4.5.2 The filesystem concept in Debian

Following the Unix tradition, the Debian system provides the filesystem under which physical data on harddisks and other storage devices, and the interaction with the hardware devices such as console screens and remote serial consoles are represented in an unified manner.

Each file, directory, named pipe, or physical device on a Debian system has a data structure called an inode which describes its associated attributes such as the user who owns it (owner), the group that it belongs to, the time last accessed, etc. See /usr/include/linux/fs.h for the exact definition of struct inode in the Debian GNU/Linux system.

This unified representation of physical entities is very powerful since this allows us to use the same command for the same kind of operation on many totally different devices.

All your files could be on one disk --- or you could have 20 disks, some of them connected to a different computer elsewhere on the network. You can't tell just by looking at the directory tree, and nearly all commands work just the same way no matter what physical device(s) your files are really on.