I've had the n900 since early February. I came over from many years of using Palm Treos. I'm fairly satisfied with the n900 and look forward to installing the new update. I build my own home computers and am the guy my friends and relatives turn to with their computer problems. But I know nothing about Linux. In fact, when we were expecting this update to come about a month ago, I couldn't even follow along with the instructions found here and on the wiki to free up the required rootfs space. I 'gained root' and entered in the commands, but got only error messages for my attempts. So, after uninstalling any programs that seemed to be taking up decent chunks of space, I've only gone from 15MB free to 25MB free at present.

But I'm not here to ask about rootfs. I want to do a fresh install/re-flash of the newest 1.2 OS. And I promise to be more selective in the future when browsing the testing and extras depositories.

What I'm worried about is losing data from programs I plan to reinstall after starting over from scratch. Certainly, I want my text messages, photos, calendar events and contacts to be restored. But beyond that, how can I back up the data files for things like:

Notes
Angry Birds scores
Extended Call Log
fMMS messages
Fuelpad (car mileage history)
Series Finale

I've done a back-up of the phone resulting in an 8MB file. I guess my next step would be to find that file and copy it to a computer. And then to sync my contacts and calendar with Outlook. Then use a computer to look for those data files mentioned above on the phone itself. Finally, I'd flash the n900. But, as you can guess, I'm kinda worried about finding those data files. I doubt they'll all be in their own nicely labeled folders just waiving 'hello' to me.

So, assuming I find that my plan above isn't going to work, I would then uninstall every program I don't use (and maybe even those I do if they don't keep data files that I want to save) and perform the upgrade. I suppose that's about as close to a 'fresh install' as I can get without giving up the data files listed above.

Before I start, though, I'm hoping someone here will be willing to advise me. Just let me know if my logic is flawed. Is there's no way to do a full reformat and still get my fMMS, SMS, Angry Bird scores and fuel mileage history restored later? If not, will doing an upgrade without a full re-flashing/wipe still leave my rootfs in the sorry state it's in now?

Thanks so much for reading this. I've read a lot of topics on flashing/upgrading, but the closest I've found to my specific concerns are about saving SMS conversations. And, sadly, it seems the full format way of doing things doesn't appear to leave any way of restoring our text message history. I hope my understanding of that subject is all wrong.

Fuelpad's database should be in your backup but if you want to be absolutely sure, you can find it as /home/user/fuelpad.db. This file name is actually shown in the Settings dialog.

1.
The user configuration/user data files for various programs in Linux are stored in files or directories that start with a dot and are located in user's home directory (system-wide configuration and data is elsewhere, like /etc)

For N900, that is: /home/user

These files can be listed with "ls -a"
I'll give you the commands to make a full archive of /home/user that excludes MyDocs, which is a folder that you see when you connect the phone to a Windows computer.

cd /home
tar czvf user/MyDocs/user.tar.gz -X user/MyDocs user

This means:
Go to /home
Archive directory "user" into file user/MyDocs/user.tar.gz, verbosely, with compression and exclude the directory user/MyDocs

You will see this archive in MyDocs and can copy it to your computer. The contents can be seen with 7zip in Windows.

Later edit: I've run the command myself and I see that the -X option from the tar of busybox is a bit more primitive and doesn't do what I have intended. That is, it doesn't exclude user/MyDocs from the archive. This means it will make one big file with all your music, images and what not. And you'll have to have more than 16 GB free to be able to make a complete archive. This option should work as intended with GNU tar. I think that GNU tar is available in extras-devel.

Now, rereading my message I realise that I might have confused you even more. I'm really sorry, I think the best option for you is to make more room in rootfs:

2.
To make space on rootfs, it should be enough to disable all other repositories, except Nokia Updates. I went from 84% to 75% just by doing this and I didn't need to uninstall any application.

Just a quick update from the original poster:

Thanks for both replies. I've followed all of the suggestions so far.

For anyone else that follows those instructions, I'd recommend moving your movie and music files to a computer before trying the archive command above. It appears that all of my MP3s and MPEGs are currently being archived as a result. It's been running for an hour so far and I'm getting worried what will happen if/when it runs out of internal storage to compress to...

Still, when it finishes, I'll be sure to run that same command again without my media files being involved. It brings great peace of mind to have this backup done before proceeding with the upgrade to 1.2.

Also, after disabling the other repositories, I only have 38MB free on rootfs. It doesn't seem you feel it's necessary for me to do a full reformat before flashing the upgrade. So, if that's not enough free space, I'll uninstall all the stuff I don't use anyway and hope that creates enough room.