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 October 13, 2015 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 current 159When used with the 160.Fl u 161flag, this is the same as specifying the options currently in effect for 162the mounted file system. 163.It Cm force 164The same as 165.Fl f ; 166forces the revocation of write access when trying to downgrade 167a file system mount status from read-write to read-only. 168Also 169forces the R/W mount of an unclean file system (dangerous; use with caution). 170.It Cm fstab 171When used with the 172.Fl u 173flag, this is the same as specifying all the options listed in the 174.Xr fstab 5 175file for the file system. 176.It Cm late 177This file system should be skipped when 178.Nm 179is run with the 180.Fl a 181flag but without the 182.Fl l 183flag. 184.It Cm mountprog Ns = Ns Aq Ar program 185Force 186.Nm 187to use the specified program to mount the file system, instead of calling 188.Xr nmount 2 189directly. 190For example: 191.Bd -literal 192mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt 193.Ed 194.It Cm multilabel 195Enable multi-label Mandatory Access Control, or MAC, on the specified file 196system. 197If the file system supports multilabel operation, individual labels will 198be maintained for each object in the file system, rather than using a 199single label for all objects. 200An alternative to the 201.Fl l 202flag in 203.Xr tunefs 8 . 204See 205.Xr mac 4 206for more information, which cause the multilabel mount flag to be set 207automatically at mount-time. 208.It Cm nfsv4acls 209Enable NFSv4 ACLs, which can be customized via the 210.Xr setfacl 1 211and 212.Xr getfacl 1 213commands. 214This flag is mutually exclusive with 215.Cm acls 216flag. 217.It Cm noasync 218Metadata I/O should be done synchronously, while data I/O should be done 219asynchronously. 220This is the default. 221.It Cm noatime 222Do not update the file access time when reading from a file. 223This option 224is useful on file systems where there are large numbers of files and 225performance is more critical than updating the file access time (which is 226rarely ever important). 227This option is currently only supported on local file systems. 228.It Cm noauto 229This file system should be skipped when 230.Nm 231is run with the 232.Fl a 233flag. 234.It Cm noclusterr 235Disable read clustering. 236.It Cm noclusterw 237Disable write clustering. 238.It Cm noexec 239Do not allow execution of any binaries on the mounted file system. 240This option is useful for a server that has file systems containing 241binaries for architectures other than its own. 242Note: This option was not designed as a security feature and no 243guarantee is made that it will prevent malicious code execution; for 244example, it is still possible to execute scripts which reside on a 245.Cm noexec 246mounted partition. 247.It Cm nosuid 248Do not allow set-user-identifier or set-group-identifier bits to take effect. 249Note: this option is worthless if a public available suid or sgid 250wrapper like 251.Xr suidperl 1 252is installed on your system. 253It is set automatically when the user does not have super-user privileges. 254.It Cm nosymfollow 255Do not follow symlinks 256on the mounted file system. 257.It Cm ro 258The same as 259.Fl r ; 260mount the file system read-only (even the super-user may not write it). 261.It Cm snapshot 262This option allows a snapshot of the specified file system to be taken. 263The 264.Fl u 265flag is required with this option. 266Note that snapshot files must be created in the file system that is being 267snapshotted. 268You may create up to 20 snapshots per file system. 269Active snapshots are recorded in the superblock, so they persist across unmount 270and remount operations and across system reboots. 271When you are done with a snapshot, it can be removed with the 272.Xr rm 1 273command. 274Snapshots may be removed in any order, however you may not get back all the 275space contained in the snapshot as another snapshot may claim some of the blocks 276that it is releasing. 