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.\" 3. 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 March 22, 2017 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, mount 113.Em only 114those file systems which are marked as 115.Dq Li late . 116.It Fl l 117When used in conjunction with the 118.Fl a 119option, also mount those file systems which are marked as 120.Dq Li late . 121.It Fl n 122For compatibility with some other implementations, this flag is 123currently a no-op. 124.It Fl o 125Options are specified with a 126.Fl o 127flag followed by a comma separated string of options. 128In case of conflicting options being specified, the rightmost option 129takes effect. 130The following options are available: 131.Bl -tag -width indent 132.It Cm acls 133Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the 134.Xr setfacl 1 135and 136.Xr getfacl 1 137commands. 138This flag is mutually exclusive with 139.Cm nfsv4acls 140flag. 141.It Cm async 142All 143.Tn I/O 144to the file system should be done asynchronously. 145This is a 146.Em dangerous 147flag to set, since it does not guarantee that the file system structure 148on the disk will remain consistent. 149For this reason, the 150.Cm async 151flag should be used sparingly, and only when some data recovery 152mechanism is present. 153.It Cm automounted 154This flag indicates that the file system was mounted by 155.Xr automountd 8 . 156Automounted file systems are automatically unmounted by 157.Xr autounmountd 8 . 158.It Cm autoro 159Mount the file system read-write. 160If that fails with an error that suggests that the media could be read-only, 161then automatically try to mount the file system read-only. 162.It Cm current 163When used with the 164.Fl u 165flag, this is the same as specifying the options currently in effect for 166the mounted file system. 167.It Cm force 168The same as 169.Fl f ; 170forces the revocation of write access when trying to downgrade 171a file system mount status from read-write to read-only. 172Also 173forces the R/W mount of an unclean file system (dangerous; use with caution). 174.It Cm fstab 175When used with the 176.Fl u 177flag, this is the same as specifying all the options listed in the 178.Xr fstab 5 179file for the file system. 180.It Cm late 181This file system should be skipped when 182.Nm 183is run with the 184.Fl a 185flag but without the 186.Fl l 187flag. 188.It Cm mountprog Ns = Ns Aq Ar program 189Force 190.Nm 191to use the specified program to mount the file system, instead of calling 192.Xr nmount 2 193directly. 194For example: 195.Bd -literal 196mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt 197.Ed 198.It Cm multilabel 199Enable multi-label Mandatory Access Control, or MAC, on the specified file 200system. 201If the file system supports multilabel operation, individual labels will 202be maintained for each object in the file system, rather than using a 203single label for all objects. 204An alternative to the 205.Fl l 206flag in 207.Xr tunefs 8 . 208See 209.Xr mac 4 210for more information, which cause the multilabel mount flag to be set 211automatically at mount-time. 212.It Cm nfsv4acls 213Enable NFSv4 ACLs, which can be customized via the 214.Xr setfacl 1 215and 216.Xr getfacl 1 217commands. 218This flag is mutually exclusive with 219.Cm acls 220flag. 221.It Cm noasync 222Metadata I/O should be done synchronously, while data I/O should be done 223asynchronously. 224This is the default. 225.It Cm noatime 226Do not update the file access time when reading from a file. 227This option 228is useful on file systems where there are large numbers of files and 229performance is more critical than updating the file access time (which is 230rarely ever important). 231This option is currently only supported on local file systems. 232.It Cm noauto 233This file system should be skipped when 234.Nm 235is run with the 236.Fl a 237flag. 238.It Cm noclusterr 239Disable read clustering. 240.It Cm noclusterw 241Disable write clustering. 242.It Cm noexec 243Do not allow execution of any binaries on the mounted file system. 244This option is useful for a server that has file systems containing 245binaries for architectures other than its own. 246Note: This option was not designed as a security feature and no 247guarantee is made that it will prevent malicious code execution; for 248example, it is still possible to execute scripts which reside on a 249.Cm noexec 250mounted partition. 251.It Cm nosuid 252Do not allow set-user-identifier or set-group-identifier bits to take effect. 253Note: this option is worthless if a public available suid or sgid 254wrapper like 255.Xr suidperl 1 256is installed on your system. 257It is set automatically when the user does not have super-user privileges. 