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You can achieve quite respectable backup and restore speeds with
Ftape: a Colorado DJ-20 and an Adaptec 1542CF controller, has
been measured at 4.25Mbyte/min sustained data transfer rate (no
compression) across a 70Mbyte tar archive, while comparing the archive
on the tape with data on an IDE disk. The speed of Ftape is
mostly dependent on the data transfer rate of your FDC: The AHA1542CF
has a ``post-1991 82077'' FDC, and it will push 1Mbit/sec at the tape
drive. If you have an FDC which can only deliver 500Kbit/sec data
rates, you will see half the transfer rate (well, roughly).
There has been a few reports of "shoeshining". This is when the tape just
seems to run back and forth endlessly. This has been seen on a Jumbo
250 (74407.3051@compuserve.com) and on an Iomega 250 Ditto Insider
(tom@opus.cais.com). In the latter case it has been narrowed own to
using an ELF Linux and running off a SCSI hard disk (connected to an
Adaptec 1542cf). Please contact me if you have an update to this
problem.
<from the Ftape-Howto>
Probably not. If you are backing up a large number of < 2K files, you're
just going to have to live with it. In this event, the repositions are caused
by file system access overhead. If you are backing up a normal system's files,
this may be caused by slop or media stretching in the tape cartridge. By
simply retensioning the tape, you should see this go away. Try
ftmt -f /dev/zqft0 reten
to retension the tape. If retensioning doesn't solve this, and it's only
happening on certain tapes, it might be wise to replace the tapes in question.
<answer from Tim Jones>
If you use afio as your backup tool you can set it to write a very large
number of buffers in one hit by using the -c flag. Make it large enough so
that you supply enough data for most of a single end-to-end pass over the tape.
For my system, the following streams quite nicely - stopping relatively few
times per tape pass on an unloaded system:
find /usr/local -xdev -print | afio -o -v -f -b 10240 -c 800 /dev/qft0
In my case I'm writing 800 x 10240 bytes per tape write, i.e. about 8MB.
haven't experimented that much with these settings - so someone might like
to establish more optimal ones.
Presumably other backup utilities could be modified to use a similar technique.
<answer by Michael Hamilton>
GNU tar doesn't use buffering in this way. The commercial backup program
"bru" is able to multi-buffer using shared memory; this works only when
writing compressed archive with bru (regardless whether you use Ftape's
builtin compression)
Another way to overcome the problem might be to use more dma buffers in the
Ftape kernel driver like:
mt -f /dev/qft0 setdrvbuffer $((6*32786))
$((6*32786)) should be expanded by your shell when using a Bourne
compatible one. This has a negative impact on the system's memory pool:
Ftape's dma buffers cannot be used by any other part of the kernel nor
by any other application. And kernel memory cannot be swapped out. If you
decide to use this kind of multi-buffering then you should unload the driver
as soon as it isn't needed any longer.
<answer by Claus Heine>
Not if you are using the latest version of the Ftape drivers from the
Ftape Home Page.
To format a QIC-80, TR-1, TR-3, QICWide 3010 or 3020 tape, get the
latest version of ftape and the latest version of the
ftape-tools package (from the same location) and read the
documentation of the ftformat utility which is included in the
ftape-tools package.
Comment
Do not try to format Ditto 2GB tapes.
Comment
Do not try to format Ditto Max or Max Pro tapes.
<answers from Tim Jones and Claus Heine>
It isn't possible to format Ditto 2GB tapes with Ditto 2GB
tape drive, and it isn't possible at all to re-format Ditto 2GB
tapes in a way that they still can be used by a Ditto 2GB tape
drive.
This is a hardware limitation of the Ditto 2GB tape drive. It
can't be helped at the software level, i.e. it isn't ftape's
fault.
No, the Ditto Max can't format tapes.
This is a hardware limitation of the Ditto Max (Pro) tape drive. It
can't be helped at the software level, i.e. it isn't ftape's
fault.
If you look at the difference, you will notice that Ftape
always detects 2784 sectors more than DOS.
