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 17, 2022 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 -libxo 40.Op Fl adflpruvw 41.Op Fl F Ar fstab 42.Op Fl o Ar options 43.Op Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 44.Nm 45.Op Fl -libxo 46.Op Fl dfpruvw 47.Ar special | node 48.Nm 49.Op Fl -libxo 50.Op Fl dfpruvw 51.Op Fl o Ar options 52.Op Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 53.Ar special node 54.Sh DESCRIPTION 55The 56.Nm 57utility calls the 58.Xr nmount 2 59system call to prepare and graft a 60.Ar special 61device or the remote node (rhost:path) on to the file system tree at the point 62.Ar node . 63If either 64.Ar special 65or 66.Ar node 67are not provided, the appropriate information is taken from the 68.Xr fstab 5 69file. 70.Pp 71The system maintains a list of currently mounted file systems. 72If no arguments are given to 73.Nm , 74this list is printed. 75.Pp 76The options are as follows: 77.Bl -tag -width indent 78.It Fl -libxo 79Generate output via 80.Xr libxo 3 81in a selection of different human and machine readable formats. 82See 83.Xr xo_parse_args 3 84for details on command line arguments. 85.It Fl a 86All the file systems described in 87.Xr fstab 5 88are mounted. 89Exceptions are those marked as 90.Dq Li noauto , 91those marked as 92.Dq Li late 93(unless the 94.Fl l 95option was specified), 96those excluded by the 97.Fl t 98flag (see below), or if they are already mounted (except the 99root file system which is always remounted to preserve 100traditional single user mode behavior). 101.It Fl d 102Causes everything to be done except for the actual system call. 103This option is useful in conjunction with the 104.Fl v 105flag to 106determine what the 107.Nm 108command is trying to do. 109.It Fl F Ar fstab 110Specify the 111.Pa fstab 112file to use. 113.It Fl f 114Forces the revocation of write access when trying to downgrade 115a file system mount status from read-write to read-only. 116Also 117forces the R/W mount of an unclean file system (dangerous; use with 118caution). 119.It Fl L 120When used in conjunction with the 121.Fl a 122option, mount 123.Em only 124those file systems which are marked as 125.Dq Li late . 126.It Fl l 127When used in conjunction with the 128.Fl a 129option, also mount those file systems which are marked as 130.Dq Li late . 131.It Fl n 132For compatibility with some other implementations, this flag is 133currently a no-op. 134.It Fl o 135Options are specified with a 136.Fl o 137flag followed by a comma separated string of options. 138In case of conflicting options being specified, the rightmost option 139takes effect. 140The following options are available: 141.Bl -tag -width indent 142.It Cm acls 143Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the 144.Xr setfacl 1 145and 146.Xr getfacl 1 147commands. 148This flag is mutually exclusive with 149.Cm nfsv4acls 150flag. 151.It Cm async 152All I/O to the file system should be done asynchronously. 153This is a 154.Em dangerous 155flag to set, since it does not guarantee that the file system structure 156on the disk will remain consistent. 157For this reason, the 158.Cm async 159flag should be used sparingly, and only when some data recovery 160mechanism is present. 161.It Cm automounted 162This flag indicates that the file system was mounted by 163.Xr automountd 8 . 164Automounted file systems are automatically unmounted by 165.Xr autounmountd 8 . 166.It Cm autoro 167Mount the file system read-write. 168If that fails with an error that suggests that the media could be read-only, 169then automatically try to mount the file system read-only. 170.It Cm current 171When used with the 172.Fl u 173flag, this is the same as specifying the options currently in effect for 174the mounted file system. 175.It Cm emptydir 176Require that the mount point directory be empty. 177.It Cm force 178The same as 179.Fl f ; 180forces the revocation of write access when trying to downgrade 181a file system mount status from read-write to read-only. 182Also 183forces the R/W mount of an unclean file system (dangerous; use with caution). 184.It Cm fstab 185When used with the 186.Fl u 187flag, this is the same as specifying all the options listed in the 188.Xr fstab 5 189file for the file system. 