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.\" 30.Dd March 17, 2022 31.Dt MOUNT 8 32.Os 33.Sh NAME 34.Nm mount 35.Nd mount file systems 36.Sh SYNOPSIS 37.Nm 38.Op Fl -libxo 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 -libxo 45.Op Fl dfpruvw 46.Ar special | node 47.Nm 48.Op Fl -libxo 49.Op Fl dfpruvw 50.Op Fl o Ar options 51.Op Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 52.Ar special node 53.Sh DESCRIPTION 54The 55.Nm 56utility calls the 57.Xr nmount 2 58system call to prepare and graft a 59.Ar special 60device or the remote node (rhost:path) on to the file system tree at the point 61.Ar node . 62If either 63.Ar special 64or 65.Ar node 66are not provided, the appropriate information is taken from the 67.Xr fstab 5 68file. 69.Pp 70The system maintains a list of currently mounted file systems. 71If no arguments are given to 72.Nm , 73this list is printed. 74.Pp 75The options are as follows: 76.Bl -tag -width indent 77.It Fl -libxo 78Generate output via 79.Xr libxo 3 80in a selection of different human and machine readable formats. 81See 82.Xr xo_parse_args 3 83for details on command line arguments. 84.It Fl a 85All the file systems described in 86.Xr fstab 5 87are mounted. 88Exceptions are those marked as 89.Dq Li noauto , 90those marked as 91.Dq Li late 92(unless the 93.Fl l 94option was specified), 95those excluded by the 96.Fl t 97flag (see below), or if they are already mounted (except the 98root file system which is always remounted to preserve 99traditional single user mode behavior). 100.It Fl d 101Causes everything to be done except for the actual system call. 102This option is useful in conjunction with the 103.Fl v 104flag to 105determine what the 106.Nm 107command is trying to do. 108.It Fl F Ar fstab 109Specify the 110.Pa fstab 111file to use. 112.It Fl f 113Forces the revocation of write access when trying to downgrade 114a file system mount status from read-write to read-only. 115Also 116forces the R/W mount of an unclean file system (dangerous; use with 117caution). 118.It Fl L 119When used in conjunction with the 120.Fl a 121option, mount 122.Em only 123those file systems which are marked as 124.Dq Li late . 125.It Fl l 126When used in conjunction with the 127.Fl a 128option, also mount those file systems which are marked as 129.Dq Li late . 130.It Fl n 131For compatibility with some other implementations, this flag is 132currently a no-op. 133.It Fl o 134Options are specified with a 135.Fl o 136flag followed by a comma separated string of options. 137In case of conflicting options being specified, the rightmost option 138takes effect. 139The following options are available: 140.Bl -tag -width indent 141.It Cm acls 142Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the 143.Xr setfacl 1 144and 145.Xr getfacl 1 146commands. 147This flag is mutually exclusive with 148.Cm nfsv4acls 149flag. 150.It Cm async 151All I/O to the file system should be done asynchronously. 152This is a 153.Em dangerous 154flag to set, since it does not guarantee that the file system structure 155on the disk will remain consistent. 156For this reason, the 157.Cm async 158flag should be used sparingly, and only when some data recovery 159mechanism is present. 160.It Cm automounted 161This flag indicates that the file system was mounted by 162.Xr automountd 8 . 163Automounted file systems are automatically unmounted by 164.Xr autounmountd 8 . 165.It Cm autoro 166Mount the file system read-write. 167If that fails with an error that suggests that the media could be read-only, 168then automatically try to mount the file system read-only. 169.It Cm current 170When used with the 171.Fl u 172flag, this is the same as specifying the options currently in effect for 173the mounted file system. 174.It Cm emptydir 175Require that the mount point directory be empty. 176.It Cm force 177The same as 178.Fl f ; 179forces the revocation of write access when trying to downgrade 180a file system mount status from read-write to read-only. 181Also 182forces the R/W mount of an unclean file system (dangerous; use with caution). 183.It Cm fstab 184When used with the 185.Fl u 186flag, this is the same as specifying all the options listed in the 187.Xr fstab 5 188file for the file system. 