Also we can check via this trick as well - You can start by going into Admin / Upgrade Wizard, and running the first step, that will check some permissions (but not all). Don’t worry, it won’t upgrade anything unti lyou give it an upgrade package, and you can just cancel before that.
… that is all very fine, but none of your methods will really check permissions problems completely.
I use this command to see all files with permissions and owners:
tree -iupf .
Normally I “grep out” everything that is owned by my web server user:
tree -iupf . | grep -v www-data
It will say something like 3329 directories, 14955 files, that’s ok, but if it lists files or directories owned by any user different from www-data, watch out.
This is for ownership checking, but you can also pay attention to the permissions of course.
The really tricky part are systems that are not working because they lack the SetGID bit in the directories under which the system tries to create new directories (typically “upload”). This is only problematic on some systems, on others it works fine without it.