FILESYSTEM(7) RISC/os Reference Manual FILESYSTEM(7)
NAME
filesystem - file system organization
SYNOPSIS
/
/usr
DESCRIPTION
The System V file system tree is organized for administra-
tive convenience. Distinct areas within the file system
tree are provided for files that are private to one machine,
files that can be shared by multiple machines of a common
architecture, files that can be shared by all machines, and
home directories. This organization allows sharable files
to be stored on one machine but accessed by many machines
using a remote file access mechanism such as RFS or NFS.
Grouping together similar files makes the file system tree
easier to upgrade and manage.
The file system tree consists of a root file system and a
collection of mountable file systems. The mount(2) program
attaches mountable file systems to the file system tree at
mount points (directory entries) in the root file system or
other previously mounted file systems. Two file systems, /
(the root) and /usr, must be mounted in order to have a com-
pletely functional system. The root file system is mounted
automatically by the kernel at boot time; the /usr file sys-
tem is mounted by the /etc/rc.boot script, which is run as
part of the booting process.
The root file system contains files that are unique to each
machine. It contains the following directories:
/dev Character and block special files. These device
files provide hooks into hardware devices or
operating system facilities. Typically, device
files are built to match the kernel and hardware
configuration of the machine.
/dev/term Terminal devices.
/dev/pts Pseudo-terminal devices.
/dev/xt Devices used by layers.
/dev/sxt Shell layers device files used by shl.
/etc Machine-specific administrative configuration
files and system administration databases. /etc
may be viewed as the home directory of a
machine, the directory that in a sense defines
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the machine's identity. Executable programs are
no longer kept in /etc.
/home Root of a subtree for user directories.
/mnt Temporary mount point for file systems. This is
an empty directory on which file systems may be
temporarily mounted.
/opt Root of a subtree for add-on application pack-
ages.
/proc Root of a subtree for the process file system.
/sbin Essential executables used in the booting pro-
cess and in manual system recovery. The full
complement of utilities is available only after
/usr is mounted,
/tmp Temporary files; initialized to empty during the
boot operation.
/var Root of a subtree for varying files. Varying
files are files that are unique to a machine but
that can grow to an arbitrary (that is, vari-
able) size. An example is a log file.
/var/adm System logging and accounting files.
/var/cron cron's log file.
/var/mail Where users' mail is kept.
/var/opt Top-level directory used by application pack-
ages.
/var/preserve
Backup files for vi(1) and ex(1).
/var/spool Subdirectories for files used in printer spool-
ing, mail delivery, cron(1), at(1), etc.
/var/tmp Transitory files; initialized to empty during
the boot operation.
Because it is desirable to keep the root file system small
and not volatile, on disk-based systems larger file systems
are often mounted on /home, /opt, /usr, and /var.
The file system mounted on /usr contains architecture-
dependent and architecture-independent sharable files. The
subtree rooted at /usr/share contains architecture-
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independent sharable files; the rest of the /usr tree con-
tains architecture-dependent files. By mounting a common
remote file system, a group of machines with a common archi-
tecture may share a single /usr file system. A single
/usr/share file system can be shared by machines of any
architecture. A machine acting as a file server may export
many different /usr file systems to support several dif-
ferent architectures and operating system releases. Clients
usually mount /usr read-only so that they don't accidentally
change any shared files. The /usr file system contains the
following subdirectories:
/usr/bin
Most system utilities.
/usr/sbin
Executables for system administration.
/usr/games
Game binaries and data.
/usr/include
Include header files (for C programs, etc).
/usr/lib
Program libraries, various architecture-dependent data-
bases, and executables not invoked directly by the user
(system daemons, etc).
/usr/share
Subtree for architecture-independent sharable files.
/usr/share/man
Subdirectories for on-line reference manual pages (if
present).
/usr/share/lib
Architecture-independent databases.
/usr/src
Source code for utilities and libraries.
/usr/ucb
Berkeley compatibility package binaries.
/usr/ucbinclude
Berkeley compatibility package header files.
/usr/ucblib
Berkeley compatibility package libraries.
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A machine with disks may export root file systems, swap
files, and /usr file systems to diskless or partially-disked
machines that mount them into the standard file system
hierarchy. The standard directory tree for sharing these
file systems from a server is:
/export
The default root of the exported file system tree.
/export/exec/architecture-name
The exported /usr file system supporting architecture-
name for the current release.
/export/exec/architecture-name.release-name
The exported /usr file system supporting architecture-
name for System V release-name.
/export/exec/share
The exported common /usr/share directory tree.
/export/exec/share.release-name
The exported common /usr/share directory tree for Sys-
tem V release-name.
/export/root/hostname
The exported root file system for hostname.
/export/swap/hostname
The exported swap file for hostname.
/export/var/hostname
The exported /var directory tree for hostname.
SEE ALSO
at(1), sh(1), vi(1), intro(4), init(1M), mknod(1M),
mount(1M), fsck(1M).
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