258.It Cm nosymfollow 259Do not follow symlinks 260on the mounted file system. 261.It Cm ro 262The same as 263.Fl r ; 264mount the file system read-only (even the super-user may not write it). 265.It Cm snapshot 266This option allows a snapshot of the specified file system to be taken. 267The 268.Fl u 269flag is required with this option. 270Note that snapshot files must be created in the file system that is being 271snapshotted. 272You may create up to 20 snapshots per file system. 273Active snapshots are recorded in the superblock, so they persist across unmount 274and remount operations and across system reboots. 275When you are done with a snapshot, it can be removed with the 276.Xr rm 1 277command. 278Snapshots may be removed in any order, however you may not get back all the 279space contained in the snapshot as another snapshot may claim some of the blocks 280that it is releasing. 281Note that the schg flag is set on snapshots to ensure that not even the root 282user can write to them. 283The unlink command makes an exception for snapshot files in that it allows them 284to be removed even though they have the schg flag set, so it is not necessary to 285clear the schg flag before removing a snapshot file. 286.Pp 287Once you have taken a snapshot, there are three interesting things that you can 288do with it: 289.Pp 290.Bl -enum -compact 291.It 292Run 293.Xr fsck 8 294on the snapshot file. 295Assuming that the file system was clean when it was mounted, you should always 296get a clean (and unchanging) result from running fsck on the snapshot. 297This is essentially what the background fsck process does. 298.Pp 299.It 300Run 301.Xr dump 8 302on the snapshot. 303You will get a dump that is consistent with the file system as of the timestamp 304of the snapshot. 305.Pp 306.It 307Mount the snapshot as a frozen image of the file system. 308To mount the snapshot 309.Pa /var/snapshot/snap1 : 310.Bd -literal 311mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 312mount -r /dev/md4 /mnt 313.Ed 314.Pp 315You can now cruise around your frozen 316.Pa /var 317file system at 318.Pa /mnt . 319Everything will be in the same state that it was at the time the snapshot was 320taken. 321The one exception is that any earlier snapshots will appear as zero length 322files. 323When you are done with the mounted snapshot: 324.Bd -literal 325umount /mnt 326mdconfig -d -u 4 327.Ed 328.El 329.It Cm suiddir 330A directory on the mounted file system will respond to the SUID bit 331being set, by setting the owner of any new files to be the same 332as the owner of the directory. 333New directories will inherit the bit from their parents. 334Execute bits are removed from 335the file, and it will not be given to root. 336.Pp 337This feature is designed for use on fileservers serving PC users via 338ftp, SAMBA, or netatalk. 339It provides security holes for shell users and as 340such should not be used on shell machines, especially on home directories. 341This option requires the SUIDDIR 342option in the kernel to work. 343Only UFS file systems support this option. 344See 345.Xr chmod 2 346for more information. 347.It Cm sync 348All 349.Tn I/O 350to the file system should be done synchronously. 351.It Cm update 352The same as 353.Fl u ; 354indicate that the status of an already mounted file system should be changed. 355.It Cm union 356Causes the namespace at the mount point to appear as the union 357of the mounted file system root and the existing directory. 358Lookups will be done in the mounted file system first. 359If those operations fail due to a non-existent file the underlying 360directory is then accessed. 361All creates are done in the mounted file system. 362.El 363.Pp 364Any additional options specific to a file system type that is not 365one of the internally known types (see the 366.Fl t 367option) may be passed as a comma separated list; these options are 368distinguished by a leading 369.Dq \&- 370(dash). 371For example, the 372.Nm 373command: 374.Bd -literal -offset indent 375mount -t cd9660 -o -e /dev/cd0 /cdrom 376.Ed 377.Pp 378causes 379.Nm 380to execute the equivalent of: 381.Bd -literal -offset indent 382/sbin/mount_cd9660 -e /dev/cd0 /cdrom 383.Ed 384.Pp 385Options that take a value are specified using the -option=value syntax: 386.Bd -literal -offset indent 387mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 388.Ed 389.Pp 390is equivalent to 391.Bd -literal -offset indent 392/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 393.Ed 394.Pp 395Additional options specific to file system types 396which are not internally known 397(see the description of the 398.Fl t 399option below) 400may be described in the manual pages for the associated 401.Pa /sbin/mount_ Ns Sy XXX 402utilities. 