Write a note about Directory structure with examples.

The FreeBSD directory hierarchy is basic to obtaining an overall understanding of the system. The most significant concept to grasp is that of the root directory, "/" and this directory is the first one mounted at boot time and it contains the base system necessary to prepare the operating system for multi-user operation. The root directory as well contains mount points for every other file system that you may want to mount.

A mount point is a directory where an additional file system is able to be grafted onto the root file system. Standard mount points comprise /usr, /var, /tmp, /mnt, and /cdrom. These directories are typically referenced to entries in the file /etc/fstab. /etc/fstab is a table of various file systems and mount points for reference by the system. The majority of the file systems in /etc/fstab are mounted automatically at boot time unless they contain the noauto option.