@sylvain_merle have you managed to get the phone started again?
If not did you install before the update something like Xposed or OpenGapps?
If you did you first need to go to Recovery Mode (TWRP) and reinstall those as well.
If this is not the case but you still have problems, even after checking the battery try again to get into Recovery Mode and install the update manually with the link @Lidwien gave in the first post.
Where can I find the sources corresponding to this release?
When I follow the official build instructions, I can see no tags for this 17.09 release.
Also, the latest commit on the Kernels fp2-sibon Branch seems to be from March, but I think at least for fixing the BlueBorne issue there has to be newer changes?
Hi, could you please confirm, did you upgrade 5 to 6 through the Updater app, and retain your user data?
I want to do that with an encrypted FP2, not using xposed or opengapps that I think people had problems with, but I’m still worried about losing all my data.
17.04 seems to be unstable as I have random reboots, even when the device is asleep on my desk.
I did the upgrade from Android 5 to 6 with an earlier version (Android 5 to 17.08 maybe, you’ll find my comment in the forum somewhere) some months ago. The upgrade I’m referring to in this thread was starting from the previous Android 6 version (i.e. version 17.08.something).
Probably not what you wanted to hear, sorry…
Thanks, seems like here you said you made that upgrade. I think I’ll give it a shot but still going to look at how to back up my phone just in case…
I am currently running FPOOS 17.06.4. Is it safe to upgrade directly to the latest versions without going through the previous ones?
Yes, it is safe to do so 
Fairphone Open 17.10.1 is now available 