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 November 26, 2004 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 adfpruvw 40.Op Fl F Ar fstab 41.Op Fl o Ar options 42.Op Fl t Ar ufs | 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 Ar ufs | 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 device" 58or 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 noauto , 81excluded by the 82.Fl t 83flag (see below), or if they are already mounted (except the 84root file system which is always remounted to preserve 85traditional single user mode behavior). 86.It Fl d 87Causes everything to be done except for the actual system call. 88This option is useful in conjunction with the 89.Fl v 90flag to 91determine what the 92.Nm 93command is trying to do. 94.It Fl F Ar fstab 95Specify the 96.Pa fstab 97file to use. 98.It Fl f 99Forces the revocation of write access when trying to downgrade 100a file system mount status from read-write to read-only. 101Also 102forces the R/W mount of an unclean file system (dangerous; use with 103caution). 104.It Fl o 105Options are specified with a 106.Fl o 107flag followed by a comma separated string of options. 108In case of conflicting options being specified, the rightmost option 109takes effect. 110The following options are available: 111.Bl -tag -width indent 112.It Cm acls 113Enable Access Control Lists, or ACLS, which can be customized via the 114.Xr setfacl 1 115and 116.Xr getfacl 1 117commands. 118.It Cm async 119All 120.Tn I/O 121to the file system should be done asynchronously. 122This is a 123.Em dangerous 124flag to set, 125and should not be used unless you are prepared to recreate the file 126system should your system crash. 127.It Cm current 128When used with the 129.Fl u 130flag, this is the same as specifying the options currently in effect for 131the mounted file system. 132.It Cm force 133The same as 134.Fl f ; 135forces the revocation of write access when trying to downgrade 136a file system mount status from read-write to read-only. 137Also 138forces the R/W mount of an unclean file system (dangerous; use with caution). 139.It Cm fstab 140When used with the 141.Fl u 142flag, this is the same as specifying all the options listed in the 143.Xr fstab 5 144file for the file system. 145.It Cm multilabel 146Enable multi-label Mandatory Access Control, or MAC, on the specified file 147system. 148If the file system supports multilabel operation, individual labels will 149be maintained for each object in the file system, rather than using a 150single label for all objects. 151An alternative to the 152.Fl l 153flag in 154.Xr tunefs 8 . 155See 156.Xr mac 4 157for more information, which cause the multilabel mount flag to be set 158automatically at mount-time. 159.It Cm noasync 160Metadata I/O should be done synchronously, while data I/O should be done 161asynchronously. 162This is the default. 163.It Cm noatime 164Do not update the file access time when reading from a file. 165This option 166is useful on file systems where there are large numbers of files and 167performance is more critical than updating the file access time (which is 168rarely ever important). 169This option is currently only supported on local file systems. 170.It Cm noauto 171This file system should be skipped when 172.Nm 173is run with the 174.Fl a 175flag. 176.It Cm noclusterr 177Disable read clustering. 178.It Cm noclusterw 179Disable write clustering. 180.It Cm noexec 181Do not allow execution of any binaries on the mounted file system. 182This option is useful for a server that has file systems containing 183binaries for architectures other than its own. 184Note: This option was not designed as a security feature and no 185guarantee is made that it will prevent malicious code execution; for 186example, it is still possible to execute scripts which reside on a 187.Cm noexec 188mounted partition. 189.It Cm nosuid 190Do not allow set-user-identifier or set-group-identifier bits to take effect. 191Note: this option is worthless if a public available suid or sgid 192wrapper like 193.Xr suidperl 1 194is installed on your system. 195It is set automatically when the user does not have super-user privileges. 196.It Cm nosymfollow 197Do not follow symlinks 198on the mounted file system. 199.It Cm ro 200The same as 201.Fl r ; 202mount the file system read-only (even the super-user may not write it). 