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 August 28, 2019 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 emptydir 166Require that the mount point directory be empty. 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 nocover 243Do not mount if the requested mount point is already 244the root of a mount point. 245.It Cm noexec 246Do not allow execution of any binaries on the mounted file system. 247This option is useful for a server that has file systems containing 248binaries for architectures other than its own. 249Note: This option was not designed as a security feature and no 250guarantee is made that it will prevent malicious code execution; for 251example, it is still possible to execute scripts which reside on a 252.Cm noexec 253mounted partition. 254.It Cm nosuid 255Do not allow set-user-identifier or set-group-identifier bits to take effect. 256Note: this option is worthless if a public available suid or sgid 257wrapper like 258.Xr suidperl 1 259is installed on your system. 260It is set automatically when the user does not have super-user privileges. 261.It Cm nosymfollow 262Do not follow symlinks 263on the mounted file system. 264.It Cm ro 265The same as 266.Fl r ; 267mount the file system read-only (even the super-user may not write it). 268.It Cm snapshot 269This option allows a snapshot of the specified file system to be taken. 270The 271.Fl u 272flag is required with this option. 273Note that snapshot files must be created in the file system that is being 274snapshotted. 275You may create up to 20 snapshots per file system. 276Active snapshots are recorded in the superblock, so they persist across unmount 277and remount operations and across system reboots. 278When you are done with a snapshot, it can be removed with the 279.Xr rm 1 280command. 281Snapshots may be removed in any order, however you may not get back all the 282space contained in the snapshot as another snapshot may claim some of the blocks 283that it is releasing. 284Note that the schg flag is set on snapshots to ensure that not even the root 285user can write to them. 286The unlink command makes an exception for snapshot files in that it allows them 287to be removed even though they have the schg flag set, so it is not necessary to 288clear the schg flag before removing a snapshot file. 289.Pp 290Once you have taken a snapshot, there are three interesting things that you can 291do with it: 292.Pp 293.Bl -enum -compact 294.It 295Run 296.Xr fsck 8 297on the snapshot file. 298Assuming that the file system was clean when it was mounted, you should always 299get a clean (and unchanging) result from running fsck on the snapshot. 300This is essentially what the background fsck process does. 301.Pp 302.It 303Run 304.Xr dump 8 305on the snapshot. 306You will get a dump that is consistent with the file system as of the timestamp 307of the snapshot. 308.Pp 309.It 310Mount the snapshot as a frozen image of the file system. 311To mount the snapshot 312.Pa /var/snapshot/snap1 : 313.Bd -literal 314mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 315mount -r /dev/md4 /mnt 316.Ed 317.Pp 318You can now cruise around your frozen 319.Pa /var 320file system at 321.Pa /mnt . 322Everything will be in the same state that it was at the time the snapshot was 323taken. 324The one exception is that any earlier snapshots will appear as zero length 325files. 326When you are done with the mounted snapshot: 327.Bd -literal 328umount /mnt 329mdconfig -d -u 4 330.Ed 331.El 332.It Cm suiddir 333A directory on the mounted file system will respond to the SUID bit 334being set, by setting the owner of any new files to be the same 335as the owner of the directory. 336New directories will inherit the bit from their parents. 337Execute bits are removed from 338the file, and it will not be given to root. 339.Pp 340This feature is designed for use on fileservers serving PC users via 341ftp, SAMBA, or netatalk. 342It provides security holes for shell users and as 343such should not be used on shell machines, especially on home directories. 344This option requires the SUIDDIR 345option in the kernel to work. 346Only UFS file systems support this option. 347See 348.Xr chmod 2 349for more information. 350.It Cm sync 351All I/O to the file system should be done synchronously. 352.It Cm update 353The same as 354.Fl u ; 355indicate that the status of an already mounted file system should be changed. 356.It Cm union 357Causes the namespace at the mount point to appear as the union 358of the mounted file system root and the existing directory. 359Lookups will be done in the mounted file system first. 360If those operations fail due to a non-existent file the underlying 361directory is then accessed. 362All creates are done in the mounted file system. 363.It Cm untrusted 364The file system is untrusted and the kernel should use more 365extensive checks on the file-system's metadata before using it. 366This option is intended to be used when mounting file systems 367from untrusted media such as USB memory sticks or other 368externally-provided media. 369.El 370.Pp 371Any additional options specific to a file system type that is not 372one of the internally known types (see the 373.Fl t 374option) may be passed as a comma separated list; these options are 375distinguished by a leading 376.Dq \&- 377(dash). 