xref: /dragonfly/share/man/man5/fstab.5 (revision a4da4a90) 
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28.\"     @(#)fstab.5	8.1 (Berkeley) 6/5/93
29.\" $FreeBSD: src/share/man/man5/fstab.5,v 1.11.2.8 2003/02/10 12:21:08 des Exp $
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31.Dd March 20, 2020
32.Dt FSTAB 5
33.Os
34.Sh NAME
35.Nm fstab
36.Nd static information about the file systems
37.Sh SYNOPSIS
38.In fstab.h
39.Sh DESCRIPTION
40The file
41.Nm
42contains descriptive information about the various file
43systems.
44.Nm
45is only read by programs, and not written;
46it is the duty of the system administrator to properly create
47and maintain this file.
48Each file system is described on a separate line;
49fields on each line are separated by tabs or spaces.
50The order of records in
51.Nm
52is important because
53.Xr fsck 8 ,
54.Xr mount 8 ,
55and
56.Xr umount 8
57sequentially iterate through
58.Nm
59doing their thing.
60.Pp
61The first field,
62.Pq Fa fs_spec ,
63describes the special file or
64remote file system to be mounted.
65This may be a
66.Pa /dev/<path> ,
67a label from a
68.Xr devtab 5
69(typically
70.Pa /etc/devtab ) ,
71or a
72.Pa <host>:<path>
73for NFS.
74Note that
75.Xr devtab 5
76labels maybe augmented with a
77.Pa .suffix
78trailer.
79For example
80.Pa mydisk.s1a .
81Also note
82.Pa /dev
83based paths can mount serial numbers similar to
84.Xr devtab 5
85labels by using the path
86.Pa /dev/serno/SERIALNO[.suffix] .
87.Pp
88The second field,
89.Pq Fa fs_file ,
90describes the mount point for the file system.
91For swap partitions, this field should be specified as
92.Dq none .
93.Pp
94The third field,
95.Pq Fa fs_vfstype ,
96describes the type of the file system.
97The system can support various file system types.
98Only the root,
99.Pa /usr ,
100and
101.Pa /tmp
102file systems need be statically
103compiled into the kernel;
104everything else will be automatically loaded at mount
105time.
106(Exception: the UFS family - FFS, MFS, and LFS cannot
107currently be demand-loaded.)  Some people still prefer to statically
108compile other file systems as well.
109.Pp
110The most common file system types are:
111.Bl -tag -width ".Em HAMMER2" -offset indent
112.It Em HAMMER
113a local
114.Xr HAMMER 5
115file system
116.It Em HAMMER2
117a local HAMMER2 file system
118.It Em ufs
119a local
120.Xr ffs 5
121.Ux
122file system
123.It Em mfs
124a local memory-based
125.Ux
126file system
127.It Em nfs
128a Sun Microsystems compatible
129.Dq "Network File System"
130.It Em swap
131a disk partition to be used for swapping
132.It Em msdos
133a local
134.Xr msdos 5
135DOS compatible file system
136.It Em cd9660
137a local CD-ROM file system (as per ISO 9660)
138.\" maybe also say Rock Ridge extensions are handled ?
139.It Em procfs
140a file system for accessing process data
141.El
142.Pp
143The fourth field,
144.Pq Fa fs_mntops ,
145describes the mount options associated with the file system.
146It is formatted as a comma separated list of options.
147It contains at least the type of mount (see
148.Fa fs_type
149below) plus any additional options
150appropriate to the file system type.
151See the options flag
152.Pq Fl o
153in the
154.Xr mount 8
155page and the file system specific page, such as
156.Xr mount_nfs 8 ,
157for additional options that may be specified.
158.Pp
159If the options ``userquota'' and/or ``groupquota'' are specified,
160the file system is automatically processed by the
161.Xr quotacheck 8
162command, and user and/or group disk quotas are enabled with
163.Xr quotaon 8 .
164By default,
165file system quotas are maintained in files named
166.Pa quota.user
167and
168.Pa quota.group
169which are located at the root of the associated file system.
170These defaults may be overridden by putting an equal sign
171and an alternative absolute pathname following the quota option.