203.It Cm sync 204All 205.Tn I/O 206to the file system should be done synchronously. 207.It Cm snapshot 208This option allows a snapshot of the specified file system to be taken. 209The 210.Fl u 211flag is required with this option. 212Note that snapshot files must be created in the file system that is being 213snapshotted. 214You may create up to 20 snapshots per file system. 215Active snapshots are recorded in the superblock, so they persist across unmount 216and remount operations and across system reboots. 217When you are done with a snapshot, it can be removed with the 218.Xr rm 1 219command. 220Snapshots may be removed in any order, however you may not get back all the 221space contained in the snapshot as another snapshot may claim some of the blocks 222that it is releasing. 223Note that the schg flag is set on snapshots to ensure that not even the root 224user can write to them. 225The unlink command makes an exception for snapshot files in that it allows them 226to be removed even though they have the schg flag set, so it is not necessary to 227clear the schg flag before removing a snapshot file. 228.Pp 229Once you have taken a snapshot, there are three interesting things that you can 230do with it: 231.Pp 232.Bl -enum -compact 233.It 234Run 235.Xr fsck 8 236on the snapshot file. 237Assuming that the file system was clean when it was mounted, you should always 238get a clean (and unchanging) result from running fsck on the snapshot. 239This is essentially what the background fsck process does. 240.Pp 241.It 242Run 243.Xr dump 8 244on the snapshot. 245You will get a dump that is consistent with the file system as of the timestamp 246of the snapshot. 247.Pp 248.It 249Mount the snapshot as a frozen image of the file system. 250To mount the snapshot 251.Pa /var/snapshot/snap1 : 252.Bd -literal 253mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 254mount -r /dev/md4 /mnt 255.Ed 256.Pp 257You can now cruise around your frozen 258.Pa /var 259file system at 260.Pa /mnt . 261Everything will be in the same state that it was at the time the snapshot was 262taken. 263The one exception is that any earlier snapshots will appear as zero length 264files. 265When you are done with the mounted snapshot: 266.Bd -literal 267umount /mnt 268mdconfig -d -u 4 269.Ed 270.Pp 271Further details can be found in the file at 272.Pa /usr/src/sys/ufs/ffs/README.snapshot . 273.El 274.It Cm suiddir 275A directory on the mounted file system will respond to the SUID bit 276being set, by setting the owner of any new files to be the same 277as the owner of the directory. 278New directories will inherit the bit from their parents. 279Execute bits are removed from 280the file, and it will not be given to root. 281.Pp 282This feature is designed for use on fileservers serving PC users via 283ftp, SAMBA, or netatalk. 284It provides security holes for shell users and as 285such should not be used on shell machines, especially on home directories. 286This option requires the SUIDDIR 287option in the kernel to work. 288Only UFS file systems support this option. 289See 290.Xr chmod 2 291for more information. 292.It Cm update 293The same as 294.Fl u ; 295indicate that the status of an already mounted file system should be changed. 296.It Cm union 297Causes the namespace at the mount point to appear as the union 298of the mounted file system root and the existing directory. 299Lookups will be done in the mounted file system first. 300If those operations fail due to a non-existent file the underlying 301directory is then accessed. 302All creates are done in the mounted file system. 303.El 304.Pp 305Any additional options specific to a file system type that is not 306one of the internally known types (see the 307.Fl t 308option) may be passed as a comma separated list; these options are 309distinguished by a leading 310.Dq \&- 311(dash). 312Options that take a value are specified using the syntax -option=value. 313For example, the 314.Nm 315command: 316.Bd -literal -offset indent 317mount -t unionfs -o -b /sys $HOME/sys 318.Ed 319.Pp 320causes 321.Nm 322to execute the equivalent of: 323.Bd -literal -offset indent 324/sbin/mount_unionfs -b /sys $HOME/sys 325.Ed 326.Pp 327Additional options specific to file system types 328which are not internally known 329(see the description of the 330.Fl t 331option below) 332may be described in the manual pages for the associated 333.Pa /sbin/mount_ Ns Sy XXX 334utilities. 