diff options
Diffstat (limited to 'lib/libc/sys/mount.2')
| -rw-r--r-- | lib/libc/sys/mount.2 | 383 |
1 files changed, 383 insertions, 0 deletions
diff --git a/lib/libc/sys/mount.2 b/lib/libc/sys/mount.2 new file mode 100644 index 0000000..57ad428 --- /dev/null +++ b/lib/libc/sys/mount.2 @@ -0,0 +1,383 @@ +.\" Copyright (c) 1980, 1989, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)mount.2 8.3 (Berkeley) 5/24/95 +.\" $FreeBSD$ +.\" +.Dd January 26, 2010 +.Dt MOUNT 2 +.Os +.Sh NAME +.Nm mount , +.Nm nmount , +.Nm unmount +.Nd mount or dismount a file system +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/param.h +.In sys/mount.h +.Ft int +.Fn mount "const char *type" "const char *dir" "int flags" "void *data" +.Ft int +.Fn unmount "const char *dir" "int flags" +.In sys/uio.h +.Ft int +.Fn nmount "struct iovec *iov" "u_int niov" "int flags" +.Sh DESCRIPTION +The +.Fn mount +system call grafts +a file system object onto the system file tree +at the point +.Fa dir . +The argument +.Fa data +describes the file system object to be mounted. +The argument +.Fa type +tells the kernel how to interpret +.Fa data +(See +.Fa type +below). +The contents of the file system +become available through the new mount point +.Fa dir . +Any files in +.Fa dir +at the time +of a successful mount are swept under the carpet so to speak, and +are unavailable until the file system is unmounted. +.Pp +The +.Fn nmount +system call behaves similarly to +.Fn mount , +except that the mount options (file system type name, device to mount, +mount-point name, etc.) are passed as an array of name-value pairs +in the array +.Fa iov , +containing +.Fa niov +elements. +The following options are required by all file systems: +.Bl -item -offset indent -compact +.It +.Li fstype Ta file system type name (e.g., Dq Li procfs ) +.It +.Li fspath Ta mount point pathname (e.g., Dq Li /proc ) +.El +.Pp +Depending on the file system type, other options may be +recognized or required; +for example, most disk-based file systems require a +.Dq Li from +option containing the pathname of a special device +in addition to the options listed above. +.Pp +By default only the super-user may call the +.Fn mount +system call. +This restriction can be removed by setting the +.Va vfs.usermount +.Xr sysctl 8 +variable +to a non-zero value; see the BUGS section for more information. +.Pp +The following +.Fa flags +may be specified to +suppress default semantics which affect file system access. +.Bl -tag -width MNT_SYNCHRONOUS +.It Dv MNT_RDONLY +The file system should be treated as read-only; +even the super-user may not write on it. +Specifying MNT_UPDATE without this option will upgrade +a read-only file system to read/write. +.It Dv MNT_NOEXEC +Do not allow files to be executed from the file system. +.It Dv MNT_NOSUID +Do not honor setuid or setgid bits on files when executing them. +This flag is set automatically when the caller is not the super-user. +.It Dv MNT_NOATIME +Disable update of file access times. +.It Dv MNT_SNAPSHOT +Create a snapshot of the file system. +This is currently only supported on UFS2 file systems, see +.Xr mksnap_ffs 8 +for more information. +.It Dv MNT_SUIDDIR +Directories with the SUID bit set chown new files to their own owner. +This flag requires the SUIDDIR option to have been compiled into the kernel +to have any effect. +See the +.Xr mount 8 +and +.Xr chmod 2 +pages for more information. +.It Dv MNT_SYNCHRONOUS +All I/O to the file system should be done synchronously. +.It Dv MNT_ASYNC +All I/O to the file system should be done asynchronously. +.It Dv MNT_FORCE +Force a read-write mount even if the file system appears to be unclean. +Dangerous. +Together with +.Dv MNT_UPDATE +and +.Dv MNT_RDONLY , +specify that the file system is to be forcibly downgraded to a read-only +mount even if some files are open for writing. +.It Dv MNT_NOCLUSTERR +Disable read clustering. +.It Dv MNT_NOCLUSTERW +Disable write clustering. +.El +.Pp +The flag +.Dv MNT_UPDATE +indicates that the mount command is being applied +to an already mounted file system. +This allows the mount flags to be changed without requiring +that the file system be unmounted and remounted. +Some file systems may not allow all flags to be changed. +For example, +many file systems will not allow a change from read-write to read-only. +.Pp +The flag +.Dv MNT_RELOAD +causes the vfs subsystem to update its data structures pertaining to +the specified already mounted file system. +.Pp +The +.Fa type +argument names the file system. +The types of file systems known to the system can be obtained with +.Xr lsvfs 1 . +.Pp +The +.Fa data +argument +is a pointer to a structure that contains the type +specific arguments to mount. +The format for these argument structures is described in the +manual page for each file system. +By convention file system manual pages are named +by prefixing ``mount_'' to the name of the file system as returned by +.Xr lsvfs 1 . +Thus the +.Tn NFS +file system is described by the +.Xr mount_nfs 8 +manual page. +It should be noted that a manual page for default +file systems, known as UFS and UFS2, does not exist. +.Pp +The +.Fn unmount +system call disassociates the file system from the specified +mount point +.Fa dir . +.Pp +The +.Fa flags +argument may include +.Dv MNT_FORCE +to specify that the file system should be forcibly unmounted +even if files are still active. +Active special devices continue to work, +but any further accesses to any other active files result in errors +even if the file system is later remounted. +.Pp +If the +.Dv MNT_BYFSID +flag is specified, +.Fa dir +should instead be a file system ID encoded as +.Dq Li FSID : Ns Ar val0 : Ns Ar val1 , +where +.Ar val0 +and +.Ar val1 +are the contents of the +.Vt fsid_t +.Va val[] +array in decimal. +The file system that has the specified file system ID will be unmounted. +.Sh RETURN VALUES +.Rv -std +.Sh ERRORS +The +.Fn mount +and +.Fn nmount +system calls will fail when one of the following occurs: +.Bl -tag -width Er +.It Bq Er EPERM +The caller is neither the super-user nor the owner of +.Fa dir . +.It Bq Er ENAMETOOLONG +A component of a pathname exceeded 255 characters, +or the entire length of a path name exceeded 1023 characters. +.It Bq Er ELOOP +Too many symbolic links were encountered in translating a pathname. +.It Bq Er ENOENT +A component of +.Fa dir +does not exist. +.It Bq Er ENOTDIR +A component of +.Fa name +is not a directory, +or a path prefix of +.Fa special +is not a directory. +.It Bq Er EBUSY +Another process currently holds a reference to +.Fa dir . +.It Bq Er EFAULT +The +.Fa dir +argument +points outside the process's allocated address space. +.El +.Pp +The following errors can occur for a +.Em ufs +file system mount: +.Bl -tag -width Er +.It Bq Er ENODEV +A component of ufs_args +.Fa fspec +does not exist. +.It Bq Er ENOTBLK +The +.Fa fspec +argument +is not a block device. +.It Bq Er ENXIO +The major device number of +.Fa fspec +is out of range (this indicates no device driver exists +for the associated hardware). +.It Bq Er EBUSY +.Fa fspec +is already mounted. +.It Bq Er EMFILE +No space remains in the mount table. +.It Bq Er EINVAL +The super block for the file system had a bad magic +number or an out of range block size. +.It Bq Er ENOMEM +Not enough memory was available to read the cylinder +group information for the file system. +.It Bq Er EIO +An I/O error occurred while reading the super block or +cylinder group information. +.It Bq Er EFAULT +The +.Fa fspec +argument +points outside the process's allocated address space. +.El +.Pp +The following errors can occur for a +.Em nfs +file system mount: +.Bl -tag -width Er +.It Bq Er ETIMEDOUT +.Em Nfs +timed out trying to contact the server. +.It Bq Er EFAULT +Some part of the information described by nfs_args +points outside the process's allocated address space. +.El +.Pp +The +.Fn unmount +system call may fail with one of the following errors: +.Bl -tag -width Er +.It Bq Er EPERM +The caller is neither the super-user nor the user who issued the corresponding +.Fn mount +call. +.It Bq Er ENAMETOOLONG +The length of the path name exceeded 1023 characters. +.It Bq Er EINVAL +The requested directory is not in the mount table. +.It Bq Er ENOENT +The file system ID specified using +.Dv MNT_BYFSID +was not found in the mount table. +.It Bq Er EINVAL +The file system ID specified using +.Dv MNT_BYFSID +could not be decoded. +.It Bq Er EINVAL +The specified file system is the root file system. +.It Bq Er EBUSY +A process is holding a reference to a file located +on the file system. +.It Bq Er EIO +An I/O error occurred while writing cached file system information. +.It Bq Er EFAULT +The +.Fa dir +argument +points outside the process's allocated address space. +.El +.Pp +A +.Em ufs +mount can also fail if the maximum number of file systems are currently +mounted. +.Sh SEE ALSO +.Xr lsvfs 1 , +.Xr mksnap_ffs 8 , +.Xr mount 8 , +.Xr umount 8 +.Sh HISTORY +The +.Fn mount +and +.Fn unmount +functions appeared in +.At v6 . +The +.Fn nmount +system call first appeared in +.Fx 5.0 . +.Sh BUGS +Some of the error codes need translation to more obvious messages. +.Pp +Allowing untrusted users to mount arbitrary media, e.g. by enabling +.Va vfs.usermount , +should not be considered safe. +Most file systems in +.Fx +were not built to safeguard against malicious devices. |
