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.\" 4. 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 11, 2008 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, also mount those file systems which are marked as 113.Dq Li late . 114.It Fl o 115Options are specified with a 116.Fl o 117flag followed by a comma separated string of options. 118In case of conflicting options being specified, the rightmost option 119takes effect. 120The following options are available: 121.Bl -tag -width indent 122.It Cm acls 123Enable Access Control Lists, or ACLS, which can be customized via the 124.Xr setfacl 1 125and 126.Xr getfacl 1 127commands. 128.It Cm async 129All 130.Tn I/O 131to the file system should be done asynchronously. 132This is a 133.Em dangerous 134flag to set, since it does not guarantee that the file system structure 135on the disk will remain consistent. 136For this reason, the 137.Cm async 138flag should be used sparingly, and only when some data recovery 139mechanism is present. 140.It Cm current 141When used with the 142.Fl u 143flag, this is the same as specifying the options currently in effect for 144the mounted file system. 145.It Cm force 146The same as 147.Fl f ; 148forces the revocation of write access when trying to downgrade 149a file system mount status from read-write to read-only. 150Also 151forces the R/W mount of an unclean file system (dangerous; use with caution). 152.It Cm fstab 153When used with the 154.Fl u 155flag, this is the same as specifying all the options listed in the 156.Xr fstab 5 157file for the file system. 158.It Cm late 159This file system should be skipped when 160.Nm 161is run with the 162.Fl a 163flag but without the 164.Fl l 165flag. 166.It Cm mountprog Ns = Ns Aq Ar program 167Force 168.Nm 169to use the specified program to mount the file system, instead of calling 170.Xr nmount 2 171directly. For example: 172.Bd -literal 173mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt 174.Ed 175.It Cm multilabel 176Enable multi-label Mandatory Access Control, or MAC, on the specified file 177system. 178If the file system supports multilabel operation, individual labels will 179be maintained for each object in the file system, rather than using a 180single label for all objects. 181An alternative to the 182.Fl l 183flag in 184.Xr tunefs 8 . 185See 186.Xr mac 4 187for more information, which cause the multilabel mount flag to be set 188automatically at mount-time. 189.It Cm noasync 190Metadata I/O should be done synchronously, while data I/O should be done 191asynchronously. 192This is the default. 193.It Cm noatime 194Do not update the file access time when reading from a file. 195This option 196is useful on file systems where there are large numbers of files and 197performance is more critical than updating the file access time (which is 198rarely ever important). 199This option is currently only supported on local file systems. 200.It Cm noauto 201This file system should be skipped when 202.Nm 203is run with the 204.Fl a 205flag. 206.It Cm noclusterr 207Disable read clustering. 208.It Cm noclusterw 209Disable write clustering. 210.It Cm noexec 211Do not allow execution of any binaries on the mounted file system. 212This option is useful for a server that has file systems containing 213binaries for architectures other than its own. 214Note: This option was not designed as a security feature and no 215guarantee is made that it will prevent malicious code execution; for 216example, it is still possible to execute scripts which reside on a 217.Cm noexec 218mounted partition. 219.It Cm nosuid 220Do not allow set-user-identifier or set-group-identifier bits to take effect. 221Note: this option is worthless if a public available suid or sgid 222wrapper like 223.Xr suidperl 1 224is installed on your system. 225It is set automatically when the user does not have super-user privileges. 226.It Cm nosymfollow 227Do not follow symlinks 228on the mounted file system. 229.It Cm ro 230The same as 231.Fl r ; 232mount the file system read-only (even the super-user may not write it). 233.It Cm snapshot 234This option allows a snapshot of the specified file system to be taken. 235The 236.Fl u 237flag is required with this option. 238Note that snapshot files must be created in the file system that is being 239snapshotted. 240You may create up to 20 snapshots per file system. 241Active snapshots are recorded in the superblock, so they persist across unmount 242and remount operations and across system reboots. 