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Linus Torvalds1da177e2005-04-16 15:20:36 -07001Channel attached Tape device driver
2
3-----------------------------WARNING-----------------------------------------
4This driver is considered to be EXPERIMENTAL. Do NOT use it in
5production environments. Feel free to test it and report problems back to us.
6-----------------------------------------------------------------------------
7
8The LINUX for zSeries tape device driver manages channel attached tape drives
9which are compatible to IBM 3480 or IBM 3490 magnetic tape subsystems. This
10includes various models of these devices (for example the 3490E).
11
12
13Tape driver features
14
15The device driver supports a maximum of 128 tape devices.
16No official LINUX device major number is assigned to the zSeries tape device
17driver. It allocates major numbers dynamically and reports them on system
18startup.
19Typically it will get major number 254 for both the character device front-end
20and the block device front-end.
21
22The tape device driver needs no kernel parameters. All supported devices
23present are detected on driver initialization at system startup or module load.
24The devices detected are ordered by their subchannel numbers. The device with
25the lowest subchannel number becomes device 0, the next one will be device 1
26and so on.
27
28
29Tape character device front-end
30
31The usual way to read or write to the tape device is through the character
32device front-end. The zSeries tape device driver provides two character devices
33for each physical device -- the first of these will rewind automatically when
34it is closed, the second will not rewind automatically.
35
36The 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
38second, and so on.
39
40The character device front-end can be used as any other LINUX tape device. You
41can write to it and read from it using LINUX facilities such as GNU tar. The
42tool mt can be used to perform control operations, such as rewinding the tape
43or skipping a file.
44
45Most LINUX tape software should work with either tape character device.
46
47
48Tape block device front-end
49
50The tape device may also be accessed as a block device in read-only mode.
51This could be used for software installation in the same way as it is used with
52other operation systems on the zSeries platform (and most LINUX
53distributions are shipped on compact disk using ISO9660 filesystems).
54
55One 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.
57You should only use the ISO9660 filesystem on LINUX for zSeries tapes because
58the physical tape devices cannot perform fast seeks and the ISO9660 system is
59optimized for this situation.
60
61
62Tape block device example
63
64In this example a tape with an ISO9660 filesystem is created using the first
65tape device. ISO9660 filesystem support must be built into your system kernel
66for this.
67The mt command is used to issue tape commands and the mkisofs command to
68create 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
92TODO List
93
94 - Driver has to be stabilized still
95
96BUGS
97
98This driver is considered BETA, which means some weaknesses may still
99be in it.
100If an error occurs which cannot be handled by the code you will get a
101sense-data dump.In that case please do the following:
102
1031. set the tape driver debug level to maximum:
104 echo 6 >/proc/s390dbf/tape/level
105
1062. re-perform the actions which produced the bug. (Hopefully the bug will
107 reappear.)
108
1093. get a snapshot from the debug-feature:
110 cat /proc/s390dbf/tape/hex_ascii >somefile
111
1124. 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
1195. Send an email with your bug report to:
120 mailto:Linux390@de.ibm.com
121
122