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 Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar 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 Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar 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 I/O to the file system should be done asynchronously. 143This is a 144.Em dangerous 145flag to set, since it does not guarantee that the file system structure 146on the disk will remain consistent. 147For this reason, the 148.Cm async 149flag should be used sparingly, and only when some data recovery 150mechanism is present. 151.It Cm automounted 152This flag indicates that the file system was mounted by 153.Xr automountd 8 . 154Automounted file systems are automatically unmounted by 155.Xr autounmountd 8 . 156.It Cm autoro 157Mount the file system read-write. 158If that fails with an error that suggests that the media could be read-only, 159then automatically try to mount the file system read-only. 160.It Cm current 161When used with the 162.Fl u 163flag, this is the same as specifying the options currently in effect for 164the mounted file system. 165.It Cm force 166The same as 167.Fl f ; 168forces the revocation of write access when trying to downgrade 169a file system mount status from read-write to read-only. 170Also 171forces the R/W mount of an unclean file system (dangerous; use with caution). 172.It Cm fstab 173When used with the 174.Fl u 175flag, this is the same as specifying all the options listed in the 176.Xr fstab 5 177file for the file system. 178.It Cm late 179This file system should be skipped when 180.Nm 181is run with the 182.Fl a 183flag but without the 184.Fl l 185flag. 186.It Cm mountprog Ns = Ns Aq Ar program 187Force 188.Nm 189to use the specified program to mount the file system, instead of calling 190.Xr nmount 2 191directly. 192For example: 193.Bd -literal 194mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt 195.Ed 196.It Cm multilabel 197Enable multi-label Mandatory Access Control, or MAC, on the specified file 198system. 199If the file system supports multilabel operation, individual labels will 200be maintained for each object in the file system, rather than using a 201single label for all objects. 202An alternative to the 203.Fl l 204flag in 205.Xr tunefs 8 . 206See 207.Xr mac 4 208for more information, which cause the multilabel mount flag to be set 209automatically at mount-time. 210.It Cm nfsv4acls 211Enable NFSv4 ACLs, which can be customized via the 212.Xr setfacl 1 213and 214.Xr getfacl 1 215commands. 216This flag is mutually exclusive with 217.Cm acls 218flag. 219.It Cm noasync 220Metadata I/O should be done synchronously, while data I/O should be done 221asynchronously. 222This is the default. 223.It Cm noatime 224Do not update the file access time when reading from a file. 225This option 226is useful on file systems where there are large numbers of files and 227performance is more critical than updating the file access time (which is 228rarely ever important). 229This option is currently only supported on local file systems. 230.It Cm noauto 231This file system should be skipped when 232.Nm 233is run with the 234.Fl a 235flag. 236.It Cm noclusterr 237Disable read clustering. 238.It Cm noclusterw 239Disable write clustering. 240.It Cm noexec 241Do not allow execution of any binaries on the mounted file system. 242This option is useful for a server that has file systems containing 243binaries for architectures other than its own. 244Note: This option was not designed as a security feature and no 245guarantee is made that it will prevent malicious code execution; for 246example, it is still possible to execute scripts which reside on a 247.Cm noexec 248mounted partition. 249.It Cm nosuid 250Do not allow set-user-identifier or set-group-identifier bits to take effect. 251Note: this option is worthless if a public available suid or sgid 252wrapper like 253.Xr suidperl 1 254is installed on your system. 255It is set automatically when the user does not have super-user privileges. 256.It Cm nosymfollow 257Do not follow symlinks 258on the mounted file system. 259.It Cm ro 260The same as 261.Fl r ; 262mount the file system read-only (even the super-user may not write it). 263.It Cm snapshot 264This option allows a snapshot of the specified file system to be taken. 265The 266.Fl u 267flag is required with this option. 268Note that snapshot files must be created in the file system that is being 269snapshotted. 270You may create up to 20 snapshots per file system. 271Active snapshots are recorded in the superblock, so they persist across unmount 272and remount operations and across system reboots. 