The number that Ftape reports is correct (of course :-) . Each
correctly formatted QIC-3020 tape has 2784 sectors at fixed positions
that are marked in the bad sector map. To quote from the specs:
Tracks 5,7,9,11,13,15,17,19,21,23,25 and 27 within 4 segments of
either EOT or BOT are prone to increased error rates due to hole
imprints. Therefore, these regions shall be mapped as bad at format
time and entered in the bad sector map by indicating that all sectors
within the identified segments are bad.
This gives 12 tracks * 2 * 4 segments * 29 sectors == 2784 sectors.
So Ftape choose to report the real number of sectors that cannot be
used on the tape, while DOS gives a more optimistic number giving a
better indication of tape quality. (Ftape's behavior might change in
the future to detect correct formatting and display the separate
numbers. It has rather low priority though).
QIC-3010 are alike QIC-3020 tapes regarding this.
<from the Ftape-Howto>
Yes. The driver merely updates an internal counter when those
commands are issues. The tape should move to the proper location on
the next read or write access to the tape drive.
<from the Ftape-Howto>
zftape requires the data to be written in multiples of a fixed minimal
block size. This is a very usual behavior for a tape device. There are three
ways to get rid of those errors:
- set Ftape's block size to the block size used by the backup program. The example below works for "afio":
mt -f /dev/qft0 setblk 5120
- If you don't want to use Ftape's built in compression you can also use
mt -f /dev/qft0 setblk 0
to switch Ftape to variable block size mode and be able to write the
data in arbitrary portions to the tape (BUT: the builtin compression doesn't
work with this setting). When you intend to use "KBackup" then this is the
only way to make it work together with Ftape (it _may_ work, don't know
if it does)
- tell your backup program about Ftape's default block size of 10k (which
is also the default of GNU tar). For "afio" you can use the following command
line switch:
afio -b 10k ...
You may want to read the section "Tape blocks" of the manual (use its
"Concept index" to directly jump to that section)
When using GNU tar's builtin compression with GNU tar versions prior to
tar-1.12 one needs to run tar with the --block-compress switch to
re-block the output to the tape. Otherwise tar will compress the data
it reads, and write it in arbitrary portions to the tape.
Example :
tar -czvf /dev/qft0 --block-compress /etc
WARNING:
One shouldn't use tar's builtin compression with large backups as it makes the
entire data stream one huge compressed block. If such archives are corrupted
right at the beginning it will be very difficult to recover.
<answer by Claus Heine>
When you get next messages, this could be interesting for you !
- fdc-io.c (ft_handle_perpend) - Your FDC does not support QIC-3020.
- Cannot write to /dev/qft0: I/O error
The explanations:
"FDC" menas "Floppy Disk Controller". The
problem is that your floppy disk controller must be able to support
something that is called "perpendicular mode" to be able to read and
write QIC-3020/QIC-3010 cartridges (i.e. TR-3 cartridges). To my
knowledge all FDCs that are capable of at least 1Mbit/sec data
transfer rate also support "perpendicular mode" ("perpendicular"
refers to the direction of magnetization of the ferro-magnetic
particles on the tape).
This means that you need to purchase another FDC. Either look around
some computer stores and ask for an IO controller cards that is able
to support 2.88 Mb floppies (which imlies 1Mbit data transfer rate and
perpendicular mode).
Or get one of the so called "high speed" controllers that even support
2Mbit/sec data transfer rate. Those controllers are based on an Intel
82078 FDC. Iomega sells such a card under the name "Ditto Dash". I
think Exabyte sells their 2Mbit controllers separately, too, whereas
Seagate ships its TR-3 drives (i.e. the TST-3200) together with such a
controller.
<answer from Claus Heine>
I assume that the following is the problem:
The Ftape module is loaded OK into the kernel:
/usr/src/ftape-3.03b-970603# lsmod
Module Pages Used by
ftape 22 0
but then this happens:
$ ftmt -f /dev/qft0 status
ftmt: /dev/qft0: No such device
Solution
You need to load the zftape.o module as well. With Ftape-3.* the
ftape.o module doesn't implement the VFS interface. This is done by
zftape.o.