243When you are done with a snapshot, it can be removed with the 244.Xr rm 1 245command. 246Snapshots may be removed in any order, however you may not get back all the 247space contained in the snapshot as another snapshot may claim some of the blocks 248that it is releasing. 249Note that the schg flag is set on snapshots to ensure that not even the root 250user can write to them. 251The unlink command makes an exception for snapshot files in that it allows them 252to be removed even though they have the schg flag set, so it is not necessary to 253clear the schg flag before removing a snapshot file. 254.Pp 255Once you have taken a snapshot, there are three interesting things that you can 256do with it: 257.Pp 258.Bl -enum -compact 259.It 260Run 261.Xr fsck 8 262on the snapshot file. 263Assuming that the file system was clean when it was mounted, you should always 264get a clean (and unchanging) result from running fsck on the snapshot. 265This is essentially what the background fsck process does. 266.Pp 267.It 268Run 269.Xr dump 8 270on the snapshot. 271You will get a dump that is consistent with the file system as of the timestamp 272of the snapshot. 273.Pp 274.It 275Mount the snapshot as a frozen image of the file system. 276To mount the snapshot 277.Pa /var/snapshot/snap1 : 278.Bd -literal 279mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 280mount -r /dev/md4 /mnt 281.Ed 282.Pp 283You can now cruise around your frozen 284.Pa /var 285file system at 286.Pa /mnt . 287Everything will be in the same state that it was at the time the snapshot was 288taken. 289The one exception is that any earlier snapshots will appear as zero length 290files. 291When you are done with the mounted snapshot: 292.Bd -literal 293umount /mnt 294mdconfig -d -u 4 295.Ed 296.Pp 297Further details can be found in the file at 298.Pa /usr/src/sys/ufs/ffs/README.snapshot . 299.El 300.It Cm suiddir 301A directory on the mounted file system will respond to the SUID bit 302being set, by setting the owner of any new files to be the same 303as the owner of the directory. 304New directories will inherit the bit from their parents. 305Execute bits are removed from 306the file, and it will not be given to root. 307.Pp 308This feature is designed for use on fileservers serving PC users via 309ftp, SAMBA, or netatalk. 310It provides security holes for shell users and as 311such should not be used on shell machines, especially on home directories. 312This option requires the SUIDDIR 313option in the kernel to work. 314Only UFS file systems support this option. 315See 316.Xr chmod 2 317for more information. 318.It Cm sync 319All 320.Tn I/O 321to the file system should be done synchronously. 322.It Cm update 323The same as 324.Fl u ; 325indicate that the status of an already mounted file system should be changed. 326.It Cm union 327Causes the namespace at the mount point to appear as the union 328of the mounted file system root and the existing directory. 329Lookups will be done in the mounted file system first. 330If those operations fail due to a non-existent file the underlying 331directory is then accessed. 332All creates are done in the mounted file system. 333.El 334.Pp 335Any additional options specific to a file system type that is not 336one of the internally known types (see the 337.Fl t 338option) may be passed as a comma separated list; these options are 339distinguished by a leading 340.Dq \&- 341(dash). 342Options that take a value are specified using the syntax -option=value. 343For example, the 344.Nm 345command: 346.Bd -literal -offset indent 347mount -t cd9660 -o -e /dev/cd0 /cdrom 348.Ed 349.Pp 350causes 351.Nm 352to execute the equivalent of: 353.Bd -literal -offset indent 354/sbin/mount_cd9660 -e /dev/cd0 /cdrom 355.Ed 356.Pp 357Additional options specific to file system types 358which are not internally known 359(see the description of the 360.Fl t 361option below) 362may be described in the manual pages for the associated 363.Pa /sbin/mount_ Ns Sy XXX 364utilities. 365.It Fl p 366Print mount information in 367.Xr fstab 5 368format. 369Implies also the 370.Fl v 371option. 372.It Fl r 373The file system is to be mounted read-only. 374Mount the file system read-only (even the super-user may not write it). 375The same as the 376.Cm ro 377argument to the 378.Fl o 379option. 