mnttab

 

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 File Formats                                            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 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 infor-
      mation in the mounted file system table  to  be  updated  to
      reflect any changes caused by the remount. The list is main-
      tained 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 con-
      taining the current mnttab information.
 
      Each entry is a line of fields separated by  spaces  in  the
      form:
 
           special   mount_point   fstype   options   time
 
 
      where
 
      special
            The name of the resource to be 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 SEE ALSO.)
 
      time  The time at which the file system was mounted.
 
      Examples of entries for the special field include the  path-
      name  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_NMOUNTS
            Returns the count of mounted resources in the  current
 
 
 
 SunOS 5.8           Last change: 29 Sep 1999                    1
 
 
 
 
 
 
 File Formats                                            mnttab(4)
 
 
 
            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_NMOUNTS. 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 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.
 
      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.
 
 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
            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 long.
 
 WARNINGS
      The mnttab file system provides the previously  undocumented
      dev=xxx  option  in  the option string for each mounted file
 
 
 
 SunOS 5.8           Last change: 29 Sep 1999                    2
 
 
 
 
 
 
 File Formats                                            mnttab(4)
 
 
 
      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 represents a  32-bit quantity and
      might not contain correct  information  in  64-bit  environ-
      ments.
 
      Applications requiring device number information for mounted
      file  systems  should  use  the  getextmntent(3C) interface,
      which functions properly in either 32-  or  64-bit  environ-
      ments.
 


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)
 


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 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  dif-
      ferent  from  the most recent snapshot since the mnttab file
      was opened.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 SunOS 5.8           Last change: 29 Sep 1999                    3
 
 
 

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