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_NOATIME
  86 Do not update the access time on files in the filesystem unless
  87 the modification or status change times are also being updated.
  88 .It Dv MNT_NOEXEC
  89 Do not allow files to be executed from the filesystem.
  90 .It Dv MNT_NOSUID
  91 Do not honor setuid or setgid bits on files when executing them.
  92 .It Dv MNT_NODEV
  93 Do not interpret special files on the filesystem.
  94 .It Dv MNT_UNION
  95 Union with underlying filesystem instead of obscuring it.
  96 .It Dv MNT_SYNCHRONOUS
  97 All I/O to the filesystem should be done synchronously.
  98 .El
  99 .Pp
 100 The flag
 101 .Dv MNT_UPDATE
 102 indicates that the mount command is being applied
 103 to an already mounted filesystem.
 104 This allows the mount flags to be changed without requiring
 105 that the filesystem be unmounted and remounted.
 106 Some filesystems may not allow all flags to be changed.
 107 For example,
 108 most filesystems will not allow a change from read-write to read-only.
 109 .Pp
 110 The
 111 .Fa type
 112 argument defines the type of the filesystem.
 113 The types of filesystems known to the system are defined in
 114 .Aq Pa sys/mount.h .
 115 .Fa Data
 116 is a pointer to a structure that contains the type
 117 specific arguments to mount.
 118 The currently supported types of filesystems and
 119 their type specific data are:
 120 .Pp
 121 .Dv MOUNT_FFS
 122 .Bd -literal -offset indent -compact
 123 struct ufs_args {
 124       char      *fspec;             /* block special file to mount */
 125       struct    export_args export; /* network export information */
 126 };
 127 .Ed
 128 .Pp
 129 .Dv MOUNT_NFS
 130 .Bd -literal -offset indent -compact
 131 struct nfs_args {
 132       int             version;      /* args structure version */
 133       struct sockaddr *addr;        /* file server address */
 134       int             addrlen;      /* length of address */
 135       int             sotype;       /* Socket type */
 136       int             proto;        /* and Protocol */
 137       u_char          *fh;          /* File handle to be mounted */
 138       int             fhsize;       /* Size, in bytes, of fh */
 139       int             flags;        /* flags */
 140       int             wsize;        /* write size in bytes */
 141       int             rsize;        /* read size in bytes */
 142       int             readdirsize;  /* readdir size in bytes */
 143       int             timeo;        /* initial timeout in .1 secs */
 144       int             retrans;      /* times to retry send */
 145       int             maxgrouplist; /* Max. size of group list */
 146       int             readahead;    /* # of blocks to readahead */
 147       int             leaseterm;    /* Term (sec) of lease */
 148       int             deadthresh;   /* Retrans threshold */
 149       char            *hostname;    /* server's name */
 150 };
 151 .Ed
 152 .Pp
 153 .Dv MOUNT_MFS
 154 .Bd -literal -offset indent -compact
 155 struct mfs_args {
 156       char      *fspec;             /* name to export for statfs */
 157       struct    export_args export; /* if we can export an MFS */
 158       caddr_t   base;               /* base of filesystem in mem */
 159       u_long    size;               /* size of filesystem */
 160 };
 161 .Ed
 162 .Pp
 163 The
 164 .Fn umount
 165 function call disassociates the filesystem from the specified
 166 mount point
 167 .Fa dir .
 168 .Pp
 169 The
 170 .Fa flags
 171 argument may specify
 172 .Dv MNT_FORCE
 173 to specify that the filesystem should be forcibly unmounted even if files are
 174 still active.
 175 Active special devices continue to work,
 176 but any further accesses to any other active files result in errors
 177 even if the filesystem is later remounted.
 178 .Sh RETURN VALUES
 179 The
 180 .Fn mount
 181 returns the value 0 if the mount was successful, otherwise -1 is returned
 182 and the variable
 183 .Va errno
 184 is set to indicate the error.
 185 .Pp
 186 .Nm Umount
 187 returns the value 0 if the umount succeeded; otherwise -1 is returned
 188 and the variable
 189 .Va errno
 190 is set to indicate the error.
 191 .Sh ERRORS
 192 .Fn Mount
 193 will fail when one of the following occurs:
 194 .Bl -tag -width [ENAMETOOLONG]
 195 .It Bq Er EPERM
 196 The caller is not the super-user.
 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 a pathname.
 205 .It Bq Er ENOENT
 206 A component of
 207 .Fa dir
 208 does not exist.
