xref: /freebsd/share/man/man5/fstab.5 (revision c93b6e5fa24ba172ab271432c6692f9cc604e15a)
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28.\"     @(#)fstab.5	8.1 (Berkeley) 6/5/93
29.\" $FreeBSD$
30.\"
31.Dd April 14, 2014
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 device or
64remote file system to be mounted.
65The contents are decoded by the
66.Xr strunvis 3
67function.
68This allows using spaces or tabs in the device name which would be
69interpreted as field separators otherwise.
70.Pp
71The second field,
72.Pq Fa fs_file ,
73describes the mount point for the file system.
74For swap partitions, this field should be specified as
75.Dq none .
76The contents are decoded by the
77.Xr strunvis 3
78function, as above.
79.Pp
80The third field,
81.Pq Fa fs_vfstype ,
82describes the type of the file system.
83The system can support various file system types.
84Only the root, /usr, and /tmp file systems need be statically
85compiled into the kernel;
86everything else will be automatically loaded at mount
87time.
88(Exception: the FFS cannot currently be demand-loaded.)
89Some people still prefer to statically
90compile other file systems as well.
91.Pp
92The fourth field,
93.Pq Fa fs_mntops ,
94describes the mount options associated with the file system.
95It is formatted as a comma separated list of options.
96It contains at least the type of mount (see
97.Fa fs_type
98below) plus any additional options appropriate to the file system type.
99See the options flag
100.Pq Fl o
101in the
102.Xr mount 8
103page and the file system specific page, such as
104.Xr mount_nfs 8 ,
105for additional options that may be specified.
106All options that can be given to the file system specific mount commands
107can be used in
108.Nm
109as well.
110They just need to be formatted a bit differently.
111The arguments of the
112.Fl o
113option can be used without the preceding
114.Fl o
115flag.
116Other options need both the file system specific flag and its argument,
117separated by an equal sign.
118For example, mounting an
119.Xr msdosfs 5
120filesystem, the options
121.Bd -literal -offset indent
122-o sync -o noatime -m 644 -M 755 -u foo -g bar
123.Ed
124.Pp
125should be written as
126.Bd -literal -offset indent
127sync,noatime,-m=644,-M=755,-u=foo,-g=bar
128.Ed
129.Pp
130in the option field of
131.Nm .
132.Pp
133If the options
134.Dq userquota
135and/or
136.Dq groupquota
137are specified,
138the file system is automatically processed by the
139.Xr quotacheck 8
140command, and user and/or group disk quotas are enabled with
141.Xr quotaon 8 .
142By default,
143file system quotas are maintained in files named
144.Pa quota.user
145and
146.Pa quota.group
147which are located at the root of the associated file system.
148These defaults may be overridden by putting an equal sign
149and an alternative absolute pathname following the quota option.
150Thus, if the user quota file for
151.Pa /tmp
152is stored in
153.Pa /var/quotas/tmp.user ,
154this location can be specified as:
155.Bd -literal -offset indent
156userquota=/var/quotas/tmp.user
157.Ed
158.Pp
159If the option
160.Dq failok
161is specified,
162the system will ignore any error which happens during the mount of that filesystem,
163which would otherwise cause the system to drop into single user mode.
164This option is implemented by the
165.Xr mount 8
166command and will not be passed to the kernel.
167.Pp
168If the option
169.Dq noauto
170is specified, the file system will not be automatically
171mounted at system startup.
172Note that, for network file systems
173of third party types
174(i.e., types supported by additional software
175not included in the base system)
176to be automatically mounted at system startup,
177the
178.Va extra_netfs_types
179.Xr rc.conf 5
180variable must be used to extend the
181.Xr rc 8
182startup script's list of network file system types.
183.Pp
184If the option
185.Dq late
186is specified, the file system will be automatically mounted
187at a stage of system startup after remote mount points are mounted.
188For more detail about this option,
189see the
190.Xr mount 8
191manual page.
192.Pp
193The type of the mount is extracted from the
194.Fa fs_mntops
195field and stored separately in the
196.Fa fs_type
197field (it is not deleted from the
198.Fa fs_mntops
199field).
200If
201.Fa fs_type
202is
203.Dq rw
204or
205.Dq ro
206then the file system whose name is given in the
207.Fa fs_file
208field is normally mounted read-write or read-only on the
209specified special file.
210.Pp
211If
212.Fa fs_type
213is
214.Dq sw
215then the special file is made available as a piece of swap
216space by the
217.Xr swapon 8
218command at the end of the system reboot procedure.
219For swap devices, the keyword
220.Dq trimonce
221triggers the delivery of a
222.Dv BIO_DELETE
223command to the device to mark
224all blocks as unused.
225For vnode-backed swap spaces,
226.Dq file
227is supported in the
228.Fa fs_mntops
229field.
230When
231.Fa fs_spec
232is an
233.Xr md 4
234device file
235.Pq Do md Dc or Do md[0-9]* Dc
236and
237.Dq file
238is specified in
239.Fa fs_mntopts ,
240an
241.Xr md 4
242device is created with the specified file used as backing store,
243and then the new device is used as swap space.
244Swap entries on
245.Pa .eli
246devices will cause automatic creation of encrypted devices.
247The
248.Dq ealgo ,
249.Dq aalgo ,
250.Dq keylen ,
251.Dq notrim ,
252and
253.Dq sectorsize
254options may be passed to control those
255.Xr geli 8
256parameters.
257The fields other than
258.Fa fs_spec
259and
260.Fa fs_type
261are unused.
262If
263.Fa fs_type
264is specified as
265.Dq xx
266the entry is ignored.
