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 April 28, 2011 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 POSIX.1e Access Control Lists, or ACLs, which can be customized via the 124.Xr setfacl 1 125and 126.Xr getfacl 1 127commands. 128This flag is mutually exclusive with 129.Cm nfsv4acls 130flag. 131.It Cm async 132All 133.Tn I/O 134to the file system should be done asynchronously. 135This is a 136.Em dangerous 137flag to set, since it does not guarantee that the file system structure 138on the disk will remain consistent. 139For this reason, the 140.Cm async 141flag should be used sparingly, and only when some data recovery 142mechanism is present. 143.It Cm current 144When used with the 145.Fl u 146flag, this is the same as specifying the options currently in effect for 147the mounted file system. 148.It Cm force 149The same as 150.Fl f ; 151forces the revocation of write access when trying to downgrade 152a file system mount status from read-write to read-only. 153Also 154forces the R/W mount of an unclean file system (dangerous; use with caution). 155.It Cm fstab 156When used with the 157.Fl u 158flag, this is the same as specifying all the options listed in the 159.Xr fstab 5 160file for the file system. 161.It Cm late 162This file system should be skipped when 163.Nm 164is run with the 165.Fl a 166flag but without the 167.Fl l 168flag. 169.It Cm mountprog Ns = Ns Aq Ar program 170Force 171.Nm 172to use the specified program to mount the file system, instead of calling 173.Xr nmount 2 174directly. For example: 175.Bd -literal 176mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt 177.Ed 178.It Cm multilabel 179Enable multi-label Mandatory Access Control, or MAC, on the specified file 180system. 181If the file system supports multilabel operation, individual labels will 182be maintained for each object in the file system, rather than using a 183single label for all objects. 184An alternative to the 185.Fl l 186flag in 187.Xr tunefs 8 . 188See 189.Xr mac 4 190for more information, which cause the multilabel mount flag to be set 191automatically at mount-time. 192.It Cm nfsv4acls 193Enable NFSv4 ACLs, which can be customized via the 194.Xr setfacl 1 195and 196.Xr getfacl 1 197commands. 198This flag is mutually exclusive with 199.Cm acls 200flag. 201.It Cm noasync 202Metadata I/O should be done synchronously, while data I/O should be done 203asynchronously. 204This is the default. 205.It Cm noatime 206Do not update the file access time when reading from a file. 207This option 208is useful on file systems where there are large numbers of files and 209performance is more critical than updating the file access time (which is 210rarely ever important). 211This option is currently only supported on local file systems. 212.It Cm noauto 213This file system should be skipped when 214.Nm 215is run with the 216.Fl a 217flag. 218.It Cm noclusterr 219Disable read clustering. 220.It Cm noclusterw 221Disable write clustering. 222.It Cm noexec 223Do not allow execution of any binaries on the mounted file system. 224This option is useful for a server that has file systems containing 225binaries for architectures other than its own. 226Note: This option was not designed as a security feature and no 227guarantee is made that it will prevent malicious code execution; for 228example, it is still possible to execute scripts which reside on a 229.Cm noexec 230mounted partition. 231.It Cm nosuid 232Do not allow set-user-identifier or set-group-identifier bits to take effect. 233Note: this option is worthless if a public available suid or sgid 234wrapper like 235.Xr suidperl 1 236is installed on your system. 237It is set automatically when the user does not have super-user privileges. 238.It Cm nosymfollow 239Do not follow symlinks 240on the mounted file system. 241.It Cm ro 242The same as 243.Fl r ; 244mount the file system read-only (even the super-user may not write it). 245.It Cm snapshot 246This option allows a snapshot of the specified file system to be taken. 247The 248.Fl u 249flag is required with this option. 250Note that snapshot files must be created in the file system that is being 251snapshotted. 252You may create up to 20 snapshots per file system. 253Active snapshots are recorded in the superblock, so they persist across unmount 254and remount operations and across system reboots. 