380.It Fl t Cm ufs | Ar external_type 381The argument following the 382.Fl t 383is used to indicate the file system type. 384The type 385.Cm ufs 386is the default. 387The 388.Fl t 389option can be used 390to indicate that the actions should only be taken on 391file systems of the specified type. 392More than one type may be specified in a comma separated list. 393The list of file system types can be prefixed with 394.Dq Li no 395to specify the file system types for which action should 396.Em not 397be taken. 398For example, the 399.Nm 400command: 401.Bd -literal -offset indent 402mount -a -t nonfs,nullfs 403.Ed 404.Pp 405mounts all file systems except those of type 406.Tn NFS 407and 408.Tn NULLFS . 409.Pp 410The default behavior of 411.Nm 412is to pass the 413.Fl t 414option directly to the 415.Xr nmount 2 416system call in the 417.Li fstype 418option. 419.Pp 420However, for the following file system types: 421.Cm cd9660 , 422.Cm mfs , 423.Cm msdosfs , 424.Cm nfs , 425.Cm nfs4 , 426.Cm ntfs , 427.Cm nwfs , 428.Cm nullfs , 429.Cm portalfs , 430.Cm smbfs , 431.Cm udf , 432and 433.Cm unionfs , 434.Nm 435will not call 436.Xr nmount 2 437directly and will instead attempt to execute a program in 438.Pa /sbin/mount_ Ns Sy XXX 439where 440.Sy XXX 441is replaced by the file system type name. 442For example, nfs file systems are mounted by the program 443.Pa /sbin/mount_nfs . 444.Pp 445Most file systems will be dynamically loaded by the kernel 446if not already present, and if the kernel module is available. 447.It Fl u 448The 449.Fl u 450flag indicates that the status of an already mounted file 451system should be changed. 452Any of the options discussed above (the 453.Fl o 454option) 455may be changed; 456also a file system can be changed from read-only to read-write 457or vice versa. 458An attempt to change from read-write to read-only will fail if any 459files on the file system are currently open for writing unless the 460.Fl f 461flag is also specified. 462The set of options is determined by applying the options specified 463in the argument to 464.Fl o 465and finally applying the 466.Fl r 467or 468.Fl w 469option. 470.It Fl v 471Verbose mode. 472If the 473.Fl v 474is used alone, show all file systems, including those that were mounted with the 475.Dv MNT_IGNORE 476flag and show additional information about each file system (including fsid 477when run by root). 478.It Fl w 479The file system object is to be read and write. 480.El 481.Sh ENVIRONMENT 482.Bl -tag -width ".Ev PATH_FSTAB" 483.It Ev PATH_FSTAB 484If the environment variable 485.Ev PATH_FSTAB 486is set, all operations are performed against the specified file. 487.Ev PATH_FSTAB 488will not be honored if the process environment or memory address space is 489considered 490.Dq tainted . 491(See 492.Xr issetugid 2 493for more information.) 494.El 495.Sh FILES 496.Bl -tag -width /etc/fstab -compact 497.It Pa /etc/fstab 498file system table 499.El 500.Sh DIAGNOSTICS 501Various, most of them are self-explanatory. 502.Pp 503.Dl XXXXX file system is not available 504.Pp 505The kernel does not support the respective file system type. 506Note that 507support for a particular file system might be provided either on a static 508(kernel compile-time), or dynamic basis (loaded as a kernel module by 509.Xr kldload 8 ) . 510.Sh SEE ALSO 511.Xr getfacl 1 , 512.Xr setfacl 1 , 513.Xr nmount 2 , 514.Xr acl 3 , 515.Xr mac 4 , 516.Xr ext2fs 5 , 517.Xr fstab 5 , 518.Xr procfs 5 , 519.Xr kldload 8 , 520.Xr mount_cd9660 8 , 521.Xr mount_msdosfs 8 , 522.Xr mount_nfs 8 , 523.Xr mount_ntfs 8 , 524.Xr mount_nullfs 8 , 525.Xr mount_nwfs 8 , 526.Xr mount_portalfs 8 , 527.Xr mount_smbfs 8 , 528.Xr mount_udf 8 , 529.Xr mount_unionfs 8 , 530.Xr umount 8 , 531.Xr zfs 8 , 532.Xr zpool 8 533.Sh CAVEATS 534After a successful 535.Nm , 536the permissions on the original mount point determine if 537.Pa ..\& 538is accessible from the mounted file system. 539The minimum permissions for 540the mount point for traversal across the mount point in both 541directions to be possible for all users is 0111 (execute for all). 542.Pp 543Use of the 544.Nm 545is preferred over the use of the file system specific 546.Pa mount_ Ns Sy XXX 547commands. 548In particular, 549.Xr mountd 8 550gets a 551.Dv SIGHUP 552signal (that causes an update of the export list) 553only when the file system is mounted via 554.Nm . 555.Sh HISTORY 556A 557.Nm 558utility appeared in 559.At v1 . 560.Sh BUGS 561It is possible for a corrupted file system to cause a crash. 562