190.It Cm late 191This file system should be skipped when 192.Nm 193is run with the 194.Fl a 195flag but without the 196.Fl l 197flag. 198.It Cm mountprog Ns = Ns Aq Ar program 199Force 200.Nm 201to use the specified program to mount the file system, instead of calling 202.Xr nmount 2 203directly. 204For example: 205.Bd -literal 206mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt 207.Ed 208.It Cm multilabel 209Enable multi-label Mandatory Access Control, or MAC, on the specified file 210system. 211If the file system supports multilabel operation, individual labels will 212be maintained for each object in the file system, rather than using a 213single label for all objects. 214An alternative to the 215.Fl l 216flag in 217.Xr tunefs 8 . 218See 219.Xr mac 4 220for more information, which cause the multilabel mount flag to be set 221automatically at mount-time. 222.It Cm nfsv4acls 223Enable NFSv4 ACLs, which can be customized via the 224.Xr setfacl 1 225and 226.Xr getfacl 1 227commands. 228This flag is mutually exclusive with 229.Cm acls 230flag. 231.It Cm noasync 232Metadata I/O should be done synchronously, while data I/O should be done 233asynchronously. 234This is the default. 235.It Cm noatime 236Do not update the file access time when reading from a file. 237This option 238is useful on file systems where there are large numbers of files and 239performance is more critical than updating the file access time (which is 240rarely ever important). 241This option is currently only supported on local file systems. 242.It Cm noauto 243This file system should be skipped when 244.Nm 245is run with the 246.Fl a 247flag. 248.It Cm noclusterr 249Disable read clustering. 250.It Cm noclusterw 251Disable write clustering. 252.It Cm nocover 253Do not mount if the requested mount point is already 254the root of a mount point. 255.It Cm noexec 256Do not allow execution of any binaries on the mounted file system. 257This option is useful for a server that has file systems containing 258binaries for architectures other than its own. 259Note: This option was not designed as a security feature and no 260guarantee is made that it will prevent malicious code execution; for 261example, it is still possible to execute scripts which reside on a 262.Cm noexec 263mounted partition. 264.It Cm nosuid 265Do not allow set-user-identifier or set-group-identifier bits to take effect. 266Note: this option is worthless if a public available suid or sgid 267wrapper like 268.Xr suidperl 1 269is installed on your system. 270It is set automatically when the user does not have super-user privileges. 271.It Cm nosymfollow 272Do not follow symlinks 273on the mounted file system. 274.It Cm ro 275The same as 276.Fl r ; 277mount the file system read-only (even the super-user may not write it). 278.It Cm snapshot 279Take a snapshot of the specified filesystem. 280When this option is used, all other options are ignored. 281The 282.Fl u 283flag is required with this option. 284.Pp 285Snapshot files must be created in the file system that is being 286snapshotted. 287You may create up to 20 snapshots per file system. 288Active snapshots are recorded in the superblock, so they persist across unmount 289and remount operations and across system reboots. 290When you are done with a snapshot, it can be removed with the 291.Xr rm 1 292command. 293Snapshots may be removed in any order, however you may not get back all the 294space contained in the snapshot as another snapshot may claim some of the blocks 295that it is releasing. 296Note that the schg flag is set on snapshots to ensure that not even the root 297user can write to them. 298The unlink command makes an exception for snapshot files in that it allows them 299to be removed even though they have the schg flag set, so it is not necessary to 300clear the schg flag before removing a snapshot file. 301.Pp 302Once you have taken a snapshot, there are three interesting things that you can 303do with it: 304.Pp 305.Bl -enum -compact 306.It 307Run 308.Xr fsck 8 309on the snapshot file. 310Assuming that the file system was clean when it was mounted, you should always 311get a clean (and unchanging) result from running fsck on the snapshot. 