NAME

fstab − static information about filesystems

SYNOPSIS

#include <mntent.h>

DESCRIPTION

The file /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:

fsname dir type opts freq passno
for example:
/dev/xy0a / efs rw,noquota 1 2

The entries from this file are accessed using the routines in getmntent(3), which returns a structure of the following form:

struct mntent {
char*mnt_fsname;/* filesystem name */
char*mnt_dir;/* filesystem path prefix */
char*mnt_type;/* efs, bell, nfs, or ignore */
char*mnt_opts;/* rw, ro, noquota, quota, hard, soft */
intmnt_freq;/* dump frequency, in days */
intmnt_passno;/* pass number on parallel fsck */
};

Fields are separated by white space; a ‘#’ as the first non-white character indicates a comment. 

The mnt_dir fields is the full path name of the directory to be mounted on. 

The mnt_type field determines how the mnt_fsname and 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:

efs mnt_fsname must be a block special device. 

bell mnt_fsname must be a block special device. 

nfs mnt_fsname the path on the server of the directory to be served. 

If the mnt_type is specified as
ignore , then the entry is ignored.  This is useful to show disk partitions not currently used. 

The mnt_opts field contains a list of comma-separated option words.  Some mnt_opts are valid for all filesystem types, while others apply to a specific type only:

mnt_opts valid on all file systems (the default is rw,suid):

rwread/write. 

roread-only. 

suidset-uid execution allowed. 

nosuidset-uid execution not allowed. 

suidand nosuid are not supported. 

raw=paththe filesystem’s raw device interface pathname. 

fsckfsck(1M) invoked with no filesystem arguments should check this filesystem.

nofsckfsck(1M) should not check this filesystem by default.

hideignore this entry during a mount −a command to allow you to define fstab entries for commonly used filesystems you don’t want to automatically mount. 

mnt_opts specific to nfs (NFS) file systems (the defaults are:      fg,retry=1,timeo=7,retrans=4,port=NFS_PORT,hard with defaults for rsize and wsize set by the kernel):

bgif the first attempt fails, retry in the background. 

fgretry in foreground. 

retry=nset number of failure retries to n. 

rsize=nset read buffer size to n bytes. 

wsize=nset write buffer size to n bytes. 

timeo=nset NFS timeout to n tenths of a second. 

retrans=nset number of NFS retransmissions to n. 

port=nset server IP port number to n. 

softreturn error if server doesn’t respond. 

hardretry request until server responds. 

The bg option causes mount to run in the background if the server’s mountd(1M) does not respond. mount attempts each request retry=n times before giving up.  Once the filesystem is mounted, each nfs request made in the kernel waits timeo=n tenths of a second for a response.  If no response arrives, the time-out is multiplied by 2 and the request is retransmitted.  When retrans=n retransmissions have been sent with no reply a soft mounted filesystem returns an error on the request and a hard mounted filesystem retries the request.  The number of bytes in a read or write request can be set with the rsize and wsize options. 

mnt_freq and mnt_passno are not supported. 

FILES

/etc/fstab

SEE ALSO

getmntent(3), fsck(1M), mount(1M). 

Version 2.5  —  April 22, 1987