mnttab(4)                                                          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. 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
       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 <TAB>s 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 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 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 structure as MNTIOC_SETTAG, which  identi-
           fies 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 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.

       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=information 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 systems 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
       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) sys-
       tem  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 5.10                                                          20 Dec 2003                                                          mnttab(4)