312This is essentially what the background fsck process does. 313.Pp 314.It 315Run 316.Xr dump 8 317on the snapshot. 318You will get a dump that is consistent with the file system as of the timestamp 319of the snapshot. 320.Pp 321.It 322Mount the snapshot as a frozen image of the file system. 323To mount the snapshot 324.Pa /var/snapshot/snap1 : 325.Bd -literal 326mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 327mount -r /dev/md4 /mnt 328.Ed 329.Pp 330You can now cruise around your frozen 331.Pa /var 332file system at 333.Pa /mnt . 334Everything will be in the same state that it was at the time the snapshot was 335taken. 336The one exception is that any earlier snapshots will appear as zero length 337files. 338When you are done with the mounted snapshot: 339.Bd -literal 340umount /mnt 341mdconfig -d -u 4 342.Ed 343.El 344.It Cm suiddir 345A directory on the mounted file system will respond to the SUID bit 346being set, by setting the owner of any new files to be the same 347as the owner of the directory. 348New directories will inherit the bit from their parents. 349Execute bits are removed from 350the file, and it will not be given to root. 351.Pp 352This feature is designed for use on fileservers serving PC users via 353ftp, SAMBA, or netatalk. 354It provides security holes for shell users and as 355such should not be used on shell machines, especially on home directories. 356This option requires the SUIDDIR 357option in the kernel to work. 358Only UFS file systems support this option. 359See 360.Xr chmod 2 361for more information. 362.It Cm sync 363All I/O to the file system should be done synchronously. 364.It Cm update 365The same as 366.Fl u ; 367indicate that the status of an already mounted file system should be changed. 368.It Cm union 369Causes the namespace at the mount point to appear as the union 370of the mounted file system root and the existing directory. 371Lookups will be done in the mounted file system first. 372If those operations fail due to a non-existent file the underlying 373directory is then accessed. 374All creates are done in the mounted file system. 375.It Cm untrusted 376The file system is untrusted and the kernel should use more 377extensive checks on the file-system's metadata before using it. 378This option is intended to be used when mounting file systems 379from untrusted media such as USB memory sticks or other 380externally-provided media. 381.El 382.Pp 383Any additional options specific to a file system type that is not 384one of the internally known types (see the 385.Fl t 386option) may be passed as a comma separated list; these options are 387distinguished by a leading 388.Dq \&- 389(dash). 390For example, the 391.Nm 392command: 393.Bd -literal -offset indent 394mount -t cd9660 -o -e /dev/cd0 /cdrom 395.Ed 396.Pp 397causes 398.Nm 399to execute the equivalent of: 400.Bd -literal -offset indent 401/sbin/mount_cd9660 -e /dev/cd0 /cdrom 402.Ed 403.Pp 404Options that take a value are specified using the -option=value syntax: 405.Bd -literal -offset indent 406mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 407.Ed 408.Pp 409is equivalent to 410.Bd -literal -offset indent 411/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 412.Ed 413.Pp 414Additional options specific to file system types 415which are not internally known 416(see the description of the 417.Fl t 418option below) 419may be described in the manual pages for the associated 420.Pa /sbin/mount_ Ns Sy XXX 421utilities. 422.It Fl p 423Print mount information in 424.Xr fstab 5 425format. 426Implies also the 427.Fl v 428option. 429.It Fl r 430The file system is to be mounted read-only. 431Mount the file system read-only (even the super-user may not write it). 432The same as the 433.Cm ro 434argument to the 435.Fl o 436option. 437.It Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ... 438The argument following the 439.Fl t 440is used to indicate the file system type. 441The type 442.Cm ufs 443is the default. 