.\" $NetBSD: mount.2,v 1.50.12.1 2019/09/05 08:19:40 martin Exp $ .\" .\" 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. .\" 3. 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 .\" .Dd September 2, 2019 .Dt MOUNT 2 .Os .Sh NAME .Nm mount , .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" "size_t data_len" .Ft int .Fn unmount "const char *dir" "int flags" .Sh DESCRIPTION The .Fn mount function grafts a file system object onto the system file tree at the point .Ar dir . The argument .Ar data describes the file system object to be mounted, and is .Ar data_len bytes long. The argument .Ar type tells the kernel how to interpret .Ar data (See .Ar type below). The contents of the file system become available through the new mount point .Ar dir . Any files in .Ar 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 following .Ar 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. .It Dv MNT_UNION Union with underlying file system instead of obscuring it. .It Dv MNT_HIDDEN Cause the .Xr df 1 program, and perhaps others, to, by default, exclude this file system from its output. .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. .It Dv MNT_NODEV Do not interpret special files on the file system. .It Dv MNT_NOCOREDUMP Do not allow programs to dump core files on the file system. .It Dv MNT_NOATIME Never update access time in the file system. .It Dv MNT_RELATIME Update access time on write and change. This helps programs that verify that the file has been read after written to work. .It Dv MNT_NODEVMTIME Never update modification time of device files. .It Dv MNT_SYMPERM Recognize the permission of symbolic link when reading or traversing. .It Dv MNT_SYNCHRONOUS All I/O to the file system should be done synchronously. This will slow I/O performance considerably, but enhances overall file system reliability. .It Dv MNT_ASYNC All I/O to the file system should be done asynchronously. This vastly improves I/O throughput, but at a cost of making the file system likely to be completely unrecoverable should the system crash while unwritten data is pending in kernel buffers. .It Dv MNT_LOG Use a file system journal. .Dv MNT_LOG causes a journal (or log) to be created in the file system, creating a record of meta-data writes to be performed, allowing the actual writes to be deferred. This improves performance in most cases. .It MNT_EXTATTR Enable extended attributes, if the file system supports them and does not enable them by default. Currently this is only the case for UFS1. .El .Pp The .Dv MNT_UPDATE , .Dv MNT_RELOAD , and .Dv MNT_GETARGS flags indicate that the mount command is being applied to an already mounted file system. The .Dv MNT_UPDATE flag allows the mount flags to be changed without requiring that the file system be unmounted and remounted. A conversion from read-write to read-only will fail if any files are currently open for writing on the file system, unless the .Dv MNT_FORCE flag is also applied. Some file systems may not allow all flags to be changed. For example, some file systems will not allow a change from read-write to read-only. The .Dv MNT_RELOAD flag causes kernel file system data to be reloaded from the file system device. It is only permitted on file systems mounted read-only. Its purpose is to notify the system that the file system data has been modified by some external process. The .Dv MNT_GETARGS flag does not alter any of the mounted file system's properties, but returns the file system-specific arguments for the currently mounted file system. .Pp The .Fa type argument defines the type of the file system. The types of file systems known to the system are defined in .In sys/mount.h , and those supported by the current running kernel obtained using .Xr sysctl 8 to obtain the node .\" .Bd -literal -offset indent vfs.generic.fstypes. .\" XXX from lite-2: .\" The types of file systems known to the system can be obtained with .\" .Xr sysctl 8 .\" by using the command: .\" .Bd -literal -offset indent .\" sysctl vfs .\" .Ed .\" .Pp .Fa data is a pointer to a structure that contains the type specific arguments to mount. Some of the currently supported types of file systems and their type specific data are: .Pp .Dv MOUNT_FFS .Bd -literal -offset indent -compact struct ufs_args { char *fspec; /* block special file to mount */ }; .Ed .Pp .Dv MOUNT_NFS .Bd -literal -offset indent -compact struct nfs_args { int version; /* args structure version */ struct sockaddr *addr; /* file server address */ int addrlen; /* length of address */ int sotype; /* Socket type */ int proto; /* and Protocol */ u_char *fh; /* File handle to be mounted */ int fhsize; /* Size, in bytes, of fh */ int flags; /* flags */ int wsize; /* write size in bytes */ int rsize; /* read size in bytes */ int readdirsize; /* readdir size in bytes */ int timeo; /* initial timeout in .1 secs */ int retrans; /* times to retry send */ int maxgrouplist; /* Max. size of group list */ int readahead; /* # of blocks to readahead */ int leaseterm; /* Term (sec) of lease */ int deadthresh; /* Retrans threshold */ char *hostname; /* server's name */ }; .Ed .Pp .Dv MOUNT_MFS .Bd -literal -offset indent -compact struct mfs_args { char *fspec; /* name to export for statfs */ struct export_args30 pad; /* unused */ caddr_t base; /* base of file system in mem */ u_long size; /* size of file system */ }; .Ed .\" XXX from lite-2: .\" 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 sysctl 8 . .\" Thus the .\" .Nm NFS .\" file system is described by the .\" .Xr mount_nfs 8 .\" manual page. .Pp The .Fn unmount function call disassociates the file system from the specified mount point .Fa dir . .Pp The .Fa flags argument may specify .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. .Sh RETURN VALUES .Fn mount returns the value 0 if the mount was successful, the number of bytes written to .Ar data for .Dv MNT_GETARGS , otherwise \-1 is returned and the variable .Va errno is set to indicate the error. .Pp .Fn unmount returns the value 0 if the unmount succeeded; otherwise \-1 is returned and the variable .Va errno is set to indicate the error. .Sh ERRORS .Fn mount will fail when one of the following occurs: .Bl -tag -width Er .It Bq Er EBUSY Another process currently holds a reference to .Fa dir , or for an update from read-write to read-only there are files on the file system open for writes. .It Bq Er EFAULT .Fa dir points outside the process's allocated address space. .It Bq Er ELOOP Too many symbolic links were encountered in translating a pathname. .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Brq Dv NAME_MAX characters, or an entire path name exceeded .Brq Dv PATH_MAX characters. .It Bq Er ENOENT A component of .Fa dir does not exist. .It Bq Er ENOTDIR A component of .Ar name is not a directory, or a path prefix of .Ar special is not a directory. .It Bq Er EPERM The caller is not the super-user, and ordinary user mounts are not permitted or this particular request violates the rules. .El .Pp The following errors can occur for a .Em ufs file system mount: .Bl -tag -width Er .It Bq Er EBUSY .Ar Fspec is already mounted. .It Bq Er EFAULT .Ar Fspec points outside the process's allocated address space. .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 EIO An I/O error occurred while reading the super block or cylinder group information. .It Bq Er EMFILE No space remains in the mount table. .It Bq Er ENODEV A component of ufs_args .Ar fspec does not exist. .It Bq Er ENOMEM Not enough memory was available to read the cylinder group information for the file system. .It Bq Er ENOTBLK .Ar Fspec is not a block device. .It Bq Er ENXIO The major device number of .Ar fspec is out of range (this indicates no device driver exists for the associated hardware). .El .Pp The following errors can occur for a .Em nfs file system mount: .Bl -tag -width Er .It Bq Er EFAULT Some part of the information described by nfs_args points outside the process's allocated address space. .It Bq Er ETIMEDOUT .Em Nfs timed out trying to contact the server. .El .Pp The following errors can occur for a .Em mfs file system mount: .Bl -tag -width Er .It Bq Er EFAULT .Em Name points outside the process's allocated address space. .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 EIO A paging error occurred while reading the super block or cylinder group information. .It Bq Er EMFILE No space remains in the mount table. .It Bq Er ENOMEM Not enough memory was available to read the cylinder group information for the file system. .El .Pp .Fn unmount may fail with one of the following errors: .Bl -tag -width Er .It Bq Er EBUSY A process is holding a reference to a file located on the file system. .It Bq Er EFAULT .Fa dir points outside the process's allocated address space. .It Bq Er EINVAL The requested directory is not in the mount table. .It Bq Er EIO An I/O error occurred while writing cached file system information. .It Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Brq Dv NAME_MAX characters, or an entire path name exceeded .Brq Dv PATH_MAX characters. .It Bq Er ENOTDIR A component of the path is not a directory. .It Bq Er EPERM The caller is not the super-user. .El .Pp A .Em ufs or .Em mfs mount can also fail if the maximum number of file systems are currently mounted. .Sh SEE ALSO .Xr df 1 , .Xr getvfsstat 2 , .Xr nfssvc 2 , .Xr getmntinfo 3 , .Xr symlink 7 , .Xr mount 8 , .Xr sysctl 8 , .Xr umount 8 .Sh HISTORY The .Fn mount and .Fn umount (now .Fn unmount ) functions appeared in .At v1 . .Pp Prior to .Nx 4.0 the .Nm call was used to export NFS file systems. This is now done through .Fn nfssvc . .Pp The .Dv data_len argument was added for .Nx 5.0 . .Sh BUGS Some of the error codes need translation to more obvious messages. .Pp Far more file systems are supported than those those listed.