1.\" Copyright (c) 1980, 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mount.8 8.8 (Berkeley) 6/16/94 29.\" $FreeBSD$ 30.\" 31.Dd July 12, 2006 32.Dt MOUNT 8 33.Os 34.Sh NAME 35.Nm mount 36.Nd mount file systems 37.Sh SYNOPSIS 38.Nm 39.Op Fl adflpruvw 40.Op Fl F Ar fstab 41.Op Fl o Ar options 42.Op Fl t Cm ufs | Ar external_type 43.Nm 44.Op Fl dfpruvw 45.Ar special | node 46.Nm 47.Op Fl dfpruvw 48.Op Fl o Ar options 49.Op Fl t Cm ufs | Ar external_type 50.Ar special node 51.Sh DESCRIPTION 52The 53.Nm 54utility calls the 55.Xr nmount 2 56system call to prepare and graft a 57.Ar special 58device or the remote node (rhost:path) on to the file system tree at the point 59.Ar node . 60If either 61.Ar special 62or 63.Ar node 64are not provided, the appropriate information is taken from the 65.Xr fstab 5 66file. 67.Pp 68The system maintains a list of currently mounted file systems. 69If no arguments are given to 70.Nm , 71this list is printed. 72.Pp 73The options are as follows: 74.Bl -tag -width indent 75.It Fl a 76All the file systems described in 77.Xr fstab 5 78are mounted. 79Exceptions are those marked as 80.Dq Li noauto , 81those marked as 82.Dq Li late 83(unless the 84.Fl l 85option was specified), 86those excluded by the 87.Fl t 88flag (see below), or if they are already mounted (except the 89root file system which is always remounted to preserve 90traditional single user mode behavior). 91.It Fl d 92Causes everything to be done except for the actual system call. 93This option is useful in conjunction with the 94.Fl v 95flag to 96determine what the 97.Nm 98command is trying to do. 99.It Fl F Ar fstab 100Specify the 101.Pa fstab 102file to use. 103.It Fl f 104Forces the revocation of write access when trying to downgrade 105a file system mount status from read-write to read-only. 106Also 107forces the R/W mount of an unclean file system (dangerous; use with 108caution). 109.It Fl l 110When used in conjunction with the 111.Fl a 112option, also mount those file systems which are marked as 113.Dq Li late . 114.It Fl o 115Options are specified with a 116.Fl o 117flag followed by a comma separated string of options. 118In case of conflicting options being specified, the rightmost option 119takes effect. 120The following options are available: 121.Bl -tag -width indent 122.It Cm acls 123Enable Access Control Lists, or ACLS, which can be customized via the 124.Xr setfacl 1 125and 126.Xr getfacl 1 127commands. 128.It Cm async 129All 130.Tn I/O 131to the file system should be done asynchronously. 132This is a 133.Em dangerous 134flag to set, since it does not guarantee that the file system structure 135on the disk will remain consistent. 136For this reason, the 137.Cm async 138flag should be used sparingly, and only when some data recovery 139mechanism is present. 140.It Cm current 141When used with the 142.Fl u 143flag, this is the same as specifying the options currently in effect for 144the mounted file system. 145.It Cm force 146The same as 147.Fl f ; 148forces the revocation of write access when trying to downgrade 149a file system mount status from read-write to read-only. 150Also 151forces the R/W mount of an unclean file system (dangerous; use with caution). 152.It Cm fstab 153When used with the 154.Fl u 155flag, this is the same as specifying all the options listed in the 156.Xr fstab 5 157file for the file system. 158.It Cm late 159This file system should be skipped when 160.Nm 161is run with the 162.Fl a 163flag but without the 164.Fl l 165flag. 166.It Cm multilabel 167Enable multi-label Mandatory Access Control, or MAC, on the specified file 168system. 169If the file system supports multilabel operation, individual labels will 170be maintained for each object in the file system, rather than using a 171single label for all objects. 172An alternative to the 173.Fl l 174flag in 175.Xr tunefs 8 . 176See 177.Xr mac 4 178for more information, which cause the multilabel mount flag to be set 179automatically at mount-time. 180.It Cm noasync 181Metadata I/O should be done synchronously, while data I/O should be done 182asynchronously. 183This is the default. 184.It Cm noatime 185Do not update the file access time when reading from a file. 186This option 187is useful on file systems where there are large numbers of files and 188performance is more critical than updating the file access time (which is 189rarely ever important). 190This option is currently only supported on local file systems. 191.It Cm noauto 192This file system should be skipped when 193.Nm 194is run with the 195.Fl a 196flag. 197.It Cm noclusterr 198Disable read clustering. 199.It Cm noclusterw 200Disable write clustering. 201.It Cm noexec 202Do not allow execution of any binaries on the mounted file system. 