4.3BSD-UWisc/man/cat5/fstab.5
FSTAB(5) UNIX Programmer's Manual FSTAB(5)
NAME
fstab - static information about filesystems
SYNOPSIS
#include <mntent.h>
DESCRIPTION
The file /_e_t_c/_f_s_t_a_b describes the filesystems and swapping
partitions used by the local machine. The system adminis-
trator can modify it with a text editor. It is read by com-
mands that mount, unmount, dump, restore, and check the con-
sistency of filesystems; also by the system when providing
swap space. The file consists of a number of lines of the
form:
9 _f_s_n_a_m_e _d_i_r _t_y_p_e _o_p_t_s _f_r_e_q _p_a_s_s_n_o
9 for example:
9 /dev/xy0a / 4.2 rw,noquota 1 2
9
The entries from this file are accessed using the routines
in _g_e_t_m_n_t_e_n_t(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; /* 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 */
};
Fields are separated by white space; a `#' as the first
non-white character indicates a comment.
The _m_n_t__d_i_r fields is the full path name of the directory to
be mounted on.
The _m_n_t__t_y_p_e field determines how the _m_n_t__f_s_n_a_m_e and
_m_n_t__o_p_t_s fields will be interpreted. Here is a list of the
filesystem types currently supported, and the way each of
them interprets these fields:
4.2 _m_n_t__f_s_n_a_m_e Must be a block special device.
nfs _m_n_t__f_s_n_a_m_e the path on the server of the direc-
tory to be served.
swap _m_n_t__f_s_n_a_m_e must be a block special device swap
partition.
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FSTAB(5) UNIX Programmer's Manual FSTAB(5)
If the _m_n_t__t_y_p_e is specified as ignore then the entry is
ignored. This is useful to show disk partitions not
currently used.
The _m_n_t__o_p_t_s field contains a list of comma-separated option
words. Some _m_n_t__o_p_t_s are valid for all filesystem types,
while others apply to a specific type only:
9
_m_n_t__o_p_t_s valid on _a_l_l file systems (the default is
rw,suid):
rw read/write.
ro read-only.
suid set-uid execution allowed.
nosuid set-uid execution not allowed.
9
_m_n_t__o_p_t_s specific to 4.2 file systems (the default is
noquota).
quota usage limits enforced.
noquotausage limits not enforced.
9
_m_n_t__o_p_t_s specific to nfs (NFS) file systems (the
defaults are:
9 fg,retry=1,timeo=7,retrans=4,port=NFS_PORT,hard
9 with defaults for _r_s_i_z_e and _w_s_i_z_e set by the kernel):
bg if the first attempt fails, retry in the
background.
fg retry in foreground.
retry=_n set number of failure retries to _n.
rsize=_n set read buffer size to _n bytes.
wsize=_n set write buffer size to _n _b_y_t_e_s.
timeo=_n set NFS timeout to _n tenths of a second.
retrans=_n set number of NFS retransmissions to _n.
port=_n set server IP port number to _n.
soft return error if server doesn't respond.
9
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FSTAB(5) UNIX Programmer's Manual FSTAB(5)
hard retry request until server responds.
The bg option causes _m_o_u_n_t to run in the background if
the server's _m_o_u_n_t_d(8) does not respond. _m_o_u_n_t 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.
The field _m_n_t__f_r_e_q indicates how often each partition should
be dumped by the _d_u_m_p(8) command (and triggers that
command's w option, which determines what filesystems should
be dumped). Most systems set the _m_n_t__f_r_e_q field to 1, indi-
cating that filesystems are dumped each day.
The final field, _m_n_t__p_a_s_s_n_o, is used by the consistency
checking program _f_s_c_k(8) to allow overlapped checking of
filesystems during a reboot. All filesystems with
_m_n_t__p_a_s_s_n_o of 1 are checked first simultaneously, then all
filesystems with _m_n_t__p_a_s_s_n_o of 2, and so on. It is usual to
make the _m_n_t__p_a_s_s_n_o of the root filesystem have the value 1,
and then check one filesystem on each available disk drive
in each subsequent pass, until all filesystem partitions are
checked.
The /_e_t_c/_f_s_t_a_b file is read only by programs and never writ-
ten; the system administrator must maintain it manually.
The order of records in /_e_t_c/_f_s_t_a_b is important because
_f_s_c_k, _m_o_u_n_t, and _u_m_o_u_n_t process the file sequentially;
filesystems must appear _a_f_t_e_r filesystems they are mounted
within.
FILES
/etc/fstab
SEE ALSO
getmntent(3), fsck(8), mount(8), quotacheck(8), quotaon(8)
Printed 12/27/86 23 September 1985 3