<answer from Claus Heine>
The "device busy" messages can only occur while the Ftape devices are
still held open by some program. As soon as the close() system call has
completed the busy flag is cleared. May be "bru" or some other program has
still forked off a child that dies delayed?
Yes, this will reproduce the problem, it seems:
tar -cvvzf /dev/nqft0 --block-compress ; mt rewind
You can skip the "--block-compress" if using the most recent version
of GNU tar.
However, this is not a bug of Ftape. It seems that the parent tar
process exits before its child has closed the tape device. I know,
however, from hacking the tar code ages ago, that tar properly waits
for its parent to die.
However, the busy message simply means that the "busy" variable is
still held at 1 (zftape/zftape-init.c). And this simply means that
there still is a process hanging around that holds the tape device
open.
I think I have it (only for the case of tar 'cause I have the source
code.
If on uses tar with compression, then it forks a child which will
become the compressor bei execing "gzip" or whatever. Before the call
to execlp() the child will fork off a grand child of its parent
tar. That grandchild will do the actual tape I/O.
tar - fork() - write to child tar
|
child tar - fork() - gzip (will pipe to grand child tar)
|
grand child tar - open archive.
Now, parent tar only waits for its child to die. gzip surely doesn't
wait for the grand child as the gzip is a result of an execlp().
What I don't know is whether the grand child should be implicitly
waited for by the parent tar, or if the wait() function also waits for
grand childs.
But this seems to be the problem: the parent tar already has exited
while its grandchild still is busy closing the archive. One hardly
will notice this problem if the close() happens fast (i.e. regular
files, block devices, also other tape devices?), but it isn't a bug in
Ftape, but either in the backup programs or in the kernel or maybe
libc exit code.
Don't know if the considerations above also apply to bru. If there is
no grandchild and the parent process properly waits for its childs
then there shouldn't be a problem.
<answer from Claus Heine>
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 | less
If your version of tar is v1.11.1 or earlier, consider
upgrading to v1.11.8 - 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.
<from the Ftape-Howto>
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 specified in the QIC-80 standard is known as a
Reed-Solomon (R-S) code. The R-S code takes 29 data bytes and
generates 3 parity bytes. To increase the performance of the ECC
code, the parity bytes are generated across 29 1Kbyte sectors. Thus,
Ftape takes 29Kbytes of data, adds 3Kbytes of ECC parity, and
writes 32Kbytes to the tape at a time. For this reason, Ftape will
always read and write 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, for an explanation of the code and a reference to a
textbook on Reed-Solomon codes.
<from the Ftape-Howto>
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 (as of September 12
1996) are:
cpio: 2.4.2 (cpio-2.4.2.tar.gz)
dd: 3.13 (fileutils-3.13.tar.gz)
mt: 2.4.2 (cpio-2.4.2.tar.gz)
tar: 1.11.8 (tar-1.11.8.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 .
<from the Ftape-Howto>
It is not bad as such to compress data twice (which would be the case
when using tapers compression together with zftape's compression) but
it doesn't make any sense. You won't gain much further compression,
but only waste CPU cycles.
Tapers compression should be quite safe, as taper compresses single
files; in contrast to tar -czf ... which makes the entire data
stream a large compressed block of data, which is really a bad thing
with serious backups as a single bad byte at the beginning of the
archive can make the entire archive unusable, well, it will be at
least quite difficult to recover.
<Answer from Claus Heine>
gzip -9 is better (i.e. one gains higher compression). zftape's
compression is comparable with the Un*x compress program, but should
be faster, and is faster than gzip.
<Answer from Claus Heine>
Use the zftape interface, but don't load the zft-compressor module.
The device then becomes /dev/qft0 .
<answer from Tim Jones>
You get this complaint if you haven't erased your freshly
formatted tape. This is because Ftape expect a "magic header"
on the tape, to be able that it is allowed to interpret the header
segment in its own way (eg: file marks). To remove the problem, say
mt -f /dev/nftape erase
<from the Ftape-Howto>
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.
<From the Ftape-Howto>
(EOM is "End Of recorded Media", the position right after all data
already recorded to the tape)
One cannot use tape "files" like files on an ordinary file system.
