Suddenly, Ubuntu Dropbox wants authentication and won't start

[eater]

I've been running Dropbox on my Ubuntu 18.04 desktop just fine for months. Today, I noticed the application had stopped, so I tried to start it again and it said "Authentication is needed to run '/bin/sh' as the super user." Whether or not I authenticate, it then goes into "Starting..." status forever.

I've tried removing the current installation and reinstalling, but that doesn't make a difference.

Here's the terminal output:

dropbox: locating interpreter
dropbox: logging to /tmp/dropbox-antifreeze-PZrvIR
dropbox: initializing
dropbox: initializing python 3.5.4
dropbox: setting program path '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/dropbox'
dropbox: setting home path '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94'
dropbox: setting python path '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94:/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/python-packages-35.zip'
dropbox: python initialized
dropbox: running dropbox
dropbox: setting args
dropbox: applying overrides
dropbox: running main script
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/cryptography.hazmat.bindings._constant_time.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/cryptography.hazmat.bindings._openssl.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/cryptography.hazmat.bindings._padding.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/psutil._psutil_linux.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/psutil._psutil_posix.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/linuxffi.pthread._linuxffi_pthread.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/linuxffi.fcntl._linuxffi_fcntl.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/linuxffi.sys.compiled._linuxffi_sys.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/cpuid.compiled._cpuid.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/linuxffi.resolv.compiled._linuxffi_resolv.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/tornado.speedups.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/linuxffi.gnu.compiled._linuxffi_gnu.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/posixffi.libc._posixffi_libc.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/librsyncffi.compiled._librsyncffi.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtWebKit.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtCore.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtNetwork.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtGui.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtWebKitWidgets.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtWidgets.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtPrintSupport.cpython-35m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/eater/.dropbox-dist/dropbox-lnx.x86_64-56.4.94/PyQt5.QtDBus.cpython-35m-x86_64-linux-gnu.so'

[Emanuele P.1]

Thanks @eater, I will try the same then! It's very likely that I had moved some symlinks in the Dropbox folder just before.

[ceebeelee]

I had this too, under Ubuntu 18.10. I tried uninstalling/purging nautilius-dropbox and reinstalling from their web site. I tried deleting symlinks in ~/Dropbox. (both of these are solutions listed elsewhere). Neither helped. The following solved the problem for me:

I noticed that in the terminal used for `dropbox start`, dropbox was telling me what to do. It says:

Please run "echo fs.inotify.max_user_watches=100000 | sudo tee -a /etc/sysctl.conf; sudo sysctl -p" and restart Dropbox to fix the problem.

So I did that, and it fixed the problem for me.

[boxdropping]

It appears the question from dropboxd asking for the root password is related to PolicyKit and the 'pkexec' command, wanting to execute as another user. I am not sure what it is attempting to do under another user, perhaps change ownership as Dropbox on OS X will ask from time to time to obtain root in order to change directory permissions. Regardless it doesn't attempt to su or sudo to another user when PolicyKit is not installed.

PolicyKit is installed with things like libvirt, XFree86 / Linux desktop stuff, and some other things I believe. It got installed when I installed virt-manager so I could run some virtual machines on my Linux server w/ qemu via a X GUI w/ X11 forwarding. I no longer had a need for this, removed PolicyKit (and thus pkexec) and it is no longer asking for root.

If you wish to keep PolicyKit installed, I would suggest finding out how to add privileges for your dropbox user to use pkexec. I was denied after entering the root password as PK was apparently not configured to allow my user, 'dropboxuser', to execute anything with it. I don't think it's harmful; it's probably just trying to change some permissions. But I cannot be sure. You could enable auditing or do some strace/ltrace of the software and determine for sure.

Regards!