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OpenSolaris 2009.06 - man page for mnttab (opensolaris section 4)

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mnttab(4)				   File Formats 				mnttab(4)

       mnttab - mounted file system table

       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 getmntent(3C). Mounting a file system adds an entry to this table.
       Unmounting removes an entry from this table. Remounting a file system causes the  informa-
       tion  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  system  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 regular  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


       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).

       The following ioctl(2) calls are supported:

       MNTIOC_NMNTS	    Returns the count of mounted resources in the current 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  number  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 sys-
			    tem 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 structure 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.

       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 memory 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

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

       /etc/mnttab		   Usual mount point for mnttab file system

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

       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)

       The  mnttab  file system provides the previously undocumented dev=xxx option in the option
       string for each mounted file system. This is provided for legacy applications  that  might
       have been using the dev=information option.

       Using  dev=option in applications is strongly discouraged. The device number string repre-
       sents a 32-bit quantity and might not contain correct information in 64-bit environments.

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

       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 modification 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.

SunOS 5.11				   20 Dec 2003					mnttab(4)
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