Commonly used commands via ssh with Synology NAS.
Synology Cheat Sheet
sudo -i : Login as root synoindex -R video : Reindex video files
User management
There is no passwd command, user synouser command instead.
Create new user 'tuyen' with password '1' and permission to access FTP (0x01), Audio Station (0x04) and Surveillance Station (0x10)
admin@DiskStation:~$ sudo /usr/syno/sbin/synouser --add tuyen 1 "Tuyen Dang" 0 tuyen@company.com 21
Re-index files
Re-index video files to remove deleted videos from being listed in DS Video
admin@DiskStation:~$ synoindex -R video