Could someone please tell me where I can get an explanation of the UNIX filenames and there functions, e.g. /usr, /etc, /var .
/: The Root Directory. Under UNIX-like system there is just one unified directory, with everything beginning at what is called the root directory. The root directory is symbolized by just a forward slash ("/"), with nothing following it. There are many directories hanging off of the root directory. The contents of the root filesystem should be adequate to boot, restore, recover, and/or repair the system.
/bin: contains commands that may be used by both the system administrator and by users, but which are required in single user mode. It may also contain commands which are used indirectly by scripts.
/sbin: Utilities used for system administration and maintenance. (and other root-only commands) are stored in /sbin.
/boot: is for anything which is used before the kernel execs /sbin/init. This includes saved master boot sectors, sector map files, and anything else that is not directly edited by hand.
/dev Where special files are kept. Special files represent input/output (i/o) devices, like a tty (terminal), a disk drive, or a printer. Because Unix treats such devices as files. /dev also contains a script named MAKEDEV which can create devices as needed. It may also contain a MAKEDEV.local for any local-only devices
/etc: System configuration files and directories. (startup scripts configuration files for networking etc..)
/usr: /usr is shareable, read-only data. it mybe shared with other machines with the same architecture and operating system version. and most of the root directory structure is mirrored here.
--- /usr/bin: most user commands
--- /usr/local: local software
--- /usr/dict: Word lists
--- /usr/etc: Site-wide system configuration
--- /usr/include: Directory for standard include files.
--- /usr/lib: Libraries for programming and packages
--- /usr/man: Manual pages
--- /usr/sbin: Non-essential standard system binaries
--- /usr/share: Architecture-independent data
--- /usr/src: Source code
etc...
/lib: Essential shared libraries and kernel modules.
/proc: information about processes. storage and retrieval of process information as well as other kernel and memory information.
/var: material which is necessarily per-machine. Contains variable data files. This includes spool directories and files, administrative and logging data
--- /var/adm: adminstrative materials (System logging and accounting files)
--- /var/log: Contains miscellaneous log files. Most logs should be written to this directory or an appropriate subdirectory.
--- /var/spool: is traditionally used for machine-local data being spooled to or from UNIX subsystems. print jobs are spooled here for delivery to the lineprinter daemon, mail is spooled for delivery to remote systems, and UUCP files are spooled for transmission. In-bound mail and news are spooled here for delivery to users, and at and cron jobs are spooled for delayed execution by the cron daemon.
etc...
/root: is the home directory for the superuser root. It usually contains things that concern system administration that don't belong in public view, and has read priviledges only for the root user and other administration accounts.
/home: home directories for users. Each user has a username and a directory in /home with that username to use as their home directory. They can place any kind of files there, and set up permissions to allow exactly whom they wish to see their data.
/tmp: temporary files (system scratch files all users can write here).
/lost+found: is used for any pieces of files system can't identify when it cleans up the filesystem(fsck). If you lose some data mysteriously, check here.
/mnt: is just such a temporary mount point. Sometimes it has subdirectories for the different types of filesystems which can be mounted there.