189.It Cm late 190This file system should be skipped when 191.Nm 192is run with the 193.Fl a 194flag but without the 195.Fl l 196flag. 197.It Cm mountprog Ns = Ns Aq Ar program 198Force 199.Nm 200to use the specified program to mount the file system, instead of calling 201.Xr nmount 2 202directly. 203For example: 204.Bd -literal 205mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt 206.Ed 207.It Cm multilabel 208Enable multi-label Mandatory Access Control, or MAC, on the specified file 209system. 210If the file system supports multilabel operation, individual labels will 211be maintained for each object in the file system, rather than using a 212single label for all objects. 213An alternative to the 214.Fl l 215flag in 216.Xr tunefs 8 . 217See 218.Xr mac 4 219for more information, which cause the multilabel mount flag to be set 220automatically at mount-time. 221.It Cm nfsv4acls 222Enable NFSv4 ACLs, which can be customized via the 223.Xr setfacl 1 224and 225.Xr getfacl 1 226commands. 227This flag is mutually exclusive with 228.Cm acls 229flag. 230.It Cm noasync 231Metadata I/O should be done synchronously, while data I/O should be done 232asynchronously. 233This is the default. 234.It Cm noatime 235Do not update the file access time when reading from a file. 236This option 237is useful on file systems where there are large numbers of files and 238performance is more critical than updating the file access time (which is 239rarely ever important). 240This option is currently only supported on local file systems. 241.It Cm noauto 242This file system should be skipped when 243.Nm 244is run with the 245.Fl a 246flag. 247.It Cm noclusterr 248Disable read clustering. 249.It Cm noclusterw 250Disable write clustering. 251.It Cm nocover 252Do not mount if the requested mount point is already 253the root of a mount point. 254.It Cm noexec 255Do not allow execution of any binaries on the mounted file system. 256This option is useful for a server that has file systems containing 257binaries for architectures other than its own. 258Note: This option was not designed as a security feature and no 259guarantee is made that it will prevent malicious code execution; for 260example, it is still possible to execute scripts which reside on a 261.Cm noexec 262mounted partition. 263.It Cm nosuid 264Do not allow set-user-identifier or set-group-identifier bits to take effect. 265Note: this option is worthless if a public available suid or sgid 266wrapper is installed on your system. 267It is set automatically when the user does not have super-user privileges. 268.It Cm nosymfollow 269Do not follow symlinks 270on the mounted file system. 271.It Cm ro 272The same as 273.Fl r ; 274mount the file system read-only (even the super-user may not write it). 275.It Cm snapshot 276Take a snapshot of the specified filesystem. 277When this option is used, all other options are ignored. 278The 279.Fl u 280flag is required with this option. 281.Pp 282Snapshot files must be created in the file system that is being 283snapshotted. 284You may create up to 20 snapshots per file system. 285Active snapshots are recorded in the superblock, so they persist across unmount 286and remount operations and across system reboots. 287When you are done with a snapshot, it can be removed with the 288.Xr rm 1 289command. 290Snapshots may be removed in any order, however you may not get back all the 291space contained in the snapshot as another snapshot may claim some of the blocks 292that it is releasing. 293Note that the schg flag is set on snapshots to ensure that not even the root 294user can write to them. 295The unlink command makes an exception for snapshot files in that it allows them 296to be removed even though they have the schg flag set, so it is not necessary to 297clear the schg flag before removing a snapshot file. 298.Pp 299Once you have taken a snapshot, there are three interesting things that you can 300do with it: 301.Pp 302.Bl -enum -compact 303.It 304Run 305.Xr fsck 8 306on the snapshot file. 307Assuming that the file system was clean when it was mounted, you should always 308get a clean (and unchanging) result from running fsck on the snapshot. 