Ubuntu is the best PC OS to use while reflashing.

Overclocking is not particularly risky.

Undervolting too much can cause crashes that are easily cured by undervolting less.

In your case, it looks like some files got corrupted -- flashing is often the easiest solution.

The state of the battery charge is a critical issue. If you can't be sure you have fully charged batteries, you should buy a cheap separate charger and some cheap batteries. Untold misery has been caused by trying to flash with low batteries. Everyone should have a separate charger anyway.

Thank you so much for offering help!
I succeeded in flashing rootfs, I'm soooo glad the battery didn't bail on me!
All my data in mydocs is still there - now do I still need to reflash eMMC?

I restored my my list of apps and settings from backup. Everything seems fine, except UI is a bit jerky. I don't remember though if that's just how the N900 came to me 16 months ago, and I had smoothed things out wit swappolube etc, or if it's actually supposed to be all slick and quick right after a reflash?

Now to avoid this happening again, it seems to me Estel suggested that a problem might have been caused be preset lower voltage profiles? If so, is there any alternative for a non tech-smart user (i.e. I won't be able to fiddle with the settings finding my own perfect profile...)
Thanks for any help offered!

I found QCPUFreq to be very useful for overclocking on a per session basis. I played around with the persistent OC settings, but found them slightly unstable on my machine, although many others have reported no problems whatsoever. QCPUfreq does require a power kernel, if I am not mistaken.

Hey bennypr0fane, sorry for late answer (I accidentally didn't subscribed this thread).

I'm glad You get Your N900 working again. As for flashing eMMC, it's not necessary in most cases. Ho ever, cause You're not sure about problems origins, and You were using undervolting, I would do full reflash with vanilla eMMC, just to be on the safe side (better than sorry ). I can't agree with geneven, that undervolting is "easily fixed by undervolting little lower". It may be, but its also possible, that small filesystem corruption will result in something screwed later - maybe weeks or months after incident - and You'll have no idea what the hell happened.

Of course, it's only valid if Your problems were really caused by undervolting, which is pure guesswork. Anyway, reflashing with eMMC is described (with details) in Wiki - just remember, that it takes much longer than rootfs reflash (not to mention kernel only), so don't panic and don't abort it after minute or two

As for undervolting, its touchy subject. People claims that it impacts battery life (positively) really, which, personally, I doubt. At least, no one was ever capable of bringing here real, measured quantities, instead of "perceived" observations, which may be as good placebo effect.

One time in the past, I encountered thing that I'm 100% sure was cause by slow, long-term filesystem corruption, caused by undervolting (nothing extremal, just ideal profile). That was only one case, when I had to reflash, by the way. Examining titan's profiles, I noticed that voltages seems to be adjusted in little *no* logical way - if we have in mind characteristic of frequency/voltage adjustment/power leakage ratio (things beyond scope of this post). Long story short, I just re-created them, using common logic and sense (most important), Nokia stock settings + titan's settings (setting something in between, but again, use common sense about adjusting voltage - more You're up, compared to default max frequency, the more voltage difference between steps You need - it's *not* linear growth, like most of the times, in titan's settings...).

I also mentioned BackupMenu - it's great little package, that helps You creating *exact* tarballs of You root and opt fs images, so, You can revert to last working state of machine, or even bring it back to such a state after full reflash, in few seconds (except for power kernel installation, which always must be done manually, after vanilla reflash). Just search forum for "backupmenu - OS backup and restore", and You're good to go

I hope this post wasn't too chaotic - it's little late here. Hope it helps.

Hey, my N900's still not 100% back to normal - it can wait since I got a C7 to replace the phone functionality, but I'm starting to miss the real thang ;-)

So, after escape from reboot loop, I reflashed eMMC too, after which battery life went back to normal. I installed CSSU, portrait desktop, speedpatch and some apps, no OC. Everything seems fine, except:

The file system looks really strange, as in, there is next to nothing in the MyDocs folder!
More precisely, it looks like this, not like this
That's not normal, is it?

I would be careful with "speedpatch", due to "headless chicken" behavior. I mean, that it contain so much various tweaks - some of them undocumented, some obsolete probably - not tested to work with new kernels, CSSU etc (from time they've been created), that most of the time you have no idea what any of contained path is doing.

It's better to apply patches one by one, and only, if You - at least partially - know what this script is meant to do (technically, not theoretically). Personally, I don't use speedpatch, cause IMO wise tweaking step by step gives better result

Also, while I held respect for Karam due to his hard work on documenting "hacking" packages and ways of using it, I don't see any reason why speed path should improve battery life (meritocratic told - technical iinfo), and it seems to me, that most "speed" things there are placebo effect.

What even worse, some of things there do same as "more trusted" tweaks (that do one/few thing at once, but do it as good as can - general linux philosophy) so You don't have idea what is overwriting what.

OC is also OK, if You don't go higher than 900 and don't undervolt too much. Also, stay away from smartreflex

so, if i remove the speedpatch, will it turn my file system back to normal?

Short answer:

I've no idea

Long answer:

It depends. If problems were caused by speedpatch, maybe - I don't know how good post-uninstall scripts of speedpath are. I would rather try with full reflash, kp, CSSU without speedpath.

Anyway, I don't know what exactly is wrong with Your filesystem. It looks ok, doesn't it? If You mean lack of some folder - like Camera - maybe You've not get any photos, and appropriate folder was not created yet?

Thank you for advice, Estel!

What do you mean by "kp" here?

No, that's not it. After eMMC being newly flashed, the pre-configured MyDocs folder should contain subfolders for Video, Music, Documents etc. as shown in the wiki, even if no files of those types have been created there before.
However, all the subfolders magically reappeared yesterday.
Instead, I found out that camera app doesn't show the captured image, just the UI controls in front of a black background (yes, with lens cover open). Will reflash - again, as advised.

Thanks for replying, Estel!

Glad to help, if it's any

By KP, i mean kernel-power. Latest version is KP48 and it works fine, ho ever, latest 100% stable is KP47. Definitely worth installing.

Looking forward to Your reports after reflash