In principle, a tape doesn't allow anything but appending new data at
EOM. However, if one positiones just in the middle of the already
recorded data AND starts writing, then the driver first deletes all
following files (thus moving the EOM to the actual position) and then
starts writing.
Thus, the new EOM after finishing the write process, is then after the
newly recorded data.
One of the consequences of the above is, of course, that writing to
the tape in the middle of the already recorded area, is destructive in
the sense, that it not only overwrites the "file" the tape is
positioned at, but also deletes all following files.
<from the Ftape-Howto>
<Answer from Claus Heine>
It probably didn't work before because you didn't use a
mt -f /dev/rft0 erase
before writing data to the cartridge. THIS ISN'T necessary any more.
But, hey, what does mt fsf? Tape drives don't store files in the
sense that you can use
cp somefile /dev/my_what_ever_tape
or be able to mount the tape drive like you could mount a harddisk.
You can't do nothing with a tape drive but write data to it in a sequential
manner.
As this is quite inconvenient, somebody invented something which is
known under the name file mark or eof mark (eof == End Of
File). Those marks don't separate files that have been backed up to
the tape device, but only separate blocks of data (whatever data that
might be).
Normally, the kernel tape device drivers take care of writing file
marks when the tape device is closed, i.e.
tar -cf /dev/nqft0 /bin
tar -cf /dev/nqft0 /etc
mt -f /dev/nqft0 rewind
would result in a backup of all files under /bin and /etc. When
the first tar finishes, the kernel driver will take care of writing
a file mark to the tape at the the current tape position, and when the
second tar process has finished, another file mark is written to the
tape cartridge at that position.
Now, the sense of those file marks is, that it is possible to skip
between different archives on the tape more quickly than would be
possible with reading the data back.
The commands to do that are:
- mt fsf
fast skip to the next file mark towards EOT (End Of Tape)
- mt bsf
fast skip to the next file marks towards BOT (Begin Of Tape)
Thus, to extract the second archive in the example above, one doesn't
need to read the first archive back, but can proceed as follows:
mt -f /dev/nqft0 rewind
mt -f /dev/nqft0 fsf
tar -xvf /dev/nqft0
<Answer from Claus Heine>
When Ftape was young there were two versions of the floppy tape
driver, one of them was called zftape because of its built-in
user-transparent on-the-fly compression. Whether such a thing is a
feature or a bug ('cause this needn't be done in kernel space) is
another question. However, the ioctl interface and file mark handling
provided by zftape was much better and had less bugs. And zftape
allows to use floppy tape cartridges with different OS. Well, you
can't exchange data, but zftape won't overwrite volumes created by
your Windoze program, and vice versa.
Nowadays, Ftape is name of the entire floppy tape driver package AND
ftape.o is the file-name of the kernel module that implements the
low-level hardware support. zftape has ceased to exist as a separate
package, but the new Ftape versions (since ftape-3.00) contain a
zftape.o module that needs to be loaded on top of ftape.o
(i.e. you need to load BOTH modules to be able to access your floppy
tape drive) and implements the file system interface and the advanced
(?) features of the previous verions zftape.
<Answer from Claus Heine>
Well, the rewinding tape devices rewind the tape to BOT (Begin Of
Tape) when the device is closed, i.e.
tar -cvf /dev/qft0 /bin
will rewind the tape cartridge when the tar job has finished. In contrast,
tar -cvf /dev/nqft0 /bin
will NOT rewind the tape cartridge and leave the tape R/W head at its
current position.
Rewinding devices should be used when performing a single backup,
non-rewinding devices can be useful when doing multiple backups as one
doesn't need to space to EOM (End Of recorded Media) before appending
another archive.
Non-rewinding devices MUST be used when sending any of the tape motion
command to the tape drive, such as
mt -f /dev/nqft0 fsf
, because when the mt process finishes then the tape device is closed
which would result in rewinding the cartridge with the rewinding devices.
