Symptoms:

after manually copying files to OwnCloud directory (NAS), they’re still not seen in web interface and are not sync’d to nodes.

Solution:

sudo -u www-data php /var/www/owncloud/occ files:scan --all

Output:

sudo -u www-data php /var/www/owncloud/occ files:scan --all

Scanning files for 2 users
Starting scan for user 1 out of 2 (admin)
Starting scan for user 2 out of 2 (user1)

+---------+-------+--------------+
| Folders | Files | Elapsed time |
+---------+-------+--------------+
| 730     | 7894  | 00:10:55     |
+---------+-------+--------------+