255When you are done with a snapshot, it can be removed with the 256.Xr rm 1 257command. 258Snapshots may be removed in any order, however you may not get back all the 259space contained in the snapshot as another snapshot may claim some of the blocks 260that it is releasing. 261Note that the schg flag is set on snapshots to ensure that not even the root 262user can write to them. 263The unlink command makes an exception for snapshot files in that it allows them 264to be removed even though they have the schg flag set, so it is not necessary to 265clear the schg flag before removing a snapshot file. 266.Pp 267Once you have taken a snapshot, there are three interesting things that you can 268do with it: 269.Pp 270.Bl -enum -compact 271.It 272Run 273.Xr fsck 8 274on the snapshot file. 275Assuming that the file system was clean when it was mounted, you should always 276get a clean (and unchanging) result from running fsck on the snapshot. 277This is essentially what the background fsck process does. 278.Pp 279.It 280Run 281.Xr dump 8 282on the snapshot. 283You will get a dump that is consistent with the file system as of the timestamp 284of the snapshot. 285.Pp 286.It 287Mount the snapshot as a frozen image of the file system. 288To mount the snapshot 289.Pa /var/snapshot/snap1 : 290.Bd -literal 291mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 292mount -r /dev/md4 /mnt 293.Ed 294.Pp 295You can now cruise around your frozen 296.Pa /var 297file system at 298.Pa /mnt . 299Everything will be in the same state that it was at the time the snapshot was 300taken. 301The one exception is that any earlier snapshots will appear as zero length 302files. 303When you are done with the mounted snapshot: 304.Bd -literal 305umount /mnt 306mdconfig -d -u 4 307.Ed 308.El 309.It Cm suiddir 310A directory on the mounted file system will respond to the SUID bit 311being set, by setting the owner of any new files to be the same 312as the owner of the directory. 313New directories will inherit the bit from their parents. 314Execute bits are removed from 315the file, and it will not be given to root. 316.Pp 317This feature is designed for use on fileservers serving PC users via 318ftp, SAMBA, or netatalk. 319It provides security holes for shell users and as 320such should not be used on shell machines, especially on home directories. 321This option requires the SUIDDIR 322option in the kernel to work. 323Only UFS file systems support this option. 324See 325.Xr chmod 2 326for more information. 327.It Cm sync 328All 329.Tn I/O 330to the file system should be done synchronously. 331.It Cm update 332The same as 333.Fl u ; 334indicate that the status of an already mounted file system should be changed. 335.It Cm union 336Causes the namespace at the mount point to appear as the union 337of the mounted file system root and the existing directory. 338Lookups will be done in the mounted file system first. 339If those operations fail due to a non-existent file the underlying 340directory is then accessed. 341All creates are done in the mounted file system. 342.El 343.Pp 344Any additional options specific to a file system type that is not 345one of the internally known types (see the 346.Fl t 347option) may be passed as a comma separated list; these options are 348distinguished by a leading 349.Dq \&- 350(dash). 351Options that take a value are specified using the syntax -option=value. 352For example, the 353.Nm 354command: 355.Bd -literal -offset indent 356mount -t cd9660 -o -e /dev/cd0 /cdrom 357.Ed 358.Pp 359causes 360.Nm 361to execute the equivalent of: 362.Bd -literal -offset indent 363/sbin/mount_cd9660 -e /dev/cd0 /cdrom 364.Ed 365.Pp 366Additional options specific to file system types 367which are not internally known 368(see the description of the 369.Fl t 370option below) 371may be described in the manual pages for the associated 372.Pa /sbin/mount_ Ns Sy XXX 373utilities. 374.It Fl p 375Print mount information in 376.Xr fstab 5 377format. 378Implies also the 379.Fl v 380option. 381.It Fl r 382The file system is to be mounted read-only. 383Mount the file system read-only (even the super-user may not write it). 384The same as the 385.Cm ro 386argument to the 387.Fl o 388option. 389.It Fl t Cm ufs | Ar external_type 390The argument following the 391.Fl t 392is used to indicate the file system type. 393The type 394.Cm ufs 395is the default. 