Thread: Booting from MMC on N800 Now Available!!
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DCr33P is offline DCr33P
2007-02-28 , 17:13
Posts: 150 | Thanked: 3 times | Joined on Jan 2007
#119
Ok, I will try to answer as much as I can:

If I were able to boot from the MMC, would this still be the same as booting normally and then using the apps loaded or does this boot me into a special mode?
It's like having two different operating systes. The one OS (the original) is stored on the internal 256 flash memory of the device. The other one is the cloned system from your flash, stored on mmc/sd. From the moment on, you clone your original system from flash to the mmc/sd card, you will have two identical and seperated systems. Then you can choose from the menu of the bootloader which one you want to start. Changes on the first operating system do not affect anything on the other one. The other way around, too.
Installing an application on the OS on the card leaves the internal OS untouched. One can interprete that "special mode" is the abillity to install as many applications as you want(...and can fit on mmc/sd card), to have faster system and to have superior backup/restore possibilities.
Backup would be very easy:
- Put your card in a card reader and copy the whole ext2 partition to you desktop machine. When something went wrong, just copy it back.
OR:
- mount your rootfs on your card to a second mountpoint and copy the whole mountpoint via tar/rsync through a ssh connection(or smb share/ NFS) remotely to everywhere you want.


I would assume that the Bootloader would reside on the MMC and facilitate this booting. Is this correct?
The bootloader is not on the mmc card, it's stored on internal flash.
Is it stored on /dev/mtdblock0 ???

I heard somewhere, here I think that Nokia will release an upgrade to the current OS version in a few weeks. If so, I may try the "boot from MMC" option and this way, if I brick my N800, I have no worries, as I can just upgrade the system. Does this make sense?
You can't brick your system with this dualbooting story. IMHO, the worst thing that can happen is that the flashing process of the bootloader goes wrong. But then, you can always reflash with the standard bootloader, theoratically. You will not loose any data. If everything works and you boot from SD-OS, then even flashing is not nessecarily, since you can easilly recover the whole system if you broke your OS. The chances that you ever definitlely brick your device are very very very very very low, unless you mess up with one of the early "bootloaders" of the system. But I think nobody did this...
If you brick your OS on the flash, then you can simply reflash. If you brick your kernel, you can simply reflash just the kernel...
Have to admit that I have never done this, cause I have not bricked my device, so far. But I got it only for 2 Weeks... the time will come... but that should be no big deal

By the way, I am using a Mac so I am not sure if some of these tools are compatible, or do I need a Windows/Linux box to try this?
I am using linux all the time, so I don't know how those WIN/MAC tools behave. A Linux Live-CD can solve all you problems, if you don't like to install Linux AND DUALBOOT

I hope I could answer a few points, since I live in Germany and there are only basic school-english-skills left, I hope it's understandable