309This is essentially what the background fsck process does. 310.Pp 311.It 312Run 313.Xr dump 8 314on the snapshot. 315You will get a dump that is consistent with the file system as of the timestamp 316of the snapshot. 317.Pp 318.It 319Mount the snapshot as a frozen image of the file system. 320To mount the snapshot 321.Pa /var/snapshot/snap1 : 322.Bd -literal 323mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 324mount -r /dev/md4 /mnt 325.Ed 326.Pp 327You can now cruise around your frozen 328.Pa /var 329file system at 330.Pa /mnt . 331Everything will be in the same state that it was at the time the snapshot was 332taken. 333The one exception is that any earlier snapshots will appear as zero length 334files. 335When you are done with the mounted snapshot: 336.Bd -literal 337umount /mnt 338mdconfig -d -u 4 339.Ed 340.El 341.It Cm suiddir 342A directory on the mounted file system will respond to the SUID bit 343being set, by setting the owner of any new files to be the same 344as the owner of the directory. 345New directories will inherit the bit from their parents. 346Execute bits are removed from 347the file, and it will not be given to root. 348.Pp 349This feature is designed for use on fileservers serving PC users via 350ftp, SAMBA, or netatalk. 351It provides security holes for shell users and as 352such should not be used on shell machines, especially on home directories. 353This option requires the SUIDDIR 354option in the kernel to work. 355Only UFS file systems support this option. 356See 357.Xr chmod 2 358for more information. 359.It Cm sync 360All I/O to the file system should be done synchronously. 361.It Cm update 362The same as 363.Fl u ; 364indicate that the status of an already mounted file system should be changed. 365.It Cm union 366Causes the namespace at the mount point to appear as the union 367of the mounted file system root and the existing directory. 368Lookups will be done in the mounted file system first. 369If those operations fail due to a non-existent file the underlying 370directory is then accessed. 371All creates are done in the mounted file system. 372.It Cm untrusted 373The file system is untrusted and the kernel should use more 374extensive checks on the file-system's metadata before using it. 375This option is intended to be used when mounting file systems 376from untrusted media such as USB memory sticks or other 377externally-provided media. 378.El 379.Pp 380Any additional options specific to a file system type that is not 381one of the internally known types (see the 382.Fl t 383option) may be passed as a comma separated list; these options are 384distinguished by a leading 385.Dq \&- 386(dash). 387For example, the 388.Nm 389command: 390.Bd -literal -offset indent 391mount -t cd9660 -o -e /dev/cd0 /cdrom 392.Ed 393.Pp 394causes 395.Nm 396to execute the equivalent of: 397.Bd -literal -offset indent 398/sbin/mount_cd9660 -e /dev/cd0 /cdrom 399.Ed 400.Pp 401Options that take a value are specified using the -option=value syntax: 402.Bd -literal -offset indent 403mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 404.Ed 405.Pp 406is equivalent to 407.Bd -literal -offset indent 408/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 409.Ed 410.Pp 411Additional options specific to file system types 412which are not internally known 413(see the description of the 414.Fl t 415option below) 416may be described in the manual pages for the associated 417.Pa /sbin/mount_ Ns Sy XXX 418utilities. 419.It Fl p 420Print mount information in 421.Xr fstab 5 422format. 423Implies also the 424.Fl v 425option. 426.It Fl r 427The file system is to be mounted read-only. 428Mount the file system read-only (even the super-user may not write it). 429The same as the 430.Cm ro 431argument to the 432.Fl o 433option. 434.It Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 435The argument following the 436.Fl t 437is used to indicate the file system type. 438The type 439.Cm ufs 440is the default. 