XF 2.2 Upgrade from 2.1.11. to 2.2.0 failed - "not all files are writable"

[Lemkonen]

I run a small forum with a couple hundred members and posts. The web upgrade failed with the message:

Oops! We run into some problems.
Not all files are writable. Please upgrade manually.

Is there a log which files are not writable? Is there a way to fix this or is going manually / CLI the only path forward?

 

[briansol]

Make sure writable directories (like cache, avatar, etc) are chmod 777 during the upgrade. put them back to 755 after, or even 644 if your server will be ok with that

 

[Ozzy47]

All the files need to be writable by the user PHP is running as - as the update may change any file.

 

[Donske]

I have the same error. I also have a 'backup of my site' (mirror image) running as well - it upgraded the backup site with no problems. I am very nervous about doing any manual upgrade.
I have never had this problem before
Thanks