How to make a backup with deja-dup from command line?
Solution 1:
Déjà Dup is a GUI that uses duplicity as the back-end and hence there are only limited command-line options. You can run man deja-dup and see the various options available. For example to start a backup run:
deja-dup --backup
or to restore a file file:
deja-dup --restore file
(Note that these commands just invoke the GUI from terminal)
To get more powerful options from command-line you should consider installing duplicity which is strictly a CLI.