1 Intro
2 =====
3
4 This file describes some issues involved when using the "ftape"
5 floppy tape device driver that comes with the Linux kernel. This
6 document deals with ftape-3.04 and later. Please read the section
7 "Changes" for the most striking differences between version 3.04 and
8 2.08; the latter was the version of ftape delivered with the kernel
9 until kernel version 2.0.30 and 2.1.57. ftape-3.x developed as the
10 re-unification of ftape-2.x and zftape. zftape was developed in
11 parallel with the stock ftape-2.x driver sharing the same hardware
12 support but providing an enhanced file system interface. zftape also
13 provided user transparent block-wise on-the-fly compression (regard it
14 as a feature or bug of zftape).
15
16 ftape has a home page at
17
18 http://www-math.math.rwth-aachen.de/~LBFM/claus/ftape
19
20 which contains further information about ftape. Please cross check
21 this WWW address against the address given (if any) in the MAINTAINERS
22 file located in the top level directory of the Linux kernel source
23 tree.
24
25 Contents
26 ========
27
28 A minus 1: Ftape documentation
29
30 A. Changes
31 1. Goal
32 2. I/O Block Size
33 3. Write Access when not at EOD (End Of Data) or BOT (Begin Of Tape)
34 4. MTBSF - backspace over file mark and position at its EOT side
35 5. Formatting
36 6. Interchanging cartridges with other operating systems
37
38 B. Debugging Output
39 1. Introduction
40 2. Tuning the debugging output
41
42 C. Boot and load time configuration
43 1. Setting boot time parameters
44 2. Module load time parameters
45 3. Ftape boot- and load time options
46 4. Example kernel parameter setting
47 5. Example module parameter setting
48
49 D. Support and contacts
50
51 *******************************************************************************
52
53 A minus 1. Ftape documentation
54 ==============================
55
56 Unluckily, the ftape-HOWTO is out of date. This really needs to be
57 changed. Up to date documentation as well as recent development
58 versions of ftape and useful links to related topics can be found at
59 the ftape home page at
60
61 http://www-math.math.rwth-aachen.de/~LBFM/claus/ftape
62
63 *******************************************************************************
64
65 A. Changes
66 ==========
67
68 1. Goal
69 ~~~~
70 The goal of all that incompatibilities was to give ftape an interface
71 that resembles the interface provided by SCSI tape drives as close
72 as possible. Thus any Unix backup program that is known to work
73 with SCSI tape drives should also work with ftape-3.04 and above.
74
75 The concept of a fixed block size for read/write transfers is
76 rather unrelated to this SCSI tape compatibility at the file system
77 interface level. It developed out of a feature of zftape, a
78 block wise user transparent on-the-fly compression. That compression
79 support will not be dropped in future releases for compatibility
80 reasons with previous releases of zftape.
81
82 2. I/O Block Size
83 ~~~~~~~~~~~~~~
84 The probably most striking difference between ftape-2.x and
85 ftape-3.x with the zftape file system interface is the concept of a
86 fixed block size: data must be written to or read from the tape in
87 multiples of a fixed block size. The block size defaults to 10k
88 which is the default block size of GNU tar. While this is quite
89 usual for SCSI tapes (block size of 32k?) and the QIC-150 driver
90 `./drivers/char/tpqic02.c' ftape-2.x allowed data to be written in
91 arbitrary portions to the tape.
92
93 The block size can be tuned either during kernel configuration or
94 at runtime with the MTIOCTOP ioctl using the MTSETBLK operation
95 (i.e. do "mt -f /dev/qft0" setblk #BLKSZ). A block size of 0
96 switches to variable block size mode i.e. "mt setblk 0" switches
97 off the block size restriction. However, this disables zftape's
98 built in on-the-fly compression which doesn't work with variable
99 block size mode.
100
101 The BLKSZ parameter must be given as a byte count and must be a
102 multiple of 32k or 0, i.e. use "mt setblk 32768" to switch to a
103 block size of 32k.
104
105 The typical symptom of a block size mismatch is an "invalid
106 argument" error message.
