[flexbackup-help] Error setting block size

[Steffen S. <s.s...@x-...>]

Hi everybody,
I'am a new in Flexbackup. I tried  to use a IDE tapedrive....but getting 
trouble with my settings.

Error-Message:

flexbackup version 1.0.5 (http://flexbackup.sourceforge.net)
/etc/flexbackup.conf syntax OK

|------------------------------------------------------------
| Checking 'buffer' on this machine... Ok
| Checking /bin/sh on this machine... bash2
|------------------------------------------------------------
| Trying "mt defblksize" instead of "mt setblk"
Error setting block size
Neither of these commands worked:
  mt -f /dev/nst0 setblk 0
  mt -f /dev/nst0 defblksize 0


flexbackup.conf:

# ----------------------------------------------------------------------
# General configuration section

# Archive type?  afio, dump, tar, cpio, star, pax, zip
$type = 'afio';

# List the directories you wish to dump when 'all' is given
# Just a simple space-separated list
# Remote filesystems should denoted as 'host:dir'
#
# Example:
#   $filesystems[0] = '/ /usr /home machine1:/usr machine2:/home';
#
# The array index is a tape number. If you want an 'all' level 0 backup to
# span multiple tapes, add more lines with different array indices. You will
# be prompted for tape change in between.
#
$filesystems[0] = '/home /etc /export';

# Compression
$compress = 'gzip'; # one of false/gzip/bzip2/zip/compress/hardware
$compr_level = '4'; # compression level (1-9) (for gzip/bzip2/zip)

# Buffering
$buffer = 'buffer';   # 'false' or 'buffer', to use buffer program to 
help streaming
$buffer_megs = '3';  # buffer memory size