Synology DSM is a GNU/Linux distro. It runs the exact same stuff as any other distro, including the kernel and all services and the filesystem. The only differences between building your own NAS with a good server distro like Debian ‘stable’ and running a “commercial” Synology box are: 1.

What is the Synology OS?

DiskStation Manager (DSM) is an intuitive web-based operating system for every Synology NAS, designed to help you manage your digital assets across home and office.

What filesystem does Synology use?

Synology NAS recognizes the following formats: Btrfs, ext3, ext4, FAT32, exFAT, HFS, HFS Plus, and NTFS. Any unrecognized external drive will have to be formatted first before being used on the system.