403.It Fl p 404Print mount information in 405.Xr fstab 5 406format. 407Implies also the 408.Fl v 409option. 410.It Fl r 411The file system is to be mounted read-only. 412Mount the file system read-only (even the super-user may not write it). 413The same as the 414.Cm ro 415argument to the 416.Fl o 417option. 418.It Fl t Cm ufs | Ar external_type 419The argument following the 420.Fl t 421is used to indicate the file system type. 422The type 423.Cm ufs 424is the default. 425The 426.Fl t 427option can be used 428to indicate that the actions should only be taken on 429file systems of the specified type. 430More than one type may be specified in a comma separated list. 431The list of file system types can be prefixed with 432.Dq Li no 433to specify the file system types for which action should 434.Em not 435be taken. 436For example, the 437.Nm 438command: 439.Bd -literal -offset indent 440mount -a -t nonfs,nullfs 441.Ed 442.Pp 443mounts all file systems except those of type 444.Tn NFS 445and 446.Tn NULLFS . 447.Pp 448The default behavior of 449.Nm 450is to pass the 451.Fl t 452option directly to the 453.Xr nmount 2 454system call in the 455.Li fstype 456option. 457.Pp 458However, for the following file system types: 459.Cm cd9660 , 460.Cm mfs , 461.Cm msdosfs , 462.Cm nfs , 463.Cm nullfs , 464.Cm smbfs , 465.Cm udf , 466and 467.Cm unionfs . 468.Nm 469will not call 470.Xr nmount 2 471directly and will instead attempt to execute a program in 472.Pa /sbin/mount_ Ns Sy XXX 473where 474.Sy XXX 475is replaced by the file system type name. 476For example, nfs file systems are mounted by the program 477.Pa /sbin/mount_nfs . 478.Pp 479Most file systems will be dynamically loaded by the kernel 480if not already present, and if the kernel module is available. 481.It Fl u 482The 483.Fl u 484flag indicates that the status of an already mounted file 485system should be changed. 486Any of the options discussed above (the 487.Fl o 488option) 489may be changed; 490also a file system can be changed from read-only to read-write 491or vice versa. 492An attempt to change from read-write to read-only will fail if any 493files on the file system are currently open for writing unless the 494.Fl f 495flag is also specified. 496The set of options is determined by applying the options specified 497in the argument to 498.Fl o 499and finally applying the 500.Fl r 501or 502.Fl w 503option. 504.It Fl v 505Verbose mode. 506If the 507.Fl v 508is used alone, show all file systems, including those that were mounted with the 509.Dv MNT_IGNORE 510flag and show additional information about each file system (including fsid 511when run by root). 512.It Fl w 513The file system object is to be read and write. 514.El 515.Sh ENVIRONMENT 516.Bl -tag -width ".Ev PATH_FSTAB" 517.It Ev PATH_FSTAB 518If the environment variable 519.Ev PATH_FSTAB 520is set, all operations are performed against the specified file. 521.Ev PATH_FSTAB 522will not be honored if the process environment or memory address space is 523considered 524.Dq tainted . 525(See 526.Xr issetugid 2 527for more information.) 528.El 529.Sh FILES 530.Bl -tag -width /etc/fstab -compact 531.It Pa /etc/fstab 532file system table 533.El 534.Sh DIAGNOSTICS 535Various, most of them are self-explanatory. 536.Pp 537.Dl XXXXX file system is not available 538.Pp 539The kernel does not support the respective file system type. 540Note that 541support for a particular file system might be provided either on a static 542(kernel compile-time), or dynamic basis (loaded as a kernel module by 543.Xr kldload 8 ) . 544.Sh SEE ALSO 545.Xr getfacl 1 , 546.Xr setfacl 1 , 547.Xr nmount 2 , 548.Xr acl 3 , 549.Xr mac 4 , 550.Xr cd9660 5 , 551.Xr devfs 5 , 552.Xr ext2fs 5 , 553.Xr fstab 5 , 554.Xr procfs 5 , 555.Xr tmpfs 5 , 556.Xr automount 8 , 557.Xr fstyp 8 , 558.Xr kldload 8 , 559.Xr mount_cd9660 8 , 560.Xr mount_msdosfs 8 , 561.Xr mount_nfs 8 , 562.Xr mount_nullfs 8 , 563.Xr mount_smbfs 8 , 564.Xr mount_udf 8 , 565.Xr mount_unionfs 8 , 566.Xr umount 8 , 567.Xr zfs 8 , 568.Xr zpool 8 569.Sh HISTORY 570A 571.Nm 572utility appeared in 573.At v1 . 574.Sh CAVEATS 575After a successful 576.Nm , 577the permissions on the original mount point determine if 578.Pa ..\& 579is accessible from the mounted file system. 580The minimum permissions for 581the mount point for traversal across the mount point in both 582directions to be possible for all users is 0111 (execute for all). 583.Pp 584Use of the 585.Nm 586is preferred over the use of the file system specific 587.Pa mount_ Ns Sy XXX 588commands. 589In particular, 590.Xr mountd 8 591gets a 592.Dv SIGHUP 593signal (that causes an update of the export list) 594only when the file system is mounted via 595.Nm . 596.Sh BUGS 597It is possible for a corrupted file system to cause a crash. 598