filesystem(7) DG/UX 4.30 filesystem(7)
NAME
filesystem - file system organization
SYNOPSIS
/
/usr
DESCRIPTION
The DG/UX directory tree is organized to make system
administration via the sysadm(1M) program easier. Distinct
areas within the directory 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 the sharable files to be stored on
one machine, while being 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(1M) 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
fully functional system. The / (root) and usr file systems
are mounted automatically by the kernel at boot time.
The root file system contains files that are unique to each
machine; it can not be shared among machines. The root file
system contains the following directories:
/dev Character and block special files. Device files
provide hooks into hardware devices or operating
system facilities. The kernel builds new device
files in the /dev directory at every boot.
Typically, device files are built to match the
kernel and hardware configuration of the machine.
/etc Various configuration files and system
administration databases that are machine
specific. You can think of /etc as the ``home
directory'' of a machine, defining its
``identity.'' Executable programs are no longer
kept in /etc.
/sbin The minimum executable programs that are needed to
get a system running. /sbin contains only those
programs that are needed in order to mount the
/usr file system: hostname(1), ifconfig(8c),
init(8), mount(8), and sh(1). After /usr is
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filesystem(7) DG/UX 4.30 filesystem(7)
mounted, the full complement of utilities are
available.
/srv A directory tree used by the sysadm(1M) program to
manage various operating system releases and
clients.
/tmp Temporary files that are deleted at reboot time.
/var Files, such as log files, that are unique to a
machine but that can grow to an arbitrary
(``variable'') size.
/var/adm System logging and accounting files.
/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 that are not deleted at reboot
time.
Because it is desirable to keep the root file system small,
larger file systems are often mounted on /var and /tmp.
The file system mounted on /usr contains architecture-
dependent and architecture-independent shareable files. The
subtree rooted at /usr/share contains architecture-
independent shareable 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 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 to prevent their
accidentally modifying any shared files. The /usr file
system contains the following subdirectories:
/usr/admin Contains the files, directories,
tables, menus, and defauts used by
sysadm(1M).
/usr/bin Executable user commands.
/usr/catman Contains the online manual
reference pages.
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filesystem(7) DG/UX 4.30 filesystem(7)
/usr/etc Executable system administration
programs.
/usr/games Executable game programs and data.
/usr/include Include files.
/usr/lib Program libraries and various
architecture-dependent databases.
/usr/opt Contains application packages.
/usr/pub Various data files.
/usr/release Contains media notices, release
notices, and system package names.
/usr/sbin Commands used by a system
administrator.
/usr/sbin/init.d Contains the exectable files for
setting system run levels.
/usr/src Parent directory for source code.
/usr/stand Contains stand-alone utilities and
bootstrap programs.
/usr/ucb Executable programs descended from
the Berkeley Software Distribution.
/usr/share Subtree for architecture-
independent shareable files.
A machine with disks may export root file systems, swap
files and /usr file systems to operating system clients
(with or without disks), which mount these into the standard
file system hierarchy. The standard directory tree for
exporting these file systems is:
/srv The root of the exported directory
tree.
/srv/admin Contains the sysadm databases and
information files.
/srv/release Contains space for each releases's
usr and client roots.
/srv/share Contains release-independent shared
software.
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filesystem(7) DG/UX 4.30 filesystem(7)
/srv/swap Swap space on a one-per-client
basis.
/srv/release/primary Contains symbolic links to the
server's /usr and / files.
/srv/release/primary/root/hostname
The root file system for OS client
hostname.
/srv/release/primary/root/Kernels
Contains the shared kernels for one
or more OS clients. An OS client's
kernel and root directory must
reside in the same file system for
a successful network boot.
Changes from Previous Releases
The file system layout described here is quite a bit
different from the layout employed previous to release 4.10
of the DG/UX system. For compatibility with earlier
releases, symbolic links are provided for various files and
directories linking their previous names to their current
locations. The symbolic links provided include:
/bin -> /usr/bin All programs previously located in
/bin are now in /usr/bin.
/lib -> /usr/lib All files previously located in
/lib are now in /usr/lib.
/usr/adm -> /var/adm The entire /usr/adm directory has
been moved to /var/adm.
/usr/spool -> /var/spool The entire /usr/spool directory has
been moved to /var/spool.
/usr/tmp -> /var/tmp The /usr/tmp directory has been
moved to /var/tmp.
Note: with the new file system organization, the approach to
repairing a broken file system changes. One must mount /usr
before doing an fsck, for example. If the mount point for
/usr has been destroyed, /usr can be mounted temporarily on
/tmp. If the root file system on a stand-alone system is so
badly damaged that none of these mount points exist, or if
/sbin/mount has been corrupted, the only way to repair it
may be to reinstall the root file system.
SEE ALSO
hostname(1), sh(1), intro(4), ifconfig(1M), init(1M),
mount(1M), fsck(1M), sysadm(1M).
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