 209 .It Bq Er ENOTDIR
 210 A component of
 211 .Ar name
 212 is not a directory,
 213 or a path prefix of
 214 .Ar special
 215 is not a directory.
 216 .It Bq Er EINVAL
 217 A pathname contains a character with the high-order bit set.
 218 .It Bq Er EBUSY
 219 Another process currently holds a reference to
 220 .Fa dir .
 221 .It Bq Er EFAULT
 222 .Fa Dir
 223 points outside the process's allocated address space.
 224 .El
 225 .Pp
 226 The following errors can occur for a
 227 .Em ufs
 228 filesystem mount:
 229 .Bl -tag -width [ENOTBLK]
 230 .It Bq Er ENODEV
 231 A component of ufs_args
 232 .Ar fspec
 233 does not exist.
 234 .It Bq Er ENOTBLK
 235 .Ar Fspec
 236 is not a block device.
 237 .It Bq Er ENXIO
 238 The major device number of
 239 .Ar fspec
 240 is out of range (this indicates no device driver exists
 241 for the associated hardware).
 242 .It Bq Er EBUSY
 243 .Ar Fspec
 244 is already mounted.
 245 .It Bq Er EMFILE
 246 No space remains in the mount table.
 247 .It Bq Er EINVAL
 248 The super block for the filesystem had a bad magic
 249 number or an out of range block size.
 250 .It Bq Er ENOMEM
 251 Not enough memory was available to read the cylinder
 252 group information for the filesystem.
 253 .It Bq Er EIO
 254 An I/O error occurred while reading the super block or
 255 cylinder group information.
 256 .It Bq Er EFAULT
 257 .Ar Fspec
 258 points outside the process's allocated address space.
 259 .El
 260 .Pp
 261 The following errors can occur for a
 262 .Em nfs
 263 filesystem mount:
 264 .Bl -tag -width [ETIMEDOUT]
 265 .It Bq Er ETIMEDOUT
 266 .Em Nfs
 267 timed out trying to contact the server.
 268 .It Bq Er EFAULT
 269 Some part of the information described by nfs_args
 270 points outside the process's allocated address space.
 271 .El
 272 .Pp
 273 The following errors can occur for a
 274 .Em mfs
 275 filesystem mount:
 276 .Bl -tag -width [EMFILE]
 277 .It Bq Er EMFILE
 278 No space remains in the mount table.
 279 .It Bq Er EINVAL
 280 The super block for the filesystem had a bad magic
 281 number or an out of range block size.
 282 .It Bq Er ENOMEM
 283 Not enough memory was available to read the cylinder
 284 group information for the filesystem.
 285 .It Bq Er EIO
 286 A paging error occurred while reading the super block or
 287 cylinder group information.
 288 .It Bq Er EFAULT
 289 .Em Name
 290 points outside the process's allocated address space.
 291 .El
 292 .Pp
 293 .Nm Umount
 294 may fail with one of the following errors:
 295 .Bl -tag -width [ENAMETOOLONG]
 296 .It Bq Er EPERM
 297 The caller is not the super-user.
 298 .It Bq Er ENOTDIR
 299 A component of the path is not a directory.
 300 .It Bq Er EINVAL
 301 The pathname contains a character with the high-order bit set.
 302 .It Bq Er ENAMETOOLONG
 303 A component of a pathname exceeded
 304 .Dv {NAME_MAX}
 305 characters, or an entire path name exceeded
 306 .Dv {PATH_MAX}
 307 characters.
 308 .It Bq Er ELOOP
 309 Too many symbolic links were encountered in translating the pathname.
 310 .It Bq Er EINVAL
 311 The requested directory is not in the mount table.
 312 .It Bq Er EBUSY
 313 A process is holding a reference to a file located
 314 on the filesystem.
 315 .It Bq Er EIO
 316 An I/O error occurred while writing cached filesystem information.
 317 .It Bq Er EFAULT
 318 .Fa Dir
 319 points outside the process's allocated address space.
 320 .El
 321 .Pp
 322 A
 323 .Em ufs
 324 or
 325 .Em mfs
 326 mount can also fail if the maximum number of filesystems are currently
 327 mounted.
 328 .Sh SEE ALSO
 329 .Xr mount 8 ,
 330 .Xr umount 8 ,
 331 .Xr mfs 8
 332 .Sh BUGS
 333 Some of the error codes need translation to more obvious messages.
 334 .Sh HISTORY
 335 .Fn Mount
 336 and
 337 .Fn umount
 338 function calls appeared in
 339 .At v6 .