<Answer from Claus Heine>
Well, it depends. If the tape is still positioned inside the volume
just written, "mt bsf 1" (or equivalently "mt bsf") will backspace
just to the beginning of that volume (this is how "tar --verify"
works). If the tape is already positioned AFTER the filemark that
marks the end of the last written volume, then you need to issue
"mt bsf 2"
The logic behind this is as follows:
"MTBSF count" backspaces over count file marks, stops, and then
positions on the EOT side of the last skipped file mark. This means,
an "mt bsf 2" will position right at the beginning of the previous
volume.
<answer form Claus Heine>
You are right: auto-rewind means, the tape is rewound when the tape
device is closed, non-rewinding means, the tape isn't automatically
rewound when the tape device is closed (but you can, of course, use
the tape motion commands BSF/FSF etc. to position the tape head at
every position you like).
<answer form Claus Heine>
A record is the minimal amount of bytes that will be accepted by the
tape in one read/write operation (except in "variable block size mode"
where it just should be the amount of data actually written in a
single write operation??).
For zftape every read and write access has to be a multiple of a fixed
block size (fixed, but tunable with MTSETBLK ). This block size is a
"tape record" (as mentioned in the GNU mt man page and defaults to
10kb for zftape.
A "file" (in the sense of the mt man page) is a, well, misleading
terminus. What is meant is an area of the tape between two file
marks. This is not a file like a file on the file system, in the sense
that it could have a name, file access modes, could be moved or copied
with cp, mv, rm etc.
Instead, It simply is the area of the tape that was recorded in one
backup session, its end is marked by a tape file mark, and its
beginning is delimited by either BOT or the file mark of the previous
tape "file". That tape "files" are the things that can be skipped with
the MTBSF/FSF commands.
<answer form Claus Heine>
We try to answer the followong questions :
- Is there a good way to erase, as in remove the data or at least the volumes
from a tape, without reformating?
- Can you overwrite the last volume on a tape with making a mess out of it?
- Can you overwrite the last several volumes without making a mess?
- Can you delete the last volume?
If you want to "erase" an entire cartridge, then simply do:
mt -f /dev/qft0 erase
This will erase the volume table (i.e. the "file marks").
Pre-ftape-3.x releases of zftape and ftape used to allow overwriting
of already existing volumes on a cartridge. I have removed this
feature as it was reported that it already has caused data-loss with
some backup programs.
If you indeed need to remove some volumes on the tape then you should
use the
vtblc
program that comes with the ftape-tools package which can be
down-loaded from the same locations as the ftape kernel driver
package. Please refer to the documentation which is contained in the
ftape-tools package for more information.
If you simply want to reuse old tapes, then it suffices to do
mt rewind
If the tape is at BOT (Begin Of Tape) then every write access to the
tape will silently erase all file marks and overwrite the data already
existing on the tape.
<answer by Claus Heine>
Here is as little perl/bash script that lists the contents of a cartridge
using the zftape specific "volinfo" ioctl. Hope this shows how to
handle this kind of stuff.
What it basically does is the following:
- Rewind the cartridge
- Issue the volinfo command:
claus@thales:~$ mt volinfo
file number = 1
block size = 10240
physical space used = 522.0 kilobytes
real size of volume = 520.0 kilobytes
Parse the ouput and place the values in appropriate variables
- Skip to the next volume with "mt fsf"
- Exit if this gives an error (EOD), otherwise "goto 2)"
The Perl Script
#!/usr/bin/perl
#
# Copyright (C) 1997 Claus-Justus Heine
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; see the file COPYING. If not, write to
# the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
#
# This script implements a simple contents listing for the zftape
# package using the MTIOCVOLINFO ioctl.
#
$version = <<EOT;
listtape-1.0 -- a perl script to list the contents of a floppy tape cartridge
under Linux using the zftape driver
RCS \$Revision: 1.2 $
RCS \$Date: 1998/08/30 13:44:03 $
EOT
$tapedev = "/dev/tape";
$usage = <<EOT;
Usage: listtape [options ...]
Mandatory or optional arguments to long options are mandatory or optional
for short options too.
-f, --file=FILE Tape device to use. Default is "/dev/tape".
-h, --help Print this help.
