, then the IOS0 was there. I thought that maybe this only process (which involves downgrading IOS15) created it, but I noticed that the HackMii installer log reports the IOSes in descendent order of when they were installed/updated. IOS0 was at the top.
Then I uninstalled BootMii as IOS, and installed it again, the report now showed IOS 254 at the top, and IOS0 below. After that, I ran DOP-Mii again and patched and installed an IOS in slot 205. I exited and loaded HackMii installer again. The order was this: IOS0 at the top, then IOS205 (which I had just installed) and IOS254 in third. So I concluded IOS0 is installed/updated everytime you install an IOS with DOP-Mii.
So for all you guys wondering where IOS0 came from, now you have your answer.
I really wish that somebody could confirm if DOP-Mii v14 still creates it, since I don't know if it is created only when the IOS installed gets patched, or if it also creates is with any vanilla IOS installed. Also, since DOP-Mii v14 does not use a patched IOS anymore to install/uninstall IOSes, I don't know how it accomplishes this purpose.
Disclaimer:The reason of this thread is to provide relevant information to advanced users regarding the results of a test I conducted in order to trace the origin of an IOS file which have been reported several times.
This post has no intention of providing information on patching IOSes, nor any use that could be given to them.
DOP-Mii as of v14 is now supported again in WiiBrew forums, so I am entitled to discuss about this app as long as I do not provide any instruction on how to patch or make use of a patched IOS.