273When you are done with a snapshot, it can be removed with the 274.Xr rm 1 275command. 276Snapshots may be removed in any order, however you may not get back all the 277space contained in the snapshot as another snapshot may claim some of the blocks 278that it is releasing. 279Note that the schg flag is set on snapshots to ensure that not even the root 280user can write to them. 281The unlink command makes an exception for snapshot files in that it allows them 282to be removed even though they have the schg flag set, so it is not necessary to 283clear the schg flag before removing a snapshot file. 284.Pp 285Once you have taken a snapshot, there are three interesting things that you can 286do with it: 287.Pp 288.Bl -enum -compact 289.It 290Run 291.Xr fsck 8 292on the snapshot file. 293Assuming that the file system was clean when it was mounted, you should always 294get a clean (and unchanging) result from running fsck on the snapshot. 295This is essentially what the background fsck process does. 296.Pp 297.It 298Run 299.Xr dump 8 300on the snapshot. 301You will get a dump that is consistent with the file system as of the timestamp 302of the snapshot. 303.Pp 304.It 305Mount the snapshot as a frozen image of the file system. 306To mount the snapshot 307.Pa /var/snapshot/snap1 : 308.Bd -literal 309mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 310mount -r /dev/md4 /mnt 311.Ed 312.Pp 313You can now cruise around your frozen 314.Pa /var 315file system at 316.Pa /mnt . 317Everything will be in the same state that it was at the time the snapshot was 318taken. 319The one exception is that any earlier snapshots will appear as zero length 320files. 321When you are done with the mounted snapshot: 322.Bd -literal 323umount /mnt 324mdconfig -d -u 4 325.Ed 326.El 327.It Cm suiddir 328A directory on the mounted file system will respond to the SUID bit 329being set, by setting the owner of any new files to be the same 330as the owner of the directory. 331New directories will inherit the bit from their parents. 332Execute bits are removed from 333the file, and it will not be given to root. 334.Pp 335This feature is designed for use on fileservers serving PC users via 336ftp, SAMBA, or netatalk. 337It provides security holes for shell users and as 338such should not be used on shell machines, especially on home directories. 339This option requires the SUIDDIR 340option in the kernel to work. 341Only UFS file systems support this option. 342See 343.Xr chmod 2 344for more information. 345.It Cm sync 346All I/O to the file system should be done synchronously. 347.It Cm update 348The same as 349.Fl u ; 350indicate that the status of an already mounted file system should be changed. 351.It Cm union 352Causes the namespace at the mount point to appear as the union 353of the mounted file system root and the existing directory. 354Lookups will be done in the mounted file system first. 355If those operations fail due to a non-existent file the underlying 356directory is then accessed. 357All creates are done in the mounted file system. 358.It Cm untrusted 359The file system is untrusted and the kernel should use more 360extensive checks on the file-system's metadata before using it. 361This option is intended to be used when mounting file systems 362from untrusted media such as USB memory sticks or other 363externally-provided media. 364.El 365.Pp 366Any additional options specific to a file system type that is not 367one of the internally known types (see the 368.Fl t 369option) may be passed as a comma separated list; these options are 370distinguished by a leading 371.Dq \&- 372(dash). 373For example, the 374.Nm 375command: 376.Bd -literal -offset indent 377mount -t cd9660 -o -e /dev/cd0 /cdrom 378.Ed 379.Pp 380causes 381.Nm 382to execute the equivalent of: 383.Bd -literal -offset indent 384/sbin/mount_cd9660 -e /dev/cd0 /cdrom 385.Ed 386.Pp 387Options that take a value are specified using the -option=value syntax: 388.Bd -literal -offset indent 389mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 390.Ed 391.Pp 392is equivalent to 393.Bd -literal -offset indent 394/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 395.Ed 396.Pp 397Additional options specific to file system types 398which are not internally known 399(see the description of the 400.Fl t 401option below) 402may be described in the manual pages for the associated 403.Pa /sbin/mount_ Ns Sy XXX 404utilities. 405.It Fl p 406Print mount information in 407.Xr fstab 5 408format. 409Implies also the 410.Fl v 411option. 