441The 442.Fl t 443option can be used 444to indicate that the actions should only be taken on 445file systems of the specified type. 446More than one type may be specified in a comma separated list. 447The list of file system types can be prefixed with 448.Cm no 449to specify the file system types for which action should 450.Em not 451be taken. 452For example, the 453.Nm 454command: 455.Bd -literal -offset indent 456mount -a -t nonfs,nullfs 457.Ed 458.Pp 459mounts all file systems except those of type NFS and NULLFS. 460.Pp 461The default behavior of 462.Nm 463is to pass the 464.Fl t 465option directly to the 466.Xr nmount 2 467system call in the 468.Li fstype 469option. 470.Pp 471However, for the following file system types: 472.Cm cd9660 , 473.Cm mfs , 474.Cm msdosfs , 475.Cm nfs , 476.Cm nullfs , 477.Cm smbfs , 478.Cm udf , 479and 480.Cm unionfs 481.Nm 482will not call 483.Xr nmount 2 484directly and will instead attempt to execute a program in 485.Pa /sbin/mount_ Ns Ar type 486where 487.Ar type 488is replaced by the file system type name. 489For example, 490.Cm nfs 491file systems are mounted by the program 492.Pa /sbin/mount_nfs . 493.Pp 494Most file systems will be dynamically loaded by the kernel 495if not already present, and if the kernel module is available. 496.It Fl u 497The 498.Fl u 499flag indicates that the status of an already mounted file 500system should be changed. 501Any of the options discussed above (the 502.Fl o 503option) 504may be changed; 505also a file system can be changed from read-only to read-write 506or vice versa. 507An attempt to change from read-write to read-only will fail if any 508files on the file system are currently open for writing unless the 509.Fl f 510flag is also specified. 511The set of options is determined by applying the options specified 512in the argument to 513.Fl o 514and finally applying the 515.Fl r 516or 517.Fl w 518option. 519.It Fl v 520Verbose mode. 521If the 522.Fl v 523is used alone, show all file systems, including those that were mounted with the 524.Dv MNT_IGNORE 525flag and show additional information about each file system (including fsid 526when run by root). 527.It Fl w 528The file system object is to be read and write. 529.El 530.Sh ENVIRONMENT 531.Bl -tag -width ".Ev PATH_FSTAB" 532.It Ev PATH_FSTAB 533If the environment variable 534.Ev PATH_FSTAB 535is set, all operations are performed against the specified file. 536.Ev PATH_FSTAB 537will not be honored if the process environment or memory address space is 538considered 539.Dq tainted . 540(See 541.Xr issetugid 2 542for more information.) 543.El 544.Sh FILES 545.Bl -tag -width /etc/fstab -compact 546.It Pa /etc/fstab 547file system table 548.El 549.Sh DIAGNOSTICS 550Various, most of them are self-explanatory. 551.Pp 552.Dl XXXXX file system is not available 553.Pp 554The kernel does not support the respective file system type. 555Note that 556support for a particular file system might be provided either on a static 557(kernel compile-time), or dynamic basis (loaded as a kernel module by 558.Xr kldload 8 ) . 559.Sh SEE ALSO 560.Xr getfacl 1 , 561.Xr setfacl 1 , 562.Xr nmount 2 , 563.Xr acl 3 , 564.Xr libxo 3 , 565.Xr xo_parse_args 3 , 566.Xr mac 4 , 567.Xr cd9660 5 , 568.Xr devfs 5 , 569.Xr ext2fs 5 , 570.Xr fstab 5 , 571.Xr procfs 5 , 572.Xr tmpfs 5 , 573.Xr automount 8 , 574.Xr fstyp 8 , 575.Xr kldload 8 , 576.Xr mount_cd9660 8 , 577.Xr mount_msdosfs 8 , 578.Xr mount_nfs 8 , 579.Xr mount_nullfs 8 , 580.Xr mount_smbfs 8 , 581.Xr mount_udf 8 , 582.Xr mount_unionfs 8 , 583.Xr umount 8 , 584.Xr zfs 8 , 585.Xr zpool 8 586.Sh HISTORY 587A 588.Nm 589utility appeared in 590.At v1 . 591.Sh CAVEATS 592After a successful 593.Nm , 594the permissions on the original mount point determine if 595.Pa ..\& 596is accessible from the mounted file system. 597The minimum permissions for 598the mount point for traversal across the mount point in both 599directions to be possible for all users is 0111 (execute for all). 600.Pp 601Use of the 602.Nm 603is preferred over the use of the file system specific 604.Pa mount_ Ns Sy XXX 605commands. 606In particular, 607.Xr mountd 8 608gets a 609.Dv SIGHUP 610signal (that causes an update of the export list) 611only when the file system is mounted via 612.Nm . 613.Sh BUGS 614It is possible for a corrupted file system to cause a crash. 615