107
108 3. Write Access when not at EOD (End Of Data) or BOT (Begin Of Tape)
109 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
110 zftape (the file system interface of ftape-3.x) denies write access
111 to the tape cartridge when it isn't positioned either at BOT or
112 EOD. This inconvenience has been introduced as it was reported that
113 the former behavior of ftape-2.x which allowed write access at
114 arbitrary locations already has caused data loss with some backup
115 programs.
116
117 4. MTBSF - backspace over file mark and position at its EOT side
118 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
119 ftape-2.x didn't handle the MTBSF tape operation correctly. A MTBSF
120 call (i.e. "mt -f /dev/nqft0 bsf #COUNT") should space over #COUNT
121 file marks and then position at the EOT tape side of the file
122 mark. This has to be taken literally, i.e. "mt -f /dev/nqft0 bsf 1"
123 should simply position at the start of the current volume.
124
125 5. Formatting
126 ~~~~~~~~~~
127 ftape-3.x DOES support formatting of floppy tape cartridges. You
128 need the `ftformat' program that is shipped with the modules version
129 of ftape-3.x. Please get the latest version of ftape from
130
131 ftp://sunsite.unc.edu/pub/Linux/kernel/tapes
132
133 or from the ftape home page at
134
135 http://www-math.math.rwth-aachen.de/~LBFM/claus/ftape
136
137 `ftformat' is contained in the `./contrib/' subdirectory of that
138 separate ftape package.
139
140 6. Interchanging cartridges with other operating systems
141 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
142
143 The internal emulation of Unix tape device file marks has changed
144 completely. ftape-3.x now uses the volume table segment as specified
145 by the QIC-40/80/3010/3020/113 standards to emulate file marks. As
146 a consequence there is limited support to interchange cartridges
147 with other operating systems.
148
149 To be more precise: ftape will detect volumes written by other OS's
150 programs and other OS's programs will detect volumes written by
151 ftape-3.x.
152
153 However, it isn't possible to extract the data dumped to the tape
154 by some MSDOG program with ftape-3.x. This exceeds the scope of a
155 kernel device driver. If you need such functionality, then go ahead
156 and write a user space utility that is able to do
157 that. ftape-3.x/zftape already provides all kernel level support
158 necessary to do that.
159
160 *******************************************************************************
161
162 B. Debugging Output
163 ================
164
165 1. Introduction
166 ~~~~~~~~~~~~
167 The ftape driver can be very noisy in that is can print lots of
168 debugging messages to the kernel log files and the system console.
169 While this is useful for debugging it might be annoying during
170 normal use and enlarges the size of the driver by several kilobytes.
171
172 To reduce the size of the driver you can trim the maximal amount of
173 debugging information available during kernel configuration. Please
174 refer to the kernel configuration script and its on-line help
175 functionality.
176
177 The amount of debugging output maps to the "tracing" boot time
178 option and the "ft_tracing" modules option as follows:
179
180 0 bugs
181 1 + errors (with call-stack dump)
182 2 + warnings
183 3 + information
184 4 + more information
185 5 + program flow
186 6 + fdc/dma info
187 7 + data flow
188 8 + everything else
189
190 2. Tuning the debugging output
191 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
192 To reduce the amount of debugging output printed to the system
193 console you can
194
195 i) trim the debugging output at run-time with
196
197 mt -f /dev/nqft0 setdensity #DBGLVL
198
199 where "#DBGLVL" is a number between 0 and 9
200
201 ii) trim the debugging output at module load time with
202
203 insmod ftape.o ft_tracing=#DBGLVL
204
205 Of course, this applies only if you have configured ftape to be
206 compiled as a module.
207
208 iii) trim the debugging output during system boot time. Add the
209 following to the kernel command line:
210
211 ftape=#DBGLVL,tracing
212
213 Please refer also to the next section if you don't know how to
214 set boot time parameters.
215
216 *******************************************************************************
217
218 C. Boot and load time configuration
219 ================================
220
221 1. Setting boot time parameters
222 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
223 Assuming that you use lilo, the LI)nux LO)ader, boot time kernel
224 parameters can be set by adding a line
225
226 append some_kernel_boot_time_parameter
227
228 to `/etc/lilo.conf' or at real boot time by typing in the options
229 at the prompt provided by LILO. I can't give you advice on how to
230 specify those parameters with other loaders as I don't use them.