444The 445.Fl t 446option can be used 447to indicate that the actions should only be taken on 448file systems of the specified type. 449More than one type may be specified in a comma separated list. 450The list of file system types can be prefixed with 451.Cm no 452to specify the file system types for which action should 453.Em not 454be taken. 455For example, the 456.Nm 457command: 458.Bd -literal -offset indent 459mount -a -t nonfs,nullfs 460.Ed 461.Pp 462mounts all file systems except those of type NFS and NULLFS. 463.Pp 464The default behavior of 465.Nm 466is to pass the 467.Fl t 468option directly to the 469.Xr nmount 2 470system call in the 471.Li fstype 472option. 473.Pp 474However, for the following file system types: 475.Cm cd9660 , 476.Cm mfs , 477.Cm msdosfs , 478.Cm nfs , 479.Cm nullfs , 480.Cm smbfs , 481.Cm udf , 482and 483.Cm unionfs 484.Nm 485will not call 486.Xr nmount 2 487directly and will instead attempt to execute a program in 488.Pa /sbin/mount_ Ns Ar type 489where 490.Ar type 491is replaced by the file system type name. 492For example, 493.Cm nfs 494file systems are mounted by the program 495.Pa /sbin/mount_nfs . 496.Pp 497Most file systems will be dynamically loaded by the kernel 498if not already present, and if the kernel module is available. 499.It Fl u 500The 501.Fl u 502flag indicates that the status of an already mounted file 503system should be changed. 504Any of the options discussed above (the 505.Fl o 506option) 507may be changed; 508also a file system can be changed from read-only to read-write 509or vice versa. 510An attempt to change from read-write to read-only will fail if any 511files on the file system are currently open for writing unless the 512.Fl f 513flag is also specified. 514The set of options is determined by applying the options specified 515in the argument to 516.Fl o 517and finally applying the 518.Fl r 519or 520.Fl w 521option. 522.It Fl v 523Verbose mode. 524If the 525.Fl v 526is used alone, show all file systems, including those that were mounted with the 527.Dv MNT_IGNORE 528flag and show additional information about each file system (including fsid 529when run by root). 530.It Fl w 531The file system object is to be read and write. 532.El 533.Sh ENVIRONMENT 534.Bl -tag -width ".Ev PATH_FSTAB" 535.It Ev PATH_FSTAB 536If the environment variable 537.Ev PATH_FSTAB 538is set, all operations are performed against the specified file. 539.Ev PATH_FSTAB 540will not be honored if the process environment or memory address space is 541considered 542.Dq tainted . 543(See 544.Xr issetugid 2 545for more information.) 546.El 547.Sh FILES 548.Bl -tag -width /etc/fstab -compact 549.It Pa /etc/fstab 550file system table 551.El 552.Sh DIAGNOSTICS 553Various, most of them are self-explanatory. 554.Pp 555.Dl XXXXX file system is not available 556.Pp 557The kernel does not support the respective file system type. 558Note that 559support for a particular file system might be provided either on a static 560(kernel compile-time), or dynamic basis (loaded as a kernel module by 561.Xr kldload 8 ) . 562.Sh SEE ALSO 563.Xr getfacl 1 , 564.Xr setfacl 1 , 565.Xr nmount 2 , 566.Xr acl 3 , 567.Xr libxo 3 , 568.Xr xo_parse_args 3 , 569.Xr mac 4 , 570.Xr cd9660 5 , 571.Xr devfs 5 , 572.Xr ext2fs 5 , 573.Xr fstab 5 , 574.Xr procfs 5 , 575.Xr tmpfs 5 , 576.Xr automount 8 , 577.Xr fstyp 8 , 578.Xr kldload 8 , 579.Xr mount_cd9660 8 , 580.Xr mount_msdosfs 8 , 581.Xr mount_nfs 8 , 582.Xr mount_nullfs 8 , 583.Xr mount_smbfs 8 , 584.Xr mount_udf 8 , 585.Xr mount_unionfs 8 , 586.Xr umount 8 , 587.Xr zfs 8 , 588.Xr zpool 8 589.Sh HISTORY 590A 591.Nm 592utility appeared in 593.At v1 . 594.Sh CAVEATS 595After a successful 596.Nm , 597the permissions on the original mount point determine if 598.Pa ..\& 599is accessible from the mounted file system. 600The minimum permissions for 601the mount point for traversal across the mount point in both 602directions to be possible for all users is 0111 (execute for all). 603.Pp 604Use of the 605.Nm 606is preferred over the use of the file system specific 607.Pa mount_ Ns Sy XXX 608commands. 609In particular, 610.Xr mountd 8 611gets a 612.Dv SIGHUP 613signal (that causes an update of the export list) 614only when the file system is mounted via 615.Nm . 616.Sh BUGS 617It is possible for a corrupted file system to cause a crash. 618