Documentation/s390/TAPE

   1 Channel attached Tape device driver
   2
   3 -----------------------------WARNING-----------------------------------------
   4 This driver is considered to be EXPERIMENTAL. Do NOT use it in
   5 production environments. Feel free to test it and report problems back to us.
   6 -----------------------------------------------------------------------------
   7
   8 The LINUX for zSeries tape device driver manages channel attached tape drives
   9 which are compatible to IBM 3480 or IBM 3490 magnetic tape subsystems. This
  10 includes various models of these devices (for example the 3490E).
  11
  12
  13 Tape driver features
  14
  15 The device driver supports a maximum of 128 tape devices.
  16 No official LINUX device major number is assigned to the zSeries tape device
  17 driver. It allocates major numbers dynamically and reports them on system
  18 startup.
  19 Typically it will get major number 254 for both the character device front-end
  20 and the block device front-end.
  21
  22 The tape device driver needs no kernel parameters. All supported devices
  23 present are detected on driver initialization at system startup or module load.
  24 The devices detected are ordered by their subchannel numbers. The device with
  25 the lowest subchannel number becomes device 0, the next one will be device 1
  26 and so on.
  27
  28
  29 Tape character device front-end
  30
  31 The usual way to read or write to the tape device is through the character
  32 device front-end. The zSeries tape device driver provides two character devices
  33 for each physical device -- the first of these will rewind automatically when
  34 it is closed, the second will not rewind automatically.
  35
  36 The character device nodes are named /dev/rtibm0 (rewinding) and /dev/ntibm0
  37 (non-rewinding) for the first device, /dev/rtibm1 and /dev/ntibm1 for the
  38 second, and so on.
  39
  40 The character device front-end can be used as any other LINUX tape device. You
  41 can write to it and read from it using LINUX facilities such as GNU tar. The
  42 tool mt can be used to perform control operations, such as rewinding the tape
  43 or skipping a file.
  44
  45 Most LINUX tape software should work with either tape character device.
  46
  47
  48 Tape block device front-end
  49
  50 The tape device may also be accessed as a block device in read-only mode.
  51 This could be used for software installation in the same way as it is used with
  52 other operation systems on the zSeries platform (and most LINUX
  53 distributions are shipped on compact disk using ISO9660 filesystems).
  54
  55 One block device node is provided for each physical device. These are named
  56 /dev/btibm0 for the first device, /dev/btibm1 for the second and so on.
  57 You should only use the ISO9660 filesystem on LINUX for zSeries tapes because
  58 the physical tape devices cannot perform fast seeks and the ISO9660 system is
  59 optimized for this situation.
  60
  61
  62 Tape block device example
  63
  64 In this example a tape with an ISO9660 filesystem is created using the first
  65 tape device. ISO9660 filesystem support must be built into your system kernel
  66 for this.
  67 The mt command is used to issue tape commands and the mkisofs command to
  68 create an ISO9660 filesystem:
  69
  70 - create a LINUX directory (somedir) with the contents of the filesystem
  71      mkdir somedir
  72      cp contents somedir
  73
  74 - insert a tape
  75
  76 - ensure the tape is at the beginning
  77      mt -f /dev/ntibm0 rewind
  78
  79 - set the blocksize of the character driver. The blocksize 2048 bytes
  80   is commonly used on ISO9660 CD-Roms
  81      mt -f /dev/ntibm0 setblk 2048
  82
  83 - write the filesystem to the character device driver
  84      mkisofs -o /dev/ntibm0 somedir
  85
  86 - rewind the tape again
  87      mt -f /dev/ntibm0 rewind
  88
  89 - Now you can mount your new filesystem as a block device:
  90      mount -t iso9660 -o ro,block=2048 /dev/btibm0 /mnt
  91
  92 TODO List
  93
  94    - Driver has to be stabilized still
  95
  96 BUGS
  97
  98 This driver is considered BETA, which means some weaknesses may still
  99 be in it.
 100 If an error occurs which cannot be handled by the code you will get a
 101 sense-data dump.In that case please do the following:
 102
 103 1. set the tape driver debug level to maximum:
 104      echo 6 >/proc/s390dbf/tape/level
 105
 106 2. re-perform the actions which produced the bug. (Hopefully the bug will
 107    reappear.)
 108
 109 3. get a snapshot from the debug-feature:
 110      cat /proc/s390dbf/tape/hex_ascii >somefile
 111
 112 4. Now put the snapshot together with a detailed description of the situation
 113    that led to the bug:
 114  - Which tool did you use?
 115  - Which hardware do you have?
 116  - Was your tape unit online?
 117  - Is it a shared tape unit?
 118
 119 5. Send an email with your bug report to:
 120      mailto:Linux390@de.ibm.com
 121
 122