203This option is useful for a server that has file systems containing 204binaries for architectures other than its own. 205Note: This option was not designed as a security feature and no 206guarantee is made that it will prevent malicious code execution; for 207example, it is still possible to execute scripts which reside on a 208.Cm noexec 209mounted partition. 210.It Cm nosuid 211Do not allow set-user-identifier or set-group-identifier bits to take effect. 212Note: this option is worthless if a public available suid or sgid 213wrapper like 214.Xr suidperl 1 215is installed on your system. 216It is set automatically when the user does not have super-user privileges. 217.It Cm nosymfollow 218Do not follow symlinks 219on the mounted file system. 220.It Cm ro 221The same as 222.Fl r ; 223mount the file system read-only (even the super-user may not write it). 224.It Cm snapshot 225This option allows a snapshot of the specified file system to be taken. 226The 227.Fl u 228flag is required with this option. 229Note that snapshot files must be created in the file system that is being 230snapshotted. 231You may create up to 20 snapshots per file system. 232Active snapshots are recorded in the superblock, so they persist across unmount 233and remount operations and across system reboots. 234When you are done with a snapshot, it can be removed with the 235.Xr rm 1 236command. 237Snapshots may be removed in any order, however you may not get back all the 238space contained in the snapshot as another snapshot may claim some of the blocks 239that it is releasing. 240Note that the schg flag is set on snapshots to ensure that not even the root 241user can write to them. 242The unlink command makes an exception for snapshot files in that it allows them 243to be removed even though they have the schg flag set, so it is not necessary to 244clear the schg flag before removing a snapshot file. 245.Pp 246Once you have taken a snapshot, there are three interesting things that you can 247do with it: 248.Pp 249.Bl -enum -compact 250.It 251Run 252.Xr fsck 8 253on the snapshot file. 254Assuming that the file system was clean when it was mounted, you should always 255get a clean (and unchanging) result from running fsck on the snapshot. 256This is essentially what the background fsck process does. 257.Pp 258.It 259Run 260.Xr dump 8 261on the snapshot. 262You will get a dump that is consistent with the file system as of the timestamp 263of the snapshot. 264.Pp 265.It 266Mount the snapshot as a frozen image of the file system. 267To mount the snapshot 268.Pa /var/snapshot/snap1 : 269.Bd -literal 270mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 271mount -r /dev/md4 /mnt 272.Ed 273.Pp 274You can now cruise around your frozen 275.Pa /var 276file system at 277.Pa /mnt . 278Everything will be in the same state that it was at the time the snapshot was 279taken. 280The one exception is that any earlier snapshots will appear as zero length 281files. 282When you are done with the mounted snapshot: 283.Bd -literal 284umount /mnt 285mdconfig -d -u 4 286.Ed 287.Pp 288Further details can be found in the file at 289.Pa /usr/src/sys/ufs/ffs/README.snapshot . 290.El 291.It Cm suiddir 292A directory on the mounted file system will respond to the SUID bit 293being set, by setting the owner of any new files to be the same 294as the owner of the directory. 295New directories will inherit the bit from their parents. 296Execute bits are removed from 297the file, and it will not be given to root. 298.Pp 299This feature is designed for use on fileservers serving PC users via 300ftp, SAMBA, or netatalk. 301It provides security holes for shell users and as 302such should not be used on shell machines, especially on home directories. 303This option requires the SUIDDIR 304option in the kernel to work. 305Only UFS file systems support this option. 306See 307.Xr chmod 2 308for more information. 309.It Cm sync 310All 311.Tn I/O 312to the file system should be done synchronously. 313.It Cm update 314The same as 315.Fl u ; 316indicate that the status of an already mounted file system should be changed. 317.It Cm union 318Causes the namespace at the mount point to appear as the union 319of the mounted file system root and the existing directory. 320Lookups will be done in the mounted file system first. 321If those operations fail due to a non-existent file the underlying 322directory is then accessed. 323All creates are done in the mounted file system. 324.El 325.Pp 326Any additional options specific to a file system type that is not 327one of the internally known types (see the 328.Fl t 329option) may be passed as a comma separated list; these options are 330distinguished by a leading 331.Dq \&- 332(dash). 333Options that take a value are specified using the syntax -option=value. 