412.It Fl r 413The file system is to be mounted read-only. 414Mount the file system read-only (even the super-user may not write it). 415The same as the 416.Cm ro 417argument to the 418.Fl o 419option. 420.It Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 421The argument following the 422.Fl t 423is used to indicate the file system type. 424The type 425.Cm ufs 426is the default. 427The 428.Fl t 429option can be used 430to indicate that the actions should only be taken on 431file systems of the specified type. 432More than one type may be specified in a comma separated list. 433The list of file system types can be prefixed with 434.Cm no 435to specify the file system types for which action should 436.Em not 437be taken. 438For example, the 439.Nm 440command: 441.Bd -literal -offset indent 442mount -a -t nonfs,nullfs 443.Ed 444.Pp 445mounts all file systems except those of type NFS and NULLFS. 446.Pp 447The default behavior of 448.Nm 449is to pass the 450.Fl t 451option directly to the 452.Xr nmount 2 453system call in the 454.Li fstype 455option. 456.Pp 457However, for the following file system types: 458.Cm cd9660 , 459.Cm mfs , 460.Cm msdosfs , 461.Cm nfs , 462.Cm nullfs , 463.Cm smbfs , 464.Cm udf , 465and 466.Cm unionfs 467.Nm 468will not call 469.Xr nmount 2 470directly and will instead attempt to execute a program in 471.Pa /sbin/mount_ Ns Ar type 472where 473.Ar type 474is replaced by the file system type name. 475For example, 476.Cm nfs 477file systems are mounted by the program 478.Pa /sbin/mount_nfs . 479.Pp 480Most file systems will be dynamically loaded by the kernel 481if not already present, and if the kernel module is available. 482.It Fl u 483The 484.Fl u 485flag indicates that the status of an already mounted file 486system should be changed. 487Any of the options discussed above (the 488.Fl o 489option) 490may be changed; 491also a file system can be changed from read-only to read-write 492or vice versa. 493An attempt to change from read-write to read-only will fail if any 494files on the file system are currently open for writing unless the 495.Fl f 496flag is also specified. 497The set of options is determined by applying the options specified 498in the argument to 499.Fl o 500and finally applying the 501.Fl r 502or 503.Fl w 504option. 505.It Fl v 506Verbose mode. 507If the 508.Fl v 509is used alone, show all file systems, including those that were mounted with the 510.Dv MNT_IGNORE 511flag and show additional information about each file system (including fsid 512when run by root). 513.It Fl w 514The file system object is to be read and write. 515.El 516.Sh ENVIRONMENT 517.Bl -tag -width ".Ev PATH_FSTAB" 518.It Ev PATH_FSTAB 519If the environment variable 520.Ev PATH_FSTAB 521is set, all operations are performed against the specified file. 522.Ev PATH_FSTAB 523will not be honored if the process environment or memory address space is 524considered 525.Dq tainted . 526(See 527.Xr issetugid 2 528for more information.) 529.El 530.Sh FILES 531.Bl -tag -width /etc/fstab -compact 532.It Pa /etc/fstab 533file system table 534.El 535.Sh DIAGNOSTICS 536Various, most of them are self-explanatory. 537.Pp 538.Dl XXXXX file system is not available 539.Pp 540The kernel does not support the respective file system type. 541Note that 542support for a particular file system might be provided either on a static 543(kernel compile-time), or dynamic basis (loaded as a kernel module by 544.Xr kldload 8 ) . 545.Sh SEE ALSO 546.Xr getfacl 1 , 547.Xr setfacl 1 , 548.Xr nmount 2 , 549.Xr acl 3 , 550.Xr mac 4 , 551.Xr cd9660 5 , 552.Xr devfs 5 , 553.Xr ext2fs 5 , 554.Xr fstab 5 , 555.Xr procfs 5 , 556.Xr tmpfs 5 , 557.Xr automount 8 , 558.Xr fstyp 8 , 559.Xr kldload 8 , 560.Xr mount_cd9660 8 , 561.Xr mount_msdosfs 8 , 562.Xr mount_nfs 8 , 563.Xr mount_nullfs 8 , 564.Xr mount_smbfs 8 , 565.Xr mount_udf 8 , 566.Xr mount_unionfs 8 , 567.Xr umount 8 , 568.Xr zfs 8 , 569.Xr zpool 8 570.Sh HISTORY 571A 572.Nm 573utility appeared in 574.At v1 . 575.Sh CAVEATS 576After a successful 577.Nm , 578the permissions on the original mount point determine if 579.Pa ..\& 580is accessible from the mounted file system. 581The minimum permissions for 582the mount point for traversal across the mount point in both 583directions to be possible for all users is 0111 (execute for all). 584.Pp 585Use of the 586.Nm 587is preferred over the use of the file system specific 588.Pa mount_ Ns Sy XXX 589commands. 590In particular, 591.Xr mountd 8 592gets a 593.Dv SIGHUP 594signal (that causes an update of the export list) 595only when the file system is mounted via 596.Nm . 597.Sh BUGS 598It is possible for a corrupted file system to cause a crash. 599