This isn’t really a full HowTo. They’re more like my own notes for future reference, for myself and hopefully for others as well. Instead, I link to already available material, but make annotations for some customizations that I made.

This HowTo describes the steps to take in “dual booting” on the N810, that is, booting from a flash card.

1. Why dual/multi-boot?

The Maemo wiki cites a few reasons why. The main reason why I decided to dual boot was space. I really wasn’t using the internal 2GB flash memory and I have no use of GPS at the moment. And since Marijn’s KDE packages would be taking up more space, I decided to use the internal memory as my “main partition”. It will probably be useful for future KDE development as well. (Note: Marijn says that the packages were broken, so I wasn’t able to install them fully at that time)

2. First, gain root powers

To be able to perform any of the next steps, you need to have superuser access. The Maemo wiki presents three ways to gain root access. I was advised to use the openssh method. This way, I hit two birds (root access and ssh) with one stone.

Maemo wiki: Root access

3. Split the card

I’m not sure if this step is absolutely necessary. But since the N810 uses the internal flash memory for virtual memory (swap) automatically, I think it’s a good thing to do so anyway.

IMPORTANT: Be sure to backup your data on the internal flash memory as partitioning and formatting will completely erase anything in there.

Oh, and turn off virtual memory in the Control Panel first.

Partitioning might be a bit daunting if you’re not used to command line partitioning tools like fdisk and sfdisk. But the guide in the wiki is very simple and straightforward. The most confusing part is trying to remember which device node (under /dev) stands for which flash card. Just remember that mmc*1 is for external. anything else (mmc*0 and mmc2) are for internal.

Some other notes:

• The first partition’s starting cylinder is always 1.
• The next partition’s starting cylinder is 1 more than the previous partition’s end cylinder
• To compute the number of cylinders for a given MB size, I used the formula numCylinders = sizeMB / 0.032 or numCylinders = sizeKB / 32.

Since I wanted to split the card in half, but giving more space for the cloned system, I gave around 29,000 cylinders to the first partition, leaving the rest to the second partition. The sfdisk step looked something like this:

sfdisk /dev/mmcblk0
/dev/mmcblk0p1:1,29000,6
/dev/mmcblk0p2:29001,,

Maemo wiki: Partitioning a flash card

4. Attack of the clones

This last step was the most complicated in the process, but even that is made easy by a lot of ready made scripts. It would be best if you had your Maemo browser open to the wiki page so that you can just copy the wget commands instead of typing them manually (which I stupidly did).

I followed the guide to the letter except for the following:

• I didn’t configure the bootmenu options at that time (see below for more information)
• Since I was using the latest Diablo version, I used immc2 for the device name in the Set the default boot device step.
• I also didn’t remove the menu (last step)

Maemo wiki: Booting from a flash card

5. And finally…

Everything went well and I was booted into the clone system on the internal flash card in no time. Now for some final tips:

• Don’t forget to re-enable the virtual memory
• Don’t be worried if the memory usage reported for the Device is almost twice as big as on the original system. I was told that this is because the flash card is not compressed, unlike in the original um… memory (what is the technical name for that? RAM?).
• I found that the 30 (or was it 20?) second delay for the boot menu was too long. I wanted to shorten that time, like you could when using GRUB. You can edit the bootmenu.sh file in /mnt/initfs/. However, that mount is read-only, so you have to remount the thing with this command: mount -o remount,rw /mnt/initfs/. Look for the MENU_TIMEOUT line and set the number of seconds that you want.

Enjoy your cloned system and extra space!