Dropbox в deb-based дистрибутивы устанавливается как GUI-пакет, но имеет и консольные команды:

#Старт dropbox
$ dropbox start

#Выгрузить dropbox из памяти 
$ dropbox stop

Проблема: после установки dropbox не синхоронизируется, вывод:

alex@alex:~$ dropbox start
Starting Dropbox...dropbox: locating interpreter
dropbox: logging to /tmp/dropbox-antifreeze-f1Vtsk
dropbox: initializing
dropbox: initializing python 3.7.5
dropbox: setting program path '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/dropbox'
dropbox: setting python path '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649:/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/python-packages.zip'
dropbox: python initialized
dropbox: running dropbox
dropbox: setting args
dropbox: applying overrides
dropbox: running main script
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/cryptography.hazmat.bindings._constant_time.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/cryptography.hazmat.bindings._openssl.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/cryptography.hazmat.bindings._padding.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/apex._apex.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/psutil._psutil_linux.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/psutil._psutil_posix.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/tornado.speedups.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/wrapt._wrappers.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/PyQt5.QtWidgets.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/PyQt5.QtCore.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/PyQt5.QtGui.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/PyQt5.QtNetwork.cpython-37m-x86_64-linux-gnu.so'
dropbox: load fq extension '/home/alex/.dropbox-dist/dropbox-lnx.x86_64-105.4.649/PyQt5.QtDBus.cpython-37m-x86_64-linux-gnu.so'
Dropbox isn't running!
Done!
Unable to monitor entire Dropbox folder hierarchy. 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.

После выполнения рекомендуемой команды

echo fs.inotify.max_user_watches=100000 | sudo tee -a /etc/sysctl.conf; sudo sysctl -p

все заработало.