The Role of the Root Filesystem
The utility programs on the root establish a primary environment to craft an arrangement of filesystems, introduce special systems functionality via the server processes (daemons), and configure devices for operation. In addition, the root filesystem possesses the utility tools used to fix, or reload if necessary, other filesystems. These tools are often used to fix the root itself if it is not badly damaged. By virtue of its small size and lack of actively modified files, the root usually survives intact when a system crash occurs. This is all the better for us because we need it to run the system and summarily fix all ills. Should it get destroyed, however, we must completely reload it by some means; that's why some systems have "back up" root filesystems--just in case this actually happens. (With 386BSD, we eventually allow for root filesystem recovery and installation of the first root filesystem by means of a floppy root filesystem, which contains the tools to load the entire system over the network, via a serial port, or from a floppy or cartridge tape dump.)
The root filesystem is a small but essential portion of disk storage. It provides enough functionality for the system to expand its resources to use storage other than the root itself, and configure operations based on arrangements mandated by current conditions. The root filesystem is also the starting point for all filename translations and path searches. As a result, a smaller root with fewer files to search through will generally improve file operations performance.
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