378For example, the 379.Nm 380command: 381.Bd -literal -offset indent 382mount -t cd9660 -o -e /dev/cd0 /cdrom 383.Ed 384.Pp 385causes 386.Nm 387to execute the equivalent of: 388.Bd -literal -offset indent 389/sbin/mount_cd9660 -e /dev/cd0 /cdrom 390.Ed 391.Pp 392Options that take a value are specified using the -option=value syntax: 393.Bd -literal -offset indent 394mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 395.Ed 396.Pp 397is equivalent to 398.Bd -literal -offset indent 399/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 400.Ed 401.Pp 402Additional options specific to file system types 403which are not internally known 404(see the description of the 405.Fl t 406option below) 407may be described in the manual pages for the associated 408.Pa /sbin/mount_ Ns Sy XXX 409utilities. 410.It Fl p 411Print mount information in 412.Xr fstab 5 413format. 414Implies also the 415.Fl v 416option. 417.It Fl r 418The file system is to be mounted read-only. 419Mount the file system read-only (even the super-user may not write it). 420The same as the 421.Cm ro 422argument to the 423.Fl o 424option. 425.It Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 426The argument following the 427.Fl t 428is used to indicate the file system type. 429The type 430.Cm ufs 431is the default. 432The 433.Fl t 434option can be used 435to indicate that the actions should only be taken on 436file systems of the specified type. 437More than one type may be specified in a comma separated list. 438The list of file system types can be prefixed with 439.Cm no 440to specify the file system types for which action should 441.Em not 442be taken. 443For example, the 444.Nm 445command: 446.Bd -literal -offset indent 447mount -a -t nonfs,nullfs 448.Ed 449.Pp 450mounts all file systems except those of type NFS and NULLFS. 451.Pp 452The default behavior of 453.Nm 454is to pass the 455.Fl t 456option directly to the 457.Xr nmount 2 458system call in the 459.Li fstype 460option. 461.Pp 462However, for the following file system types: 463.Cm cd9660 , 464.Cm mfs , 465.Cm msdosfs , 466.Cm nfs , 467.Cm nullfs , 468.Cm smbfs , 469.Cm udf , 470and 471.Cm unionfs 472.Nm 473will not call 474.Xr nmount 2 475directly and will instead attempt to execute a program in 476.Pa /sbin/mount_ Ns Ar type 477where 478.Ar type 479is replaced by the file system type name. 480For example, 481.Cm nfs 482file systems are mounted by the program 483.Pa /sbin/mount_nfs . 484.Pp 485Most file systems will be dynamically loaded by the kernel 486if not already present, and if the kernel module is available. 487.It Fl u 488The 489.Fl u 490flag indicates that the status of an already mounted file 491system should be changed. 492Any of the options discussed above (the 493.Fl o 494option) 495may be changed; 496also a file system can be changed from read-only to read-write 497or vice versa. 498An attempt to change from read-write to read-only will fail if any 499files on the file system are currently open for writing unless the 500.Fl f 501flag is also specified. 502The set of options is determined by applying the options specified 503in the argument to 504.Fl o 505and finally applying the 506.Fl r 507or 508.Fl w 509option. 510.It Fl v 511Verbose mode. 512If the 513.Fl v 514is used alone, show all file systems, including those that were mounted with the 515.Dv MNT_IGNORE 516flag and show additional information about each file system (including fsid 517when run by root). 518.It Fl w 519The file system object is to be read and write. 520.El 521.Sh ENVIRONMENT 522.Bl -tag -width ".Ev PATH_FSTAB" 523.It Ev PATH_FSTAB 524If the environment variable 525.Ev PATH_FSTAB 526is set, all operations are performed against the specified file. 527.Ev PATH_FSTAB 528will not be honored if the process environment or memory address space is 529considered 530.Dq tainted . 531(See 532.Xr issetugid 2 533for more information.) 534.El 535.Sh FILES 536.Bl -tag -width /etc/fstab -compact 537.It Pa /etc/fstab 538file system table 539.El 540.Sh DIAGNOSTICS 541Various, most of them are self-explanatory. 542.Pp 543.Dl XXXXX file system is not available 544.Pp 545The kernel does not support the respective file system type. 546Note that 547support for a particular file system might be provided either on a static 548(kernel compile-time), or dynamic basis (loaded as a kernel module by 549.Xr kldload 8 ) . 550.Sh SEE ALSO 551.Xr getfacl 1 , 552.Xr setfacl 1 , 553.Xr nmount 2 , 554.Xr acl 3 , 555.Xr mac 4 , 556.Xr cd9660 5 , 557.Xr devfs 5 , 558.Xr ext2fs 5 , 559.Xr fstab 5 , 560.Xr procfs 5 , 561.Xr tmpfs 5 , 562.Xr automount 8 , 563.Xr fstyp 8 , 564.Xr kldload 8 , 565.Xr mount_cd9660 8 , 566.Xr mount_msdosfs 8 , 567.Xr mount_nfs 8 , 568.Xr mount_nullfs 8 , 569.Xr mount_smbfs 8 , 570.Xr mount_udf 8 , 571.Xr mount_unionfs 8 , 572.Xr umount 8 , 573.Xr zfs 8 , 574.Xr zpool 8 575.Sh HISTORY 576A 577.Nm 578utility appeared in 579.At v1 . 580.Sh CAVEATS 581After a successful 582.Nm , 583the permissions on the original mount point determine if 584.Pa ..\& 585is accessible from the mounted file system. 586The minimum permissions for 587the mount point for traversal across the mount point in both 588directions to be possible for all users is 0111 (execute for all). 589.Pp 590Use of the 591.Nm 592is preferred over the use of the file system specific 593.Pa mount_ Ns Sy XXX 594commands. 595In particular, 596.Xr mountd 8 597gets a 598.Dv SIGHUP 599signal (that causes an update of the export list) 600only when the file system is mounted via 601.Nm . 602.Sh BUGS 603It is possible for a corrupted file system to cause a crash. 604