334For example, the 335.Nm 336command: 337.Bd -literal -offset indent 338mount -t unionfs -o -b /sys $HOME/sys 339.Ed 340.Pp 341causes 342.Nm 343to execute the equivalent of: 344.Bd -literal -offset indent 345/sbin/mount_unionfs -b /sys $HOME/sys 346.Ed 347.Pp 348Additional options specific to file system types 349which are not internally known 350(see the description of the 351.Fl t 352option below) 353may be described in the manual pages for the associated 354.Pa /sbin/mount_ Ns Sy XXX 355utilities. 356.It Fl p 357Print mount information in 358.Xr fstab 5 359format. 360Implies also the 361.Fl v 362option. 363.It Fl r 364The file system is to be mounted read-only. 365Mount the file system read-only (even the super-user may not write it). 366The same as the 367.Cm ro 368argument to the 369.Fl o 370option. 371.It Fl t Cm ufs | Ar external_type 372The argument following the 373.Fl t 374is used to indicate the file system type. 375The type 376.Cm ufs 377is the default. 378The 379.Fl t 380option can be used 381to indicate that the actions should only be taken on 382file systems of the specified type. 383More than one type may be specified in a comma separated list. 384The list of file system types can be prefixed with 385.Dq Li no 386to specify the file system types for which action should 387.Em not 388be taken. 389For example, the 390.Nm 391command: 392.Bd -literal -offset indent 393mount -a -t nonfs,nullfs 394.Ed 395.Pp 396mounts all file systems except those of type 397.Tn NFS 398and 399.Tn NULLFS . 400.Pp 401The default behavior of 402.Nm 403is to pass the 404.Fl t 405option directly to the 406.Xr nmount 2 407system call in the 408.Li fstype 409option. 410.Pp 411However, for the following file system types: 412.Cm cd9660 , 413.Cm mfs , 414.Cm msdosfs , 415.Cm nfs , 416.Cm nfs4 , 417.Cm ntfs , 418.Cm nwfs , 419.Cm nullfs , 420.Cm portalfs , 421.Cm smbfs , 422.Cm udf , 423and 424.Cm unionfs , 425.Nm 426will not call 427.Xr nmount 2 428directly and will instead attempt to execute a program in 429.Pa /sbin/mount_ Ns Sy XXX 430where 431.Sy XXX 432is replaced by the file system type name. 433For example, nfs file systems are mounted by the program 434.Pa /sbin/mount_nfs . 435.Pp 436Most file systems will be dynamically loaded by the kernel 437if not already present, and if the kernel module is available. 438.It Fl u 439The 440.Fl u 441flag indicates that the status of an already mounted file 442system should be changed. 443Any of the options discussed above (the 444.Fl o 445option) 446may be changed; 447also a file system can be changed from read-only to read-write 448or vice versa. 449An attempt to change from read-write to read-only will fail if any 450files on the file system are currently open for writing unless the 451.Fl f 452flag is also specified. 453The set of options is determined by applying the options specified 454in the argument to 455.Fl o 456and finally applying the 457.Fl r 458or 459.Fl w 460option. 461.It Fl v 462Verbose mode. 463.It Fl w 464The file system object is to be read and write. 465.El 466.Sh ENVIRONMENT 467.Bl -tag -width ".Ev PATH_FSTAB" 468.It Ev PATH_FSTAB 469If the environment variable 470.Ev PATH_FSTAB 471is set, all operations are performed against the specified file. 472.Ev PATH_FSTAB 473will not be honored if the process environment or memory address space is 474considered 475.Dq tainted . 476(See 477.Xr issetugid 2 478for more information.) 479.El 480.Sh FILES 481.Bl -tag -width /etc/fstab -compact 482.It Pa /etc/fstab 483file system table 484.El 485.Sh DIAGNOSTICS 486Various, most of them are self-explanatory. 487.Pp 488.Dl XXXXX file system is not available 489.Pp 490The kernel does not support the respective file system type. 491Note that 492support for a particular file system might be provided either on a static 493(kernel compile-time), or dynamic basis (loaded as a kernel module by 494.Xr kldload 8 ) . 495.Sh SEE ALSO 496.Xr getfacl 1 , 497.Xr setfacl 1 , 498.Xr nmount 2 , 499.Xr acl 3 , 500.Xr mac 4 , 501.Xr ext2fs 5 , 502.Xr fstab 5 , 503.Xr procfs 5 , 504.Xr kldload 8 , 505.Xr mount_cd9660 8 , 506.Xr mount_msdosfs 8 , 507.Xr mount_nfs 8 , 508.Xr mount_ntfs 8 , 509.Xr mount_nullfs 8 , 510.Xr mount_nwfs 8 , 511.Xr mount_portalfs 8 , 512.Xr mount_smbfs 8 , 513.Xr mount_udf 8 , 514.Xr mount_unionfs 8 , 515.Xr umount 8 516.Sh CAVEATS 517After a successful 518.Nm , 519the permissions on the original mount point determine if 520.Pa ..\& 521is accessible from the mounted file system. 522The minimum permissions for 523the mount point for traversal across the mount point in both 524directions to be possible for all users is 0111 (execute for all). 525.Sh HISTORY 526A 527.Nm 528utility appeared in 529.At v1 . 530.Sh BUGS 531It is possible for a corrupted file system to cause a crash. 532