filesystem(7) DEVICES AND MODULES 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 sys-
tems 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 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 direc-
tories:
/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.
1
filesystem(7) DEVICES AND MODULES filesystem(7)
/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 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 comple-
ment 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(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-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 architecture may
share a single /usr file system. A single
/usr/share file system can be shared by machines
2
filesystem(7) DEVICES AND MODULES filesystem(7)
of any architecture. A machine acting as a file
server may export many different /usr file systems
to support several different 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 administra-
tion.
/usr/games Game binaries and data.
/usr/include Include header files (for C pro-
grams, etc).
/usr/lib Program libraries, various
architecture-dependent databases,
and executables not invoked
directly by the user (system dae-
mons, etc).
/usr/share Subtree for architecture-
independent sharable files.
/usr/share/man Subdirectories for on-line refer-
ence 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:
3
filesystem(7) DEVICES AND MODULES filesystem(7)
/export The default root of the exported
file system tree.
/export/exec/architecture-name
The exported /usr file system sup-
porting architecture-name for the
current release.
/export/exec/architecture-name.release-name
The exported /usr file system sup-
porting architecture-name for Sys-
tem 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 System V
release-name.
/export/root/hostname The exported root file system for
hostname.
/export/swap/hostname The exported swap file for host-
name.
/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).
4