172Thus, if the user quota file for
173.Pa /tmp
174is stored in
175.Pa /var/quotas/tmp.user ,
176this location can be specified as:
177.Bd -literal -offset indent
178userquota=/var/quotas/tmp.user
179.Ed
180.Pp
181If the option ``noauto'' is specified, the file system will not be automatically
182mounted at system startup.
183This is recommended for all remote file systems other than NFS,
184since only NFS mounts are delayed until after network initialization
185by the
186.Xr rc 8
187startup scripts.
188.Pp
189Swap partitions may specify the option ``crypt'' to automatically encrypt
190the swap partition with a random key.
191Note that you will not be able to
192recover any kernel core dumps if you use this option.
193.Pp
194The type of the mount is extracted from the
195.Fa fs_mntops
196field and stored separately in the
197.Fa fs_type
198field (it is not deleted from the
199.Fa fs_mntops
200field).
201If
202.Fa fs_type
203is ``rw'' or ``ro'' then the file system whose name is given in the
204.Fa fs_file
205field is normally mounted read-write or read-only on the
206specified special file.
207If
208.Fa fs_type
209is ``sw'' then the special file is made available as a piece of swap
210space by the
211.Xr swapon 8
212command at the end of the system reboot procedure.
213The fields other than
214.Fa fs_spec
215and
216.Fa fs_type
217are unused.
218If
219.Fa fs_type
220is specified as ``xx'' the entry is ignored.
221This is useful to show disk partitions which are currently unused.
222.Pp
223The fifth field,
224.Pq Fa fs_freq ,
225is used for these file systems by the
226.Xr dump 8
227command to determine which file systems need to be dumped.
228If the fifth field is not present, a value of zero is returned and
229.Nm dump
230will assume that the file system does not need to be dumped.
231.Pp
232The sixth field,
233.Pq Fa fs_passno ,
234is used by the
235.Xr fsck 8
236program to determine the order in which file system checks are done
237at reboot time.
238The root file system should be specified with a
239.Fa fs_passno
240of 1, and other file systems should have a
241.Fa fs_passno
242of 2.
243File systems within a drive will be checked sequentially,
244but file systems on different drives will be checked at the
245same time to utilize parallelism available in the hardware.
246If the sixth field is not present or is zero,
247a value of zero is returned and
248.Xr fsck 8
249will assume that the file system does not need to be checked.
250.Bd -literal
251#define	FSTAB_RW	"rw"	/* read/write device */
252#define	FSTAB_RQ	"rq"	/* read/write with quotas */
253#define	FSTAB_RO	"ro"	/* read-only device */
254#define	FSTAB_SW	"sw"	/* swap device */
255#define	FSTAB_XX	"xx"	/* ignore totally */
256
257struct fstab {
258	char	*fs_spec;	/* block special device name */
259	char	*fs_file;	/* file system path prefix */
260	char	*fs_vfstype;	/* File system type, ufs, nfs */
261	char	*fs_mntops;	/* Mount options ala -o */
262	char	*fs_type;	/* FSTAB_* from fs_mntops */
263	int	fs_freq;	/* dump frequency, in days */
264	int	fs_passno;	/* pass number on parallel fsck */
265};
266.Ed
267.Pp
268The proper way to read records from
269.Nm
270is to use the routines
271.Xr getfsent 3 ,
272.Xr getfsspec 3 ,
273.Xr getfstype 3 ,
274and
275.Xr getfsfile 3 .
276.Sh FILES
277.Bl -tag -width /etc/fstab -compact
278.It Pa /etc/fstab
279The file
280.Nm
281resides in
282.Pa /etc .
283.El
284.Sh SEE ALSO
285.Xr getfsent 3 ,
286.Xr getvfsbyname 3 ,
287.Xr HAMMER 5 ,
288.\".Xr HAMMER2 5 ,
289.Xr dump 8 ,
290.Xr fsck 8 ,
291.Xr mount 8 ,
292.Xr quotacheck 8 ,
293.Xr quotaon 8 ,
294.Xr swapon 8 ,
295.Xr umount 8
296.Sh HISTORY
297The
298.Nm
299file format appeared in
300.Bx 4.0 .
301