231
232 For ftape, each "some_kernel_boot_time_parameter" looks like
233 "ftape=value,option". As an example, the debugging output can be
234 increased with
235
236 ftape=4,tracing
237
238 NOTE: the value precedes the option name.
239
240 2. Module load time parameters
241 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
242 Module parameters can be specified either directly when invoking
243 the program 'insmod' at the shell prompt:
244
245 insmod ftape.o ft_tracing=4
246
247 or by editing the file `/etc/modules.conf' in which case they take
248 effect each time when the module is loaded with `modprobe' (please
249 refer to the modules documentation, i.e. `modules.txt' and the
250 respective manual pages). Thus, you should add a line
251
252 options ftape ft_tracing=4
253
254 to `/etc/modules.conf` if you intend to increase the debugging
255 output of the driver.
256
257
258 3. Ftape boot- and load time options
259 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
260
261 i. Controlling the amount of debugging output
262 DBGLVL has to be replaced by a number between 0 and 8.
263
264 module | kernel command line
265 -----------------------|----------------------
266 ft_tracing=DBGLVL | ftape=DBGLVL,tracing
267
268 ii. Hardware setup
269 BASE is the base address of your floppy disk controller,
270 IRQ and DMA give its interrupt and DMA channel, respectively.
271 BOOL is an integer, "0" means "no"; any other value means
272 "yes". You don't need to specify anything if connecting your tape
273 drive to the standard floppy disk controller. All of these
274 values have reasonable defaults. The defaults can be modified
275 during kernel configuration, i.e. while running "make config",
276 "make menuconfig" or "make xconfig" in the top level directory
277 of the Linux kernel source tree. Please refer also to the on
278 line documentation provided during that kernel configuration
279 process.
280
281 module | kernel command line
282 -----------------------|----------------------
283 ft_fdc_base=BASE | ftape=BASE,ioport
284 ft_fdc_irq=IRQ | ftape=IRQ,irq
285 ft_fdc_dma=DMA | ftape=DMA,dma
286 ft_probe_fc10=BOOL | ftape=BOOL,fc10
287 ft_mach2=BOOL | ftape=BOOL,mach2
288 ft_fdc_threshold=THR | ftape=THR,threshold
289 ft_fdc_rate_limit=RATE | ftape=RATE,datarate
290
291 4. Example kernel parameter setting
292 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
293 To configure ftape to probe for a Colorado FC-10/FC-20 controller
294 and to increase the amount of debugging output a little bit, add
295 the following line to `/etc/lilo.conf':
296
297 append ftape=1,fc10 ftape=4,tracing
298
299 5. Example module parameter setting
300 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
301 To do the same, but with ftape compiled as a loadable kernel
302 module, add the following line to `/etc/modules.conf':
303
304 options ftape ft_probe_fc10=1 ft_tracing=4
305
306 *******************************************************************************
307
308 D. Support and contacts
309 ====================
310
311 Ftape is distributed under the GNU General Public License. There is
312 absolutely no warranty for this software. However, you can reach
313 the current maintainer of the ftape package under the email address
314 given in the MAINTAINERS file which is located in the top level
315 directory of the Linux kernel source tree. There you'll find also
316 the relevant mailing list to use as a discussion forum and the web
317 page to query for the most recent documentation, related work and
318 development versions of ftape.
319
320
321 LocalWords: ftape Linux zftape http www rwth aachen LBFM claus EOD config
322 LocalWords: datarate LocalWords BOT MTBSF EOT HOWTO QIC tpqic menuconfig
323 LocalWords: MTIOCTOP MTSETBLK mt dev qft setblk BLKSZ bsf zftape's xconfig
324 LocalWords: nqft ftformat ftp sunsite unc edu contrib ft MSDOG fdc
325 LocalWords: dma setdensity DBGLVL insmod lilo LI nux ader conf txt
326 LocalWords: modprobe IRQ BOOL ioport irq fc mach THR
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