filesystem(7) filesystem(7)
NAME
filesystem - file system organization
SYNOPSIS
/
/usr
DESCRIPTION
The Reliant UNIX file system tree is organized for administrative con-
venience. 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 shar-
able files to be stored on one machine but accessed by many machines
using a remote file access mechanism such as 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 sys-
tems. Two file systems, / (the root) and /usr, must be mounted in
order to have a completely functional system. The root file system is
mounted automatically by the kernel at boot time; the /usr file system
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 the
machine's identity. Executable programs are no
longer kept in /etc.
/home Root of a subtree for user directories.
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/mnt Temporary mount point for file systems. This is an
empty directory on which file systems may be tem-
porarily mounted.
/opt Root of a subtree for add-on application packages.
/proc Root of a subtree for the process file system.
/sbin Essential executables used in the booting process
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, variable) 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 packages.
/var/preserve Backup files for vi(1) and ex(1).
/var/spool Subdirectories for files used in printer spooling,
mail delivery, cron(1M), 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-independent sharable files; the rest
of the /usr tree contains architecture-dependent files. By mounting a
common remote file system, a group of machines with a common architec-
ture 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 sup-
port several different architectures and operating system releases.
Clients usually mount /usr read-only so that they do not accidentally
change any shared files. The /usr file system contains the following
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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
databases, 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.
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
Reliant UNIX release-name.
/export/exec/share
The exported common /usr/share directory tree.
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/export/exec/share.release-name
The exported common /usr/share directory tree for Reliant UNIX
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), ksh(1), sh(1), vi(1), init(1M), mknod(1M), mount(1M), fsck(1M),
introsarm4(4).
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