As of Mer 0.17testing10 we have an image that is fairly easy to try out on Nokia N900. This guide is for advanced users and there is NO WARRANTY. It might turn your N900 back into the crazy guy from this video or chew out your microSD, so be careful.
You will need:
* A microSD
* A SD/microSD card reader for your PC
* A Linux installation on your PC.
* A copy of a Mer rootfs for N900 (0.17testing10)
* A copy of the files in your /lib/firmware from your N900. This includes WiFi and Bluetooth firmware.
* PR1.0, PR1.0.1 or PR1.1 on your N900
* That you have installed fanoush's bootmenu (dpkg -i it and run 'Install bootmenu' application icon)
Instructions (must all be done as root):
* Partition your microSD to first partition being Linux and format it as ext3 using mkfs.ext3.
* Mount the ext3 partition on your PC, let's say in /mnt/mer.
* Make sure using 'mount' that your ext3 partition is -not- mounted 'nosuid' or 'nodev'
* cd /mnt/mer
* tar --numeric-owner -pzxf /full/path/to/mer-armel-n900-rootfs-v0.17testing10.tar.gz
* cd lib/firmware
* cp in the files from /lib/firmware from your N900
* umount /mnt/mer
* Make a file "mer.item" in /etc/bootmenu.d on your N900, containing:
ITEM_NAME="Mer (external SD, partition 1)"
ITEM_MODULES="mbcache jbd ext3"
* Reboot your device, have the keyboard slid out. A bootmenu will appear where you can select Mer with the cursor keys.
* Mer booting.. wait for touchscreen calibration step
* And then you can run through the first boot wizard
* And a non-accelerated Mer desktop appears.
* Watchdog handling
Of closed source blobs used in Mer (for N900):
* DSME (open source) with libcal (closed source) running from the Maemo5.0 rootfs
* BME running from the Maemo5.0 rootfs
* Firmware files for WiFi and Bluetooth chip amongst others.
Either way, I hope you enjoy playing with an alternative OS on your N900. Feel free to report bugs at http://wiki.maemo.org/Mer/Releases/0.17 and talk to us on #mer on irc.freenode.net if you'd like to contribute to Mer.
To shut down Mer, either sudo reboot or pop the battery.