4.3BSD-UWisc/man/man5/mntent.5

.\" @(#)mntent.5 1.1 85/12/28 SMI;
.TH MNTENT 5 "21 August 1985"
.SH NAME
mntent \- static information about filesystems
.SH SYNOPSIS
.B #include <mntent.h>
.SH DESCRIPTION
.IX  "mntent file"  ""  "\fLmntent\fP \(em file system static information"
.IX  "file system"  "mntent file"  ""  "\fLmntent\fP \(em static information"
.IX  "static file system information mntent"  ""  "static file system information \(em \fLmntent\fP"
The file
.I /etc/fstab
describes the file systems and swapping partitions used by the local machine.
It is created by the system administrator using a text editor
and processed by commands which mount, unmount, check consistency of,
dump and restore file systems, and by the system in providing
swap space.
.LP
It consists of a number of lines of the form:
.IP
fsname dir type opts freq passno
.LP
an example of which would be:
.IP
/dev/xy0a / 4.2 rw,noquota 1 2
.LP
.LP
The entries from this file are accessed using the routines in
.IR getmntent (3),
which returns a structure of the following form:
.IP
.ta \w'#define'u +\w'char\0\0'u +\w'*mnt_fsname;\0\0'u
.nf
struct mntent {
	char	*mnt_fsname;	/* file system name */
	char	*mnt_dir;	/* file system path prefix */
	char	*mnt_type;	/* 4.2, nfs, swap, or ignore */
	char	*mnt_opts;	/* ro, quota, etc. */
	int	mnt_freq;	/* dump frequency, in days */
	int	mnt_passno;	/* pass number on parallel fsck */
};
.fi
.LP
The fields are separated by white space,
and a `#' as the first non-white character indicates a comment.
.LP
The \fImnt_type\fP field determines how the 
.I mnt_fsname,
and 
.I mnt_opts
fields will be interpreted.
Below is a list of the file system types currently supported and
the way each of them interprets these fields.
.LP
.B 4.2
.IP mnt_fsname 12
Must be a block special device.
.IP mnt_opts 12
Valid opts are ro, rw, quota, noquota.
.LP
.B NFS
.IP mnt_fsname 12
The path on the server of the directory to be served.
.IP mnt_opts 12
Valid opts are ro, rw, quota, noquota, hard, soft.
.LP
.B SWAP
.IP mnt_fsname 12
Must be a block special device swap partition.
.IP mnt_opts 12
Ignored.
.LP
If the
.I mnt_type
is specified as ``ignore'' the entry is ignored.
This is useful to show disk partitions which are currently not used.
.LP
The field \fImnt_freq\fP indicates how often each partition should
be dumped by the
.IR dump (8)
command (and triggers that commands \fBw\fP option which tells
which file systems should be dumped).
Most systems set the \fImnt_freq\fP field to 1 indicating that the
file systems are dumped each day.
.LP
The final field \fImnt_passno\fP is used by the disk consistency
check program
.IR fsck (8)
to allow overlapped checking of file systems during a reboot.  All
file systems with \fImnt_passno\fP of 1 are first checked simultaneosly,
then all file systems with \fImnt_passno\fP of 2, and so on.
It is usual to make the \fImnt_passno\fP of the root file system have
the value 1 and then check one file system on each available disk
drive in each subsequent pass to the exhaustion of file system partitions.
.LP
.I /etc/fstab
is only
.I read
by programs, and not written;
it is the duty of the system administrator to properly create 
and maintain this file.
The order of records in
.I /etc/fstab
is important because
.I fsck,
.I mount,
and
.I umount
process the file sequentially; file systems must appear
\fIafter\fP file systems they are mounted within.
.SH FILES
/etc/fstab
.SH SEE ALSO
fsck(8), getmntent(3), mount(8), quotacheck(8), quotaon(8), umount(8)