Thanks for the response. So I guess what I really want is for the Dropbox container to run as root. Everything else on my server is running as root and creating downloaded files as root:root, and I've had no issues witht his. I have no personal information on my server and it's just movies, music and comic books, so I really don't care about the security implications of this.
If I were to run this Dropbox container under my non-root username, I would also need to move every other container over to that username. So my preference would be to just run this Dropbox container as root.
I tried this by entering DROPBOX_USER = root, DROPBOX_USERID = 0, DROPBOX_GROUP = root, and DROPBOX_GROUPID = 0.
I'm getting this in the log after activation:
usermod: user root is currently used by process 1
WARNING:tornado.access:404 HEAD /blocks/510013235/NV50NTkhIybNc_1--VF0mY4chlBSPeR7fQZwTf1bf4k (172.17.42.1) 678.61ms
WARNING:tornado.access:404 HEAD /blocks/510013235/NV50NTkhIybNc_1--VF0mY4chlBSPeR7fQZwTf1bf4k (172.17.42.1) 716.83ms
...
...
And so on, with a few thousand of those 404 errors.
...
...
Finally, the container dies with this at the end of the log:
/usr/local/bin/myinit.sh: line 14: 14 Killed su -l ${DROPBOX_USER} -c "/dropbox/.dropbox-dist/dropboxd"
So apparently the container doesn't like running as root, but I'm getting similar 404 errors (minus the first and last error) running as either "nobody" or my non-root UID, just because neither of those accounts has access to the files the other containers are putting in the Dropbox folder.