-? Same as '-h'.
--usage Same as '-h'.
-V, --version Print version information.
Author: Claus-Justus Heine <claus\@momo.math.rwth-aachen.de>
EOT
while ($ARGV[0] =~ /^-/) {
$_ = shift;
if (/--file/) {$_ = shift; $tapedev = $_; next;}
if (/-f/) {$_ = shift; $tapedev = $_; next;}
if (/--help/) { print $usage; exit 0; }
if (/-h/) { print $usage; exit 0; }
if (/--usage/) { print $usage; exit 0; }
if (/-\?/) { print $usage; exit 0; }
if (/--version/) { print $version; exit 0; }
if (/-V/) { print $version; exit 0; }
die $usage;
}
&open_tape($tapedev, "status");
while(<FTMT>)
{
$online = 1 if (/.*online.*/);
}
if (! $online) { die "No cartridge present.\n"; }
&mtop($tapedev, "rewind");
printf "%11s%12s%20s%20s\n",
"file number", "block size", "volume size", "tape space";
while (1)
{
&open_tape($tapedev, "volinfo");
while (<FTMT>) {
if (/^file number\s*=\s*([0-9]*)$/) { $filenumber = $1; }
if (/^block size\s*=\s*([0-9]*)$/) { $blocksize = $1; }
if (/^physical space used\s*=\s*([[0-9]*.*)/) { $rawsize = $1; }
if (/^real size of volume\s*=\s*([[0-9]*.*)/) { $size = $1; }
}
close(FTMT);
if (&mtop($tapedev, "fsf 1") != 0) {
&mtop($tapedev,"rewind");
print "\nRemaining space: $rawsize\n";
print "Tape block size: $blocksize\n";
exit 0;
}
printf "%6d %5d %20s%20s\n",
$filenumber, $blocksize, $size, $rawsize;
}
sub mtop
{
local ($tape, $operation) = @_;
local ($exitval);
system "ftmt -f $tape $operation > /dev/null 2>&1";
}
sub open_tape
{
local ($tape, $operation) = @_;
local ($command);
$command = "ftmt -f " . $tape . " " . $operation . " |";
open(FTMT, $command) || die "Couldn't open $command -- $!\n";
}
The Bash Script
#! /bin/bash
#
# Copyright (C) 1997 Claus-Justus Heine
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; see the file COPYING. If not, write to
# the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
#
# This script implements a simple contents listing for the zftape
# package using the MTIOCVOLINFO ioctl.
#
#
# insert better option parsing here
#
TAPEDEV=${1-/dev/tape}
if ! echo $TAPEDEV | grep "/dev/n"
then
TAPEDEV=/dev/n$(basename $TAPEDEV)
fi
if ! [ -c $TAPEDEV ]
then
echo $TAPEDEV is not a character device! 1>&2
exit 1
fi
if ! mt -f $TAPEDEV rewind
then
echo Could not rewind $TAPEDEV - no cartridge present? 1>&2
exit 1
fi
echo -e "\nContents of $TAPEDEV:\n"
printf "%11s%12s%20s%20s\n" "file number" "block size" "volume size" "tape space"
trap "rm -f /tmp/$0.$$" exit
while true
do
if ! foo=$(mt -f $TAPEDEV volinfo |cut -f 2 -d =)
then
echo $TAPEDEV doesn\'t seem to be a floppy tape device 1>&2
exit 1
fi
#
# "echo foo | read foo" will not work as the "read foo" is executed in
# another shell.
#
echo $foo > /tmp/$0.$$
read file blksz used usedunit size sizeunit < /tmp/$0.$$
if ! mt -f $TAPEDEV fsf 1 > /dev/null 2>&1
then
echo -e "\nRemaining space: $used $usedunit"
echo -e "Tape block size: $blksz"
if ! mt -f $TAPEDEV rewind
then
echo Rewind of $TAPEDEV failed 1>&2
exit 1
fi
exit 0
fi
printf "%6d %5d %20s%20s\n"\
$file $blksz "$size $sizeunit" "$used $usedunit"
done
<answer from Claus Heine>
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