335.It Fl p 336Print mount information in 337.Xr fstab 5 338format. 339Implies also the 340.Fl v 341option. 342.It Fl r 343The file system is to be mounted read-only. 344Mount the file system read-only (even the super-user may not write it). 345The same as the 346.Cm ro 347argument to the 348.Fl o 349option. 350.It Fl t Ar ufs | external_type 351The argument following the 352.Fl t 353is used to indicate the file system type. 354The type 355.Ar ufs 356is the default. 357The 358.Fl t 359option can be used 360to indicate that the actions should only be taken on 361file systems of the specified type. 362More than one type may be specified in a comma separated list. 363The list of file system types can be prefixed with 364.Dq no 365to specify the file system types for which action should 366.Em not 367be taken. 368For example, the 369.Nm 370command: 371.Bd -literal -offset indent 372mount -a -t nonfs,nullfs 373.Ed 374.Pp 375mounts all file systems except those of type 376.Tn NFS 377and 378.Tn NULLFS . 379.Pp 380The default behavior of 381.Nm 382is to pass the 383.Fl t 384option directly to the 385.Xr nmount 2 386system call in the 387.Li fstype 388option. 389.Pp 390However, for the following file system types: 391.Ar cd9660 , 392.Ar mfs , 393.Ar msdosfs , 394.Ar nfs , 395.Ar nfs4 , 396.Ar ntfs , 397.Ar nwfs , 398.Ar nullfs , 399.Ar portalfs , 400.Ar smbfs , 401.Ar udf , 402.Ar umapfs , 403and 404.Ar unionfs , 405.Nm 406will not call 407.Xr nmount 2 408directly and will instead attempt to execute a program in 409.Pa /sbin/mount_ Ns Sy XXX 410where 411.Sy XXX 412is replaced by the file system type name. 413For example, nfs file systems are mounted by the program 414.Pa /sbin/mount_nfs . 415.Pp 416Most file systems will be dynamically loaded by the kernel 417if not already present, and if the kernel module is available. 418.It Fl u 419The 420.Fl u 421flag indicates that the status of an already mounted file 422system should be changed. 423Any of the options discussed above (the 424.Fl o 425option) 426may be changed; 427also a file system can be changed from read-only to read-write 428or vice versa. 429An attempt to change from read-write to read-only will fail if any 430files on the file system are currently open for writing unless the 431.Fl f 432flag is also specified. 433The set of options is determined by applying the options specified 434in the argument to 435.Fl o 436and finally applying the 437.Fl r 438or 439.Fl w 440option. 441.It Fl v 442Verbose mode. 443.It Fl w 444The file system object is to be read and write. 445.El 446.Sh ENVIRONMENT 447.Bl -tag -width ".Ev PATH_FSTAB" 448.It Ev PATH_FSTAB 449If the environment variable 450.Ev PATH_FSTAB 451is set, all operations are performed against the specified file. 452.Ev PATH_FSTAB 453will not be honored if the process environment or memory address space is 454considered 455.Dq tainted . 456(See 457.Xr issetugid 2 458for more information.) 459.El 460.Sh FILES 461.Bl -tag -width /etc/fstab -compact 462.It Pa /etc/fstab 463file system table 464.El 465.Sh DIAGNOSTICS 466Various, most of them are self-explanatory. 467.Pp 468.Dl XXXXX file system is not available 469.Pp 470The kernel does not support the respective file system type. 471Note that 472support for a particular file system might be provided either on a static 473(kernel compile-time), or dynamic basis (loaded as a kernel module by 474.Xr kldload 8 ) . 475.Sh SEE ALSO 476.Xr getfacl 1 , 477.Xr setfacl 1 , 478.Xr nmount 2 , 479.Xr acl 3 , 480.Xr mac 4 , 481.Xr fstab 5 , 482.Xr kldload 8 , 483.Xr mount_cd9660 8 , 484.Xr mount_ext2fs 8 , 485.Xr mount_msdosfs 8 , 486.Xr mount_nfs 8 , 487.Xr mount_ntfs 8 , 488.Xr mount_nullfs 8 , 489.Xr mount_nwfs 8 , 490.Xr mount_portalfs 8 , 491.Xr mount_procfs 8 , 492.Xr mount_smbfs 8 , 493.Xr mount_std 8 , 494.Xr mount_udf 8 , 495.Xr mount_umapfs 8 , 496.Xr mount_unionfs 8 , 497.Xr umount 8 498.Sh CAVEATS 499After a successful 500.Nm , 501the permissions on the original mount point determine if 502.Pa ..\& 503is accessible from the mounted file system. 504The minimum permissions for 505the mount point for traversal across the mount point in both 506directions to be possible for all users is 0111 (execute for all). 507.Sh HISTORY 508A 509.Nm 510utility appeared in 511.At v1 . 512.Sh BUGS 513It is possible for a corrupted file system to cause a crash. 514