7 Frequently Asked Questions

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This is a collection of questions I get asked once in a while, which could fall into the category of FAQ's. If you feel that there is some question that ought to be added to the list, please feel free to mail me (but do include an answer, thanks!).

7.1 Can I exchange tapes with someone using DOS?

No. The DOS software conforms to the QIC-80 specs about the layout of the DOS filesystem, and it should(?) be a small problem to write a program that can read/write the DOS format. In fact, I'd bet that creating a nice user interface would be a bigger problem.

7.2 How do I `....' with tar?

These are really tar questions: Please read the man page and the info page. If you have not got it either, try `tar --help 2>&1 | more'.

If your version of tar is v1.11.1 or earlier, consider upgrading to v1.11.2 - This version can call GNU zip directly (i.e.: it supports the -z option) and has an elaborate help included. Also, it compiles right out of the box on Linux.

7.3 ftape DMA transfers gives ECC errors

Sadly to say there are some SVGA cards and ethernet cards that do not decode their addresses correct. This typically happens when the ftape buffers are in the range 0x1a0000 to 0x1c0000. Somehow, the DMA write cycles get clobbered and every other byte written gets a bad value (0xff). These problems are reported to happen with both SVGA and ethernet cards. We know of at least one (bad?) ATI 16bit VGA card that caused this.

The easiest solution is to put the card in an 8bit slot (it is often not enough to reconfigure the card to 8bit transfers). Moving the ftape buffer away from the VGA range is only a partial solution; All DMA buffers used in Linux can have this problem! Let us make this one clear: This has nothing to do with the ftape software.

7.4 insmod says the kernel version is wrong

The insmod program checks the kernel version against the version recorded in the ftape driver. This is a string in kernel-version.h, (e.g.: #define KERNEL_VERSION "1.1.72";) which is extracted from the kernel you are running when you run `make dep'. If you got the error when you tried to insert the ftape driver, remove the file `kernel-version.h', type `make dep; make' again and the kernel-version.h file should be updated. Remember that you will have to do this every time you change to another kernel version.

7.5 The v1.1.0 kernel wont compile when ftape support is added

(Although I haven't heard a lot of complains, I include it here, just to be sure)

This was due to a typo (and a hacker who didn't use ftape himself, so he never got around to actually test the code he wrote). This is corrected by patch1.gz, which can be found from the usual ftp sites.

7.6 ftape complains that ``This tape has no 'Linux raw format'''

If you get this complaint, try `mt -f /dev/ftape erase'. This should solve the problem.

7.7 Where can I find the tar/mt/cpio/dd binaries/sources/manpages?

All of these tools have been developed by the GNU project, and the source (and man page) can be fetched from just-about any ftp site in the world (including ftp.funet.fi, tsx-11.mit.edu, and sunsite.unc.edu). In any case they can be fetched from the official GNU home site: prep.ai.mit.edu [18.71.0.38]:/pub/gnu. The latest versions (by 26. march 94) are:

        cpio:   2.3 (cpio-2.3.tar.gz)
        dd:     3.9 (fileutils-3.9.tar.gz)
        mt:     2.3 (cpio-2.3.tar.gz)
        tar:    1.11.2 (tar-1.11.2.tar.gz)
        gzip:   1.2.4 (gzip-1.2.4.tar.gz)

They all compile out of the box on Linux v1.0.4 / libc v4.5.19 / gcc v2.5.8 (The rmt program does not compile out of the box, but it is not needed as it is only used for accessing the tape drive remotely).

7.8 Where can I obtain the QIC standards?

If you wish to help developing ftape, or add some utility (e.g. a tape formatting program), you will need that appropriate QIC standards. The standard(s) to get is: QIC-80 and perhaps QIC-117. QIC-117 describes how commands are sent to the tape drive (including timing etc), so you would probably never need it. QIC-80 describes the tape layout, ECC code, standard filesystem and all such ``higher-level'' stuff. You can get the QIC standards from the following address:

Quarter Inch Cartridge Drive Standars, Inc.
311 East Carrillo Street
Santa Barbara, California 93101
Phone: (805) 963-3852
Fax:   (805) 962-1541

7.9 What block-size to use with tar

When using compression, and in all general, it can be a benefit to specify to tar, that it should block the output into chunks. Since ftape cuts things into 29Kbyte blocks, saying `-b58' should be optimum.

``Why 29Kbyte?'', I hear you cry. Well, the QIC-80 standard specifies that all data should be protected by an Error Correcting Code (ECC) code. The code that ftape uses is known as a Reed-Solomon (R-S) code. The R-S code that ftape uses takes 29 data bytes and generates 3 parity bytes, which are appended and written to the tape together with the data, effectively making 32Kbytes. For this reason, ftape will always read 32K byte blocks to be able to detect (and correct) data errors.

If you are curious, and wish to know more, look in the ecc.c and ecc.h files, they an explanation of the code and reference to a textbook on Reed-Solomon codes.

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