277Note that the schg flag is set on snapshots to ensure that not even the root 278user can write to them. 279The unlink command makes an exception for snapshot files in that it allows them 280to be removed even though they have the schg flag set, so it is not necessary to 281clear the schg flag before removing a snapshot file. 282.Pp 283Once you have taken a snapshot, there are three interesting things that you can 284do with it: 285.Pp 286.Bl -enum -compact 287.It 288Run 289.Xr fsck 8 290on the snapshot file. 291Assuming that the file system was clean when it was mounted, you should always 292get a clean (and unchanging) result from running fsck on the snapshot. 293This is essentially what the background fsck process does. 294.Pp 295.It 296Run 297.Xr dump 8 298on the snapshot. 299You will get a dump that is consistent with the file system as of the timestamp 300of the snapshot. 301.Pp 302.It 303Mount the snapshot as a frozen image of the file system. 304To mount the snapshot 305.Pa /var/snapshot/snap1 : 306.Bd -literal 307mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 308mount -r /dev/md4 /mnt 309.Ed 310.Pp 311You can now cruise around your frozen 312.Pa /var 313file system at 314.Pa /mnt . 315Everything will be in the same state that it was at the time the snapshot was 316taken. 317The one exception is that any earlier snapshots will appear as zero length 318files. 319When you are done with the mounted snapshot: 320.Bd -literal 321umount /mnt 322mdconfig -d -u 4 323.Ed 324.El 325.It Cm suiddir 326A directory on the mounted file system will respond to the SUID bit 327being set, by setting the owner of any new files to be the same 328as the owner of the directory. 329New directories will inherit the bit from their parents. 330Execute bits are removed from 331the file, and it will not be given to root. 332.Pp 333This feature is designed for use on fileservers serving PC users via 334ftp, SAMBA, or netatalk. 335It provides security holes for shell users and as 336such should not be used on shell machines, especially on home directories. 337This option requires the SUIDDIR 338option in the kernel to work. 339Only UFS file systems support this option. 340See 341.Xr chmod 2 342for more information. 343.It Cm sync 344All 345.Tn I/O 346to 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.El 359.Pp 360Any additional options specific to a file system type that is not 361one of the internally known types (see the 362.Fl t 363option) may be passed as a comma separated list; these options are 364distinguished by a leading 365.Dq \&- 366(dash). 367For example, the 368.Nm 369command: 370.Bd -literal -offset indent 371mount -t cd9660 -o -e /dev/cd0 /cdrom 372.Ed 373.Pp 374causes 375.Nm 376to execute the equivalent of: 377.Bd -literal -offset indent 378/sbin/mount_cd9660 -e /dev/cd0 /cdrom 379.Ed 380.Pp 381Options that take a value are specified using the -option=value syntax: 382.Bd -literal -offset indent 383mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 384.Ed 385.Pp 386is equivalent to 387.Bd -literal -offset indent 388/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 389.Ed 390.Pp 391Additional options specific to file system types 392which are not internally known 393(see the description of the 394.Fl t 395option below) 396may be described in the manual pages for the associated 397.Pa /sbin/mount_ Ns Sy XXX 398utilities. 399.It Fl p 400Print mount information in 401.Xr fstab 5 402format. 403Implies also the 404.Fl v 405option. 406.It Fl r 407The file system is to be mounted read-only. 408Mount the file system read-only (even the super-user may not write it). 409The same as the 410.Cm ro 411argument to the 412.Fl o 413option. 414.It Fl t Cm ufs | Ar external_type 415The argument following the 416.Fl t 417is used to indicate the file system type. 418The type 419.Cm ufs 420is the default. 421The 422.Fl t 423option can be used 424to indicate that the actions should only be taken on 425file systems of the specified type. 426More than one type may be specified in a comma separated list. 427The list of file system types can be prefixed with 428.Dq Li no 429to specify the file system types for which action should 430.Em not 431be taken. 