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

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.\" @(#)fstab.5 1.1 85/12/28 SMI;
.TH FSTAB 5 "23 September 1985"
.SH NAME
fstab \- static information about filesystems
.SH SYNOPSIS
.B #include <mntent.h>
.\".SH NOTE    
.\"This file is obsolete and exists only for compatability.
.\"New programs should use
.\".IR mntent (5)
.\"instead.     
.\"The routines for accessing
.\".I /etc/fstab
.\"are now in   
.\".IR getmntent (3).
.SH DESCRIPTION
.IX  "fstab file"  ""  "\fLfstab\fP \(em fileystem static information"
.IX  "fileystem static information"  ""  "fileystem static information \(em \fLfstab\fP"
The file
.I /etc/fstab
describes the filesystems and swapping partitions used by the local machine.
The system administrator can modify it with a text editor.
It is read by commands that mount, unmount, dump, restore,
and check the consistency of filesystems;
also by the system when providing swap space.
The file consists of a number of lines of the form:
.nf
.sp .5
	\fIfsname dir type opts freq passno\fR
.sp .5
for example:
.sp .5v
	/dev/xy0a / 4.2 rw,noquota 1 2
.sp .5v
.fi
.LP
The entries from this file are accessed using the routines in
.IR getmntent (3),
which returns a structure of the following form:
.LP
.RS
.ta \w'#define'u +\w'char\0\0'u +\w'*mnt_fsname;\0\0'u
.nf
struct mntent {
	char	*mnt_fsname;	/* filesystem name */
	char	*mnt_dir;	/* filesystem path prefix */
	char	*mnt_type;	/* 4.2, nfs, swap, or ignore */
	char	*mnt_opts;	/* rw, ro, noquota, quota, hard, soft */
	int	mnt_freq;	/* dump frequency, in days */
	int	mnt_passno;	/* pass number on parallel fsck */
};
.fi
.RE
.LP
Fields are separated by white space;
a `#' as the first non-white character indicates a comment.
.LP
The 
.I mnt_dir
fields is the full path name of the directory to be mounted on.
.LP
The
.I mnt_type
field determines how the 
.I mnt_fsname
and 
.I mnt_opts
fields will be interpreted.
Here is a list of the filesystem types currently supported,
and the way each of them interprets these fields:
.ta \w'mnt_fsname\0\0'u
.TP 10
.B 4.2
\fImnt_fsname\fR	Must be a block special device.
.\".br
.\"\fImnt_opts\fR	valid options are:
.\".BI ro , 
.\".BI rw , 
.\".BI quota , 
.\"and
.\".BI noquota .
.TP 10
.B nfs
\fImnt_fsname\fR	the path on the server of the directory to be served.
.\".br
.\"\fImnt_opts\fR	valid options are:
.\".BI ro , 
.\".BI rw , 
.\".BI quota , 
.\".BI noquota , 
.\".BI hard , 
.\"and
.\".BI soft .
.TP 10
.B swap
\fImnt_fsname\fR	must be a block special device swap partition.
.\".br
.\"\fImnt_opts\fR	are ignored.
.LP
If the
.I mnt_type
is specified as
.B ignore
then the entry is ignored.
This is useful to show disk partitions not currently used.
.LP
The 
.I mnt_opts
field contains a list of comma-separated option words.  Some
.I mnt_opts
are valid for all filesystem types, while others apply to a
specific type only:
.sp .5
.IP 
.I mnt_opts
valid on 
.I all 
file systems (the default is
.BR rw,suid ):
.RS
.IP \fBrw\fR .75i
read/write.
.IP \fBro\fR
read-only.
.IP \fBsuid\fR
set-uid execution allowed.
.IP \fBnosuid\fR
set-uid execution not allowed.
.RE
.sp .5
.IP
.I mnt_opts 
specific to
.B 4.2
file systems (the default is
.BR noquota ).
.RS
.IP \fBquota\fR .75i
usage limits enforced.
.IP \fBnoquota\fR
usage limits not enforced.
.RE
.sp .5
.IP
.I mnt_opts
specific to 
.B nfs
(NFS) file systems (the defaults are:
.sp .5
.B \0\0\0\0\0fg,retry=1,timeo=7,retrans=4,port=NFS_PORT,hard\fR
.sp .5
with defaults for 
.I rsize 
and 
.I wsize 
set by the kernel):
.RS
.IP \fBbg\fR 1i
if the first attempt fails, retry in the background.
.IP \fBfg\fR
retry in foreground.
.IP \fBretry=\fIn\fR
set number of failure retries to 
.I n.
.IP \fBrsize=\fIn\fR
set read buffer size to 
.I n 
bytes.
.IP \fBwsize=\fIn\fR
set write buffer size to 
.I 
n bytes.
.IP \fBtimeo=\fIn\fR
set NFS timeout to 
.I n 
tenths of a second.
.IP \fBretrans=\fIn\fR
set number of NFS retransmissions to 
.I n.
.IP \fBport=\fIn\fR
set server IP port number to 
.I n.
.IP \fBsoft\fR
return error if server doesn't respond.
.IP \fBhard\fR
retry request until server responds.
.RE
.IP
The
.B bg
option causes 
.I mount
to run in the background if the server's
.IR mountd (8)
does not respond.  
.I mount 
attempts each request
.BI retry= n
times before giving up.  Once the filesystem is mounted,
each 
.B nfs 
request made in the kernel waits
.BI timeo= n
tenths of a second for a response.  If no response arrives, the
time-out is multiplied by 
.B 2 
and the request is retransmitted.  When
.BI retrans= n
retransmissions have been sent with no reply a
.B soft
mounted filesystem returns an error on the request and a
.B hard
mounted filesystem retries the request.
The number of bytes in a read or write request can be set with the
.B rsize
and
.B wsize
options.
.LP
The field
.I mnt_freq
indicates how often each partition should be dumped by the
.IR dump (8)
command (and triggers that command's
.B w
option, which determines what filesystems should be dumped).
Most systems set the
.I mnt_freq
field to 1, indicating that filesystems are dumped each day.
.LP
The final field,
.IR mnt_passno ,
is used by the consistency checking program
.IR fsck (8)
to allow overlapped checking of filesystems during a reboot.
All filesystems with
.I mnt_passno
of 
.B 1 
are checked first simultaneously, then all filesystems with
.I mnt_passno
of 
.BR 2 , 
and so on.  It is usual to make the
.I mnt_passno
of the root filesystem have the value 
.BR 1 ,
and then check one filesystem on each available disk drive
in each subsequent pass, until all filesystem partitions are checked.
.LP
The
.I /etc/fstab
file is read only by programs and never written;
the system administrator must maintain it manually.
The order of records in
.I /etc/fstab
is important because
.I fsck,
.I mount,
and
.I umount
process the file sequentially;
filesystems must appear 
.I after 
filesystems they are mounted within.
.SH FILES
/etc/fstab
.SH SEE ALSO
getmntent(3), fsck(8), mount(8), quotacheck(8), quotaon(8)