267This is useful to show disk partitions which are currently unused.
268.Pp
269The fifth field,
270.Pq Fa fs_freq ,
271is used for these file systems by the
272.Xr dump 8
273command to determine which file systems need to be dumped.
274If the fifth field is not present, a value of zero is returned and
275.Nm dump
276will assume that the file system does not need to be dumped.
277If the fifth field is greater than 0, then it specifies the number of days
278between dumps for this file system.
279.Pp
280The sixth field,
281.Pq Fa fs_passno ,
282is used by the
283.Xr fsck 8
284and
285.Xr quotacheck 8
286programs to determine the order in which file system and quota
287checks are done at reboot time.
288The
289.Fa fs_passno
290field can be any value between 0 and
291.Ql INT_MAX Ns -1 .
292.Pp
293The root file system should be specified with a
294.Fa fs_passno
295of 1, and other file systems should have a
296.Fa fs_passno
297of 2 or greater.
298A file system with a
299.Fa fs_passno
300value of 1 is always checked sequentially and be completed before
301another file system is processed, and it will be processed before
302all file systems with a larger
303.Fa fs_passno .
304.Pp
305For any given value of
306.Fa fs_passno ,
307file systems within a drive will be checked sequentially,
308but file systems on different drives will be checked at the
309same time to utilize parallelism available in the hardware.
310Once all file system checks are complete for the current
311.Fa fs_passno ,
312the same process will start over for the next
313.Fa fs_passno .
314.Pp
315If the sixth field is not present or is zero,
316a value of zero is returned and
317.Xr fsck 8
318and
319.Xr quotacheck 8
320will assume that the file system does not need to be checked.
321.Pp
322The
323.Fa fs_passno
324field can be used to implement finer control when
325the system utilities may determine that the file system resides
326on a different physical device, when it actually does not, as with a
327.Xr ccd 4
328device.
329All file systems with a lower
330.Fa fs_passno
331value will be completed before starting on file systems with a
332higher
333.Fa fs_passno
334value.
335E.g. all file systems with a
336.Fa fs_passno
337of 2 will be completed before any file systems with a
338.Fa fs_passno
339of 3 or greater are started.
340Gaps are allowed between the different
341.Fa fs_passno
342values.
343E.g. file systems listed in
344.Pa /etc/fstab
345may have
346.Fa fs_passno
347values such as 0, 1, 2, 15, 100, 200, 300, and may appear in any order
348within
349.Pa /etc/fstab .
350.Bd -literal
351#define	FSTAB_RW	"rw"	/* read/write device */
352#define	FSTAB_RQ	"rq"	/* read/write with quotas */
353#define	FSTAB_RO	"ro"	/* read-only device */
354#define	FSTAB_SW	"sw"	/* swap device */
355#define	FSTAB_XX	"xx"	/* ignore totally */
356
357struct fstab {
358	char	*fs_spec;	/* block special device name */
359	char	*fs_file;	/* file system path prefix */
360	char	*fs_vfstype;	/* File system type, ufs, nfs */
361	char	*fs_mntops;	/* Mount options ala -o */
362	char	*fs_type;	/* FSTAB_* from fs_mntops */
363	int	fs_freq;	/* dump frequency, in days */
364	int	fs_passno;	/* pass number on parallel fsck */
365};
366.Ed
367.Pp
368The proper way to read records from
369.Pa fstab
370is to use the routines
371.Xr getfsent 3 ,
372.Xr getfsspec 3 ,
373.Xr getfstype 3 ,
374and
375.Xr getfsfile 3 .
376.Sh FILES
377.Bl -tag -width /etc/fstab -compact
378.It Pa /etc/fstab
379The file
380.Nm
381resides in
382.Pa /etc .
383.El
384.Sh EXAMPLES
385.Bd -literal
386# Device	Mountpoint	FStype	Options		Dump	Pass#
387#
388# UFS file system.
389/dev/da0p2	/		ufs	rw		1	1
390#
391# Swap space on a block device.
392/dev/da0p1	none		swap	sw		0	0
393#
394# Swap space using a block device with GBDE/GELI encyption.
395# aalgo, ealgo, keylen, sectorsize options are available
396# for .eli devices.
397/dev/da1p1.bde	none		swap	sw		0	0
398/dev/da1p2.eli	none		swap	sw		0	0
399#
400# tmpfs.
401tmpfs		/tmp		tmpfs	rw,size=1g,mode=1777	0 0
402#
403# UFS file system on a swap-backed md(4).  /dev/md10 is
404# automatically created.  If it is "md", a unit number
405# will be automatically selected.
406md10		/scratch	mfs	rw,-s1g		0	0
407#
408# Swap space on a vnode-backed md(4).
409md11		none		swap	sw,file=/swapfile	0 0
410#
411# CDROM.  "noauto" option is typically used because the
412# media is removable.
413/dev/cd0	/cdrom		cd9660	ro,noauto	0	0
414#
415# NFS-exported file system.  "serv" is an NFS server name
416# or IP address.
417serv:/export	/nfs		nfs	rw,noinet6	0	0
418.Ed
419.Sh SEE ALSO
420.Xr getfsent 3 ,
421.Xr getvfsbyname 3 ,
422.Xr strunvis 3 ,
423.Xr ccd 4 ,
424.Xr dump 8 ,
425.Xr fsck 8 ,
426.Xr geli 8 ,
427.Xr mount 8 ,
428.Xr quotacheck 8 ,
429.Xr quotaon 8 ,
430.Xr swapon 8 ,
431.Xr umount 8
432.Sh HISTORY
433The
434.Nm
435file format appeared in
436.Bx 4.0 .
437