432For example, the 433.Nm 434command: 435.Bd -literal -offset indent 436mount -a -t nonfs,nullfs 437.Ed 438.Pp 439mounts all file systems except those of type 440.Tn NFS 441and 442.Tn NULLFS . 443.Pp 444The default behavior of 445.Nm 446is to pass the 447.Fl t 448option directly to the 449.Xr nmount 2 450system call in the 451.Li fstype 452option. 453.Pp 454However, for the following file system types: 455.Cm cd9660 , 456.Cm mfs , 457.Cm msdosfs , 458.Cm nfs , 459.Cm nullfs , 460.Cm smbfs , 461.Cm udf , 462and 463.Cm unionfs . 464.Nm 465will not call 466.Xr nmount 2 467directly and will instead attempt to execute a program in 468.Pa /sbin/mount_ Ns Sy XXX 469where 470.Sy XXX 471is replaced by the file system type name. 472For example, nfs file systems are mounted by the program 473.Pa /sbin/mount_nfs . 474.Pp 475Most file systems will be dynamically loaded by the kernel 476if not already present, and if the kernel module is available. 477.It Fl u 478The 479.Fl u 480flag indicates that the status of an already mounted file 481system should be changed. 482Any of the options discussed above (the 483.Fl o 484option) 485may be changed; 486also a file system can be changed from read-only to read-write 487or vice versa. 488An attempt to change from read-write to read-only will fail if any 489files on the file system are currently open for writing unless the 490.Fl f 491flag is also specified. 492The set of options is determined by applying the options specified 493in the argument to 494.Fl o 495and finally applying the 496.Fl r 497or 498.Fl w 499option. 500.It Fl v 501Verbose mode. 502If the 503.Fl v 504is used alone, show all file systems, including those that were mounted with the 505.Dv MNT_IGNORE 506flag and show additional information about each file system (including fsid 507when run by root). 508.It Fl w 509The file system object is to be read and write. 510.El 511.Sh ENVIRONMENT 512.Bl -tag -width ".Ev PATH_FSTAB" 513.It Ev PATH_FSTAB 514If the environment variable 515.Ev PATH_FSTAB 516is set, all operations are performed against the specified file. 517.Ev PATH_FSTAB 518will not be honored if the process environment or memory address space is 519considered 520.Dq tainted . 521(See 522.Xr issetugid 2 523for more information.) 524.El 525.Sh FILES 526.Bl -tag -width /etc/fstab -compact 527.It Pa /etc/fstab 528file system table 529.El 530.Sh DIAGNOSTICS 531Various, most of them are self-explanatory. 532.Pp 533.Dl XXXXX file system is not available 534.Pp 535The kernel does not support the respective file system type. 536Note that 537support for a particular file system might be provided either on a static 538(kernel compile-time), or dynamic basis (loaded as a kernel module by 539.Xr kldload 8 ) . 540.Sh SEE ALSO 541.Xr getfacl 1 , 542.Xr setfacl 1 , 543.Xr nmount 2 , 544.Xr acl 3 , 545.Xr mac 4 , 546.Xr devfs 5 , 547.Xr ext2fs 5 , 548.Xr fstab 5 , 549.Xr procfs 5 , 550.Xr tmpfs 5 , 551.Xr automount 8 , 552.Xr fstyp 8 , 553.Xr kldload 8 , 554.Xr mount_cd9660 8 , 555.Xr mount_msdosfs 8 , 556.Xr mount_nfs 8 , 557.Xr mount_nullfs 8 , 558.Xr mount_smbfs 8 , 559.Xr mount_udf 8 , 560.Xr mount_unionfs 8 , 561.Xr umount 8 , 562.Xr zfs 8 , 563.Xr zpool 8 564.Sh HISTORY 565A 566.Nm 567utility appeared in 568.At v1 . 569.Sh CAVEATS 570After a successful 571.Nm , 572the permissions on the original mount point determine if 573.Pa ..\& 574is accessible from the mounted file system. 575The minimum permissions for 576the mount point for traversal across the mount point in both 577directions to be possible for all users is 0111 (execute for all). 578.Pp 579Use of the 580.Nm 581is preferred over the use of the file system specific 582.Pa mount_ Ns Sy XXX 583commands. 584In particular, 585.Xr mountd 8 586gets a 587.Dv SIGHUP 588signal (that causes an update of the export list) 589only when the file system is mounted via 590.Nm . 591.Sh BUGS 592It is possible for a corrupted file system to cause a crash. 593