396The 397.Fl t 398option can be used 399to indicate that the actions should only be taken on 400file systems of the specified type. 401More than one type may be specified in a comma separated list. 402The list of file system types can be prefixed with 403.Dq Li no 404to specify the file system types for which action should 405.Em not 406be taken. 407For example, the 408.Nm 409command: 410.Bd -literal -offset indent 411mount -a -t nonfs,nullfs 412.Ed 413.Pp 414mounts all file systems except those of type 415.Tn NFS 416and 417.Tn NULLFS . 418.Pp 419The default behavior of 420.Nm 421is to pass the 422.Fl t 423option directly to the 424.Xr nmount 2 425system call in the 426.Li fstype 427option. 428.Pp 429However, for the following file system types: 430.Cm cd9660 , 431.Cm mfs , 432.Cm msdosfs , 433.Cm nfs , 434.Cm ntfs , 435.Cm nwfs , 436.Cm nullfs , 437.Cm oldnfs , 438.Cm portalfs , 439.Cm smbfs , 440.Cm udf , 441and 442.Cm unionfs , 443.Nm 444will not call 445.Xr nmount 2 446directly and will instead attempt to execute a program in 447.Pa /sbin/mount_ Ns Sy XXX 448where 449.Sy XXX 450is replaced by the file system type name. 451For example, nfs file systems are mounted by the program 452.Pa /sbin/mount_nfs . 453.Pp 454Most file systems will be dynamically loaded by the kernel 455if not already present, and if the kernel module is available. 456.It Fl u 457The 458.Fl u 459flag indicates that the status of an already mounted file 460system should be changed. 461Any of the options discussed above (the 462.Fl o 463option) 464may be changed; 465also a file system can be changed from read-only to read-write 466or vice versa. 467An attempt to change from read-write to read-only will fail if any 468files on the file system are currently open for writing unless the 469.Fl f 470flag is also specified. 471The set of options is determined by applying the options specified 472in the argument to 473.Fl o 474and finally applying the 475.Fl r 476or 477.Fl w 478option. 479.It Fl v 480Verbose mode. 481If the 482.Fl v 483is used alone, show all file systems, including those that were mounted with the 484.Dv MNT_IGNORE 485flag and show additional information about each file system (including fsid 486when run by root). 487.It Fl w 488The file system object is to be read and write. 489.El 490.Sh ENVIRONMENT 491.Bl -tag -width ".Ev PATH_FSTAB" 492.It Ev PATH_FSTAB 493If the environment variable 494.Ev PATH_FSTAB 495is set, all operations are performed against the specified file. 496.Ev PATH_FSTAB 497will not be honored if the process environment or memory address space is 498considered 499.Dq tainted . 500(See 501.Xr issetugid 2 502for more information.) 503.El 504.Sh FILES 505.Bl -tag -width /etc/fstab -compact 506.It Pa /etc/fstab 507file system table 508.El 509.Sh DIAGNOSTICS 510Various, most of them are self-explanatory. 511.Pp 512.Dl XXXXX file system is not available 513.Pp 514The kernel does not support the respective file system type. 515Note that 516support for a particular file system might be provided either on a static 517(kernel compile-time), or dynamic basis (loaded as a kernel module by 518.Xr kldload 8 ) . 519.Sh SEE ALSO 520.Xr getfacl 1 , 521.Xr setfacl 1 , 522.Xr nmount 2 , 523.Xr acl 3 , 524.Xr mac 4 , 525.Xr devfs 5 , 526.Xr ext2fs 5 , 527.Xr fstab 5 , 528.Xr procfs 5 , 529.Xr kldload 8 , 530.Xr mount_cd9660 8 , 531.Xr mount_msdosfs 8 , 532.Xr mount_nfs 8 , 533.Xr mount_ntfs 8 , 534.Xr mount_nullfs 8 , 535.Xr mount_nwfs 8 , 536.Xr mount_portalfs 8 , 537.Xr mount_smbfs 8 , 538.Xr mount_udf 8 , 539.Xr mount_unionfs 8 , 540.Xr umount 8 , 541.Xr zfs 8 , 542.Xr zpool 8 543.Sh HISTORY 544A 545.Nm 546utility appeared in 547.At v1 . 548.Sh CAVEATS 549After a successful 550.Nm , 551the permissions on the original mount point determine if 552.Pa ..\& 553is accessible from the mounted file system. 554The minimum permissions for 555the mount point for traversal across the mount point in both 556directions to be possible for all users is 0111 (execute for all). 557.Pp 558Use of the 559.Nm 560is preferred over the use of the file system specific 561.Pa mount_ Ns Sy XXX 562commands. 563In particular, 564.Xr mountd 8 565gets a 566.Dv SIGHUP 567signal (that causes an update of the export list) 568only when the file system is mounted via 569.Nm . 570.Sh BUGS 571It is possible for a corrupted file system to cause a crash. 572