mnttab man page on SmartOS

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MNTTAB(4)							     MNTTAB(4)

NAME
       mnttab - mounted file system table

DESCRIPTION
       The  file  /etc/mnttab  is really a file system that provides read-only
       access to the table of mounted  file  systems  for  the	current	 host.
       /etc/mnttab  is read by programs using the routines described in getmn‐
       tent(3C). Mounting a file system adds an entry to this table.  Unmount‐
       ing  removes  an entry from this table. Remounting a file system causes
       the information in the mounted file  system  table  to  be  updated  to
       reflect	any  changes  caused by the remount. The list is maintained by
       the kernel in order of mount time. That is, the first mounted file sys‐
       tem  is	first in the list and the most recently mounted file system is
       last. When mounted on a mount point the file system appears as a	 regu‐
       lar file containing the current mnttab information.

       Each entry is a line of fields separated by TABs in the form:

	 special   mount_point	 fstype	  options   time

       where:

       special
		      The name of the resource that has been mounted.

       mount_point
		      The pathname of the directory on which the filesystem is
		      mounted.

       fstype
		      The file system type of the mounted file system.

       options
		      The mount options. See respective mount file system  man
		      page in the See Also section below.

       time
		      The time at which the file system was mounted.

       Examples	 of  entries  for  the special field include the pathname of a
       block-special device, the name of a remote file system in the  form  of
       host:pathname,  or  the	name  of a swap file, for example, a file made
       with mkfile(1M).

IOCTLS
       The following ioctl(2) calls are supported:

       MNTIOC_NMNTS
			    Returns the count of mounted resources in the cur‐
			    rent snapshot in the uint32_t pointed to by arg.

       MNTIOC_GETDEVLIST
			    Returns  an	 array	of uint32_t's that is twice as
			    long as the length returned by MNTIOC_NMNTS.  Each
			    pair of numbers is the major and minor device num‐
			    ber for the file system at the corresponding  line
			    in the current /etc/mnttab snapshot. arg points to
			    the memory buffer to  receive  the	device	number
			    information.

       MNTIOC_SETTAG
			    Sets  a  tag  word	into  the  options  list for a
			    mounted file system. A tag is a notation that will
			    appear  in	the  options  string of a mounted file
			    system but it is not recognized or interpreted  by
			    the	 file  system  code. arg points to a filled in
			    mnttagdesc structure, as shown  in	the  following
			    example:

			      uint_t  mtd_major;  /* major number for mounted fs */
			      uint_t  mtd_minor;  /* minor number for mounted fs */
			      char    *mtd_mntpt; /* mount point of file system */
			      char    *mtd_tag;	  /* tag to set/clear */

			    If the tag already exists then it is marked as set
			    but	 not   re-added.   Tags	  can	be   at	  most
			    MAX_MNTOPT_TAG long.

			    Use	 of this ioctl is restricted to processes with
			    the {PRIV_SYS_MOUNT} privilege.

       MNTIOC_CLRTAG
			    Marks a tag in the options list for a mounted file
			    system  as	not set. arg points to the same struc‐
			    ture as MNTIOC_SETTAG, which identifies  the  file
			    system and tag to be cleared.

			    Use	 of this ioctl is restricted to processes with
			    the {PRIV_SYS_MOUNT} privilege.

ERRORS
       EFAULT
		       The arg pointer in an MNTIOC_ ioctl call pointed to  an
		       inaccessible  memory location or a character pointer in
		       a mnttagdesc structure pointed to an inaccessible  mem‐
		       ory location.

       EINVAL
		       The  tag	 specified  in	a  MNTIOC_SETTAG  call already
		       exists as a file system option, or the tag specified in
		       a MNTIOC_CLRTAG call does not exist.

       ENAMETOOLONG
		       The  tag	 specified in a MNTIOC_SETTAG call is too long
		       or the tag would make the total length  of  the	option
		       string for the mounted file system too long.

       EPERM
		       The  calling  process  does  not	 have {PRIV_SYS_MOUNT}
		       privilege and either a MNTIOC_SETTAG  or	 MNTIOC_CLRTAG
		       call was made.

FILES
       /etc/mnttab
				   Usual mount point for mnttab file system

       /usr/include/sys/mntio.h
				   Header file that contains IOCTL definitions

SEE ALSO
       mkfile(1M),     mount_cachefs(1M),    mount_hsfs(1M),	mount_nfs(1M),
       mount_pcfs(1M), mount_ufs(1M), mount(1M), ioctl(2),  read(2),  poll(2),
       stat(2), getmntent(3C)

WARNINGS
       The  mnttab  file  system  provides the previously undocumented dev=xxx
       option in the option string for each mounted file system.  This is pro‐
       vided for legacy applications that might have been using the dev=infor‐
       mation option.

       Using dev=option in applications is strongly  discouraged.  The	device
       number  string  represents a 32-bit quantity and might not contain cor‐
       rect information in 64-bit environments.

       Applications requiring device number information for mounted file  sys‐
       tems  should  use the getextmntent(3C) interface, which functions prop‐
       erly in either 32- or 64-bit environments.

NOTES
       The snapshot of the mnttab information is taken any time a  read(2)  is
       performed at offset 0 (the beginning) of the mnttab file. The file mod‐
       ification time returned by stat(2) for the mnttab file is the  time  of
       the  last  change  to mounted file system information. A poll(2) system
       call requesting a POLLRDBAND event can be used to block	and  wait  for
       the  system's  mounted file system information to be different from the
       most recent snapshot since the mnttab file was opened.

				 Dec 20, 2003			     MNTTAB(4)
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