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 .It Dv MNT_CPROTECT
  96 Enable data protection on the filesystem if the filesystem is configured for it.
  97 .El
  98 .Pp
  99 The flag
 100 .Dv MNT_UPDATE
 101 indicates that the mount command is being applied
 102 to an already mounted filesystem.
 103 This allows the mount flags to be changed without requiring
 104 that the filesystem be unmounted and remounted.
 105 Some filesystems may not allow all flags to be changed.
 106 For example,
 107 most filesystems will not allow a change from read-write to read-only.
 108 .Pp
 109 The flag
 110 .Dv MNT_RELOAD
 111 causes the vfs subsystem to update its data structures pertaining to
 112 the specified already mounted filesystem.
 113 .Pp
 114 The
 115 .Fa type
 116 argument defines the type of the filesystem.
 117 .Pp
 118 .Fa Data
 119 is a pointer to a structure that contains the type
 120 specific arguments to mount.
 121 The format for these argument structures is described in the
 122 manual page for each filesystem.
 123 .Pp
 124 The
 125 .Fn unmount
 126 function call disassociates the filesystem from the specified
 127 mount point
 128 .Fa dir .
 129 .Pp
 130 The
 131 .Fa flags
 132 argument may specify
 133 .Dv MNT_FORCE
 134 to specify that the filesystem should be forcibly unmounted even if files are
 135 still active.
 136 Active special devices continue to work,
 137 but any further accesses to any other active files result in errors
 138 even if the filesystem is later remounted.
 139 .Sh RETURN VALUES
 140 The
 141 .Fn mount
 142 returns the value 0 if the mount was successful, otherwise -1 is returned
 143 and the variable
 144 .Va errno
 145 is set to indicate the error.
 146 .Pp
 147 .Nm unmount
 148 returns the value 0 if the unmount succeeded; otherwise -1 is returned
 149 and the variable
 150 .Va errno
 151 is set to indicate the error.
 152 .Sh ERRORS
 153 .Fn Mount
 154 will fail when one of the following occurs:
 155 .Bl -tag -width [ENAMETOOLONG]
 156 .It Bq Er EPERM
 157 The caller is not the super-user, and the device-node and the mountpoint
 158 do not have adequate ownership and permissions.
 159 .It Bq Er ENAMETOOLONG
 160 A component of a pathname exceeded
 161 .Dv {NAME_MAX}
 162 characters, or an entire path name exceeded
 163 .Dv {PATH_MAX}
 164 characters.
 165 .It Bq Er ELOOP
 166 Too many symbolic links were encountered in translating a pathname.
 167 .It Bq Er ENOENT
 168 A component of
 169 .Fa dir
 170 does not exist.
 171 .It Bq Er ENOTDIR
 172 A component of
 173 .Ar name
 174 is not a directory,
 175 or a path prefix of
 176 .Ar special
 177 is not a directory.
 178 .It Bq Er EINVAL
 179 A pathname contains a character with the high-order bit set.
 180 .It Bq Er EBUSY
 181 Another process currently holds a reference to
 182 .Fa dir .
 183 .It Bq Er EFAULT
 184 .Fa Dir
 185 points outside the process's allocated address space.
 186 .El
 187 .Pp
 188 .Nm unmount
 189 may fail with one of the following errors:
 190 .Bl -tag -width [ENAMETOOLONG]
 191 .It Bq Er EPERM
 192 The caller is not the super-user, and the
 193 .Nm mount()
 194 was not done by the user.
 195 .It Bq Er ENOTDIR
 196 A component of the path is not a directory.
 197 .It Bq Er EINVAL
 198 The pathname contains a character with the high-order bit set.
 199 .It Bq Er ENAMETOOLONG
 200 A component of a pathname exceeded
 201 .Dv {NAME_MAX}
 202 characters, or an entire path name exceeded
 203 .Dv {PATH_MAX}
 204 characters.
 205 .It Bq Er ELOOP
 206 Too many symbolic links were encountered in translating the pathname.
 207 .It Bq Er EINVAL
 208 The requested directory is not in the mount table.
 209 .It Bq Er EBUSY
 210 A process is holding a reference to a file located
 211 on the filesystem.
 212 .It Bq Er EIO
 213 An I/O error occurred while writing cached filesystem information.
 214 .It Bq Er EFAULT
 215 .Fa Dir
 216 points outside the process's allocated address space.
 217 .El
 218 .Sh SEE ALSO
 219 .Xr mount 8 ,
 220 .Xr unmount 8
 221 .Sh BUGS
 222 Some of the error codes need translation to more obvious messages.
 223 .Sh HISTORY
 224 .Fn Mount
 225 and
 226 .Fn unmount
 227 function calls appeared in
 228 .At v6 .