MTIO(7)                                                   MTIO(7)



     NAME
          mtio - magnetic tape interface

     DESCRIPTION
          The special file /dev/rmt1 refers to the streaming quarter
          inch cartridge magtape drive.  The special file /dev/rmt1,
          is a 10000 fci, 45 to 60 MByte quarter inch tape streaming
          drive.  The special file /dev/rmt2, is the no rewind version
          of the device.  The special file /dev/rmt3, is a 1600/6250
          bpi half-inch tape drive, and the special file /dev/rmt4, is
          the no rewind version of the half-inch tape device.
          The device /dev/bsrmt[34] for the half-inch tape does a byte
          swap upon writing and reading of the tape. This is
          particulary useful for VAX type tapes which are byteswapped
          when created.

          Refer to mt(1) for the specifications of ioctl commands to
          manipulate the tape drives.  The special files /dev/rmt1 and
          /dev/rmt3 are closed by writing a file mark and rewinding
          when writing to the tape.  The files /dev/rmt2 and /dev/rmt4
          are not rewound when closed.

          The standard quarter inch tape consists of a series of 512
          byte records terminated by an end-of-file.  The system makes
          it possible to treat the tape like any other file.  Seeks do
          not have their usual meaning and it is not possible to read
          or write a byte at a time.  Writing in very small blocks
          (less than 5120 bytes) is inadvisable because this tends to
          create large record gaps and causes the tape to stop
          streaming.

          The half-inch tape drive is written in block sizes of up to
          32 KBytes blocks.  The half-inch tape drive is a standard
          start stop device.

          The mt manipulation program discussed above is useful when
          it is desired to access the tape in a way compatible with
          ordinary files.  When foreign tapes are to be dealt with,
          and especially when long records are to be read or written,
          the `raw' interface is appropriate.  The associated files
          are named /dev/rmt1 and /dev/rmt3. A number of ioctl
          operations are available on raw magnetic tape.  Refer to
          mt(1) for additional information for use with /dev/rmt1 and
          /dev/rmt3.

          The following definitions are from /usr/include/sys/mtio.h :

          /*
           * Structures and definitions for mag tape io control commands
           */

          /* structure for MTIOCTOP - mag tape op command */

          struct    mtop      {



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     MTIO(7)                                                   MTIO(7)



                    short     mt_op;/* operations defined below */
                    daddr_t   mt_count;/* how many of them */
          };

          /* operations */

          #define   MTWEOF    0    /* write an end-of-file record */

          #define   MTFSF     1    /* forward space file */

          #define   MTBSF     2    /* backward space file */

          #define   MTFSR     3    /* forward space record */

          #define   MTBSR     4    /* backward space record */

          #define   MTREW     5    /* rewind */

          #define   MTOFFL    6    /* off-line */

          #define   MTNOP     7    /* no operation, sets status only */

          #define   MTRET     8    /* retension the tape */

          #define   MTRST     9    /* reset operation */

          /* structure for MTIOCGET - mag tape get status command */

          struct    mtget     {

                    short     mt_type;/* type of magtape device */


          /* the following two registers are very device dependent */

                    short     mt_dsreg;  /* 'drive status' register */

                    short     mt_erreg;  /* 'error' register        */

          /* end device-dependent registers */

                    short     mt_resid;  /* residual count  */

          /* the following two are not yet implemented */

                    daddr_t   mt_fileno; /*file number of current position*/

                    daddr_t   mt_blkno;  /*block number of current position*/

          /* end not yet implemented  */

          };


          Status and Error register definitions can be found in
          /usr/include/sys/tsreg.h.  Definitions are consistent among all
          quarter inch cartridge magtape drives.

          /*

           * Constants for mt_type byte

           */

          #define MT_ISQIC    0x01 /* qic-02 tape controller */

          #define MT_ISXM          0x08/* Xylogics magtape */

          #define MT_ISCPHR   0x09 /* Cipher 540S tape drive */

          /* mag tape io control commands */
          #define MTIOCODE(x) ('t'<<8|(x))
          #define   MTIOCTOP  MTIOCODE('a')/* perform tape op */
          #define   MTIOCGET  MTIOCODE('b')/* get tape status */
          #define MTIOCGETBLKSIZE MTIOCODE('c')/* get tape block size */


          Each read or write call uses the next record on the tape.


     FILES

          /dev/rmt1   Cartridge tape

          /dev/rmt2   Cartridge tape - no rewind



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     MTIO(7)                                                   MTIO(7)



          /dev/rmt3   Half-Inch tape
          /dev/rmt4   Half-Inch tape - no rewind
          /dev/bsrmt3 Half-Inch tape with byte-swap option
          /dev/bsrmt4 Half-Inch tape - no rewind with byte-swap option

          The minor device numbers for each of the above devices to
          build special files using mknod(1) is based on the standard
          default minor device number being 0x00.  The minor device
          number for the /dev/rmt2 and /dev/rmt4 is 0x01.

     SEE ALSO
          mt(1), tar(1), cpio(1)

     ORIGIN
          4.3 BSD








































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