bsd/man/man2/mount.2

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  35 .\"     @(#)mount.2     8.2 (Berkeley) 12/11/93
  36 .\"
  37 .Dd December 11, 1993
  38 .Dt MOUNT 2
  39 .Os BSD 4
  40 .Sh NAME
  41 .Nm mount ,
  42 .Nm unmount
  43 .Nd mount or dismount a filesystem
  44 .Sh SYNOPSIS
  45 .Fd #include <sys/param.h>
  46 .Fd #include <sys/mount.h>
  47 .Ft int
  48 .Fn mount "const char *type" "const char *dir" "int flags" "void *data"
  49 .Ft int
  50 .Fn unmount "const char *dir" "int flags"
  51 .Sh DESCRIPTION
  52 The
  53 .Fn mount
  54 function grafts
  55 a filesystem object onto the system file tree
  56 at the point
  57 .Ar dir .
  58 The argument
  59 .Ar data
  60 describes the filesystem object to be mounted.
  61 The argument
  62 .Ar type
  63 tells the kernel how to interpret
  64 .Ar data
  65 (See
  66 .Ar type
  67 below).
  68 The contents of the filesystem
  69 become available through the new mount point
  70 .Ar dir .
  71 Any files in
  72 .Ar dir
  73 at the time
  74 of a successful mount are swept under the carpet so to speak, and
  75 are unavailable until the filesystem is unmounted.
  76 .Pp
  77 The following
  78 .Ar flags
  79 may be specified to
  80 suppress default semantics which affect filesystem access.
  81 .Bl -tag -width MNT_SYNCHRONOUS
  82 .It Dv MNT_RDONLY
  83 The filesystem should be treated as read-only;
  84 Even the super-user may not write on it.
  85 .It Dv MNT_NOEXEC
  86 Do not allow files to be executed from the filesystem.
  87 .It Dv MNT_NOSUID
  88 Do not honor setuid or setgid bits on files when executing them.
  89 .It Dv MNT_NODEV
  90 Do not interpret special files on the filesystem.
  91 .It Dv MNT_UNION
  92 Union with underlying filesystem instead of obscuring it.
  93 .It Dv MNT_SYNCHRONOUS
  94 All I/O to the filesystem should be done synchronously.
  95 .El
  96 .Pp
  97 The flag
  98 .Dv MNT_UPDATE
  99 indicates that the mount command is being applied
 100 to an already mounted filesystem.
 101 This allows the mount flags to be changed without requiring
 102 that the filesystem be unmounted and remounted.
 103 Some filesystems may not allow all flags to be changed.
 104 For example,
 105 most filesystems will not allow a change from read-write to read-only.
 106 .Pp
 107 The flag
 108 .Dv MNT_RELOAD
 109 causes the vfs subsystem to update its data structures pertaining to
 110 the specified already mounted filesystem.
 111 .Pp
 112 The
 113 .Fa type
 114 argument defines the type of the filesystem.
 115 .Pp
 116 .Fa Data
 117 is a pointer to a structure that contains the type
 118 specific arguments to mount.
 119 The format for these argument structures is described in the
 120 manual page for each filesystem.
 121 .Pp
 122 The
 123 .Fn umount
 124 function call disassociates the filesystem from the specified
 125 mount point
 126 .Fa dir .
 127 .Pp
 128 The
 129 .Fa flags
 130 argument may specify
 131 .Dv MNT_FORCE
 132 to specify that the filesystem should be forcibly unmounted even if files are
 133 still active.
 134 Active special devices continue to work,
 135 but any further accesses to any other active files result in errors
 136 even if the filesystem is later remounted.
 137 .Sh RETURN VALUES
 138 The
 139 .Fn mount
 140 returns the value 0 if the mount was successful, otherwise -1 is returned
 141 and the variable
 142 .Va errno
 143 is set to indicate the error.
 144 .Pp
 145 .Nm Umount
 146 returns the value 0 if the umount succeeded; otherwise -1 is returned
 147 and the variable
 148 .Va errno
 149 is set to indicate the error.
 150 .Sh ERRORS
 151 .Fn Mount
 152 will fail when one of the following occurs:
 153 .Bl -tag -width [ENAMETOOLONG]
 154 .It Bq Er EPERM
 155 The caller is not the super-user, and the device-node and the mountpoint
 156 do not have adequate ownership and permissions.
 157 .It Bq Er ENAMETOOLONG
 158 A component of a pathname exceeded
 159 .Dv {NAME_MAX}
 160 characters, or an entire path name exceeded
 161 .Dv {PATH_MAX}
 162 characters.
 163 .It Bq Er ELOOP
 164 Too many symbolic links were encountered in translating a pathname.
 165 .It Bq Er ENOENT
 166 A component of
 167 .Fa dir
 168 does not exist.
 169 .It Bq Er ENOTDIR
 170 A component of
 171 .Ar name
 172 is not a directory,
 173 or a path prefix of
 174 .Ar special
 175 is not a directory.
 176 .It Bq Er EINVAL
 177 A pathname contains a character with the high-order bit set.
 178 .It Bq Er EBUSY
 179 Another process currently holds a reference to
 180 .Fa dir .
 181 .It Bq Er EFAULT
 182 .Fa Dir
 183 points outside the process's allocated address space.
 184 .El
 185 .Pp
 186 .Nm Umount
 187 may fail with one of the following errors:
 188 .Bl -tag -width [ENAMETOOLONG]
 189 .It Bq Er EPERM
 190 The caller is not the super-user, and the
 191 .Nm mount()
 192 was not done by the user.
 193 .It Bq Er ENOTDIR
 194 A component of the path is not a directory.
 195 .It Bq Er EINVAL
 196 The pathname contains a character with the high-order bit set.
 197 .It Bq Er ENAMETOOLONG
 198 A component of a pathname exceeded
 199 .Dv {NAME_MAX}
 200 characters, or an entire path name exceeded
 201 .Dv {PATH_MAX}
 202 characters.
 203 .It Bq Er ELOOP
 204 Too many symbolic links were encountered in translating the pathname.
 205 .It Bq Er EINVAL
 206 The requested directory is not in the mount table.
 207 .It Bq Er EBUSY
 208 A process is holding a reference to a file located
 209 on the filesystem.
 210 .It Bq Er EIO
 211 An I/O error occurred while writing cached filesystem information.
 212 .It Bq Er EFAULT
 213 .Fa Dir
 214 points outside the process's allocated address space.
 215 .El
 216 .Sh SEE ALSO
 217 .Xr mount 8 ,
 218 .Xr umount 8
 219 .Sh BUGS
 220 Some of the error codes need translation to more obvious messages.
 221 .Sh HISTORY
 222 .Fn Mount
 223 and
 224 .Fn umount
 225 function calls appeared in
 226 .At v6 .