I get permissions errors when I have a process running as root, spawning a subprocess as www-data, which then accesses a dir which is owned by root, with a subfolder which is owned by www-data, which has a symlink to a dir which is owned by a user in the group www-data, which then has.... YOU GET THE IDEA. How the heck do I know where it fails in this impossibly complex chain? All I get is Permission Denied
Without getting bogged down in the details of this particular situation, how does one begin to debug a problem like this on unix?
I want to just say
debug_permissions.sh www-data /my/long/symlink/chain``` and I want it to go through and tell me where the terminal point is (where www-data fails to have permissions) I know there is a tool ``` namei -l /path/``` but that isn't very helpful because it doesn't let me run as another user (or at least I don't know how) If I run ```sudo su www-data``` I get **This account is currently not available.** I want to be able to "become" www-data and "cd" around to the dirs and see where i fail to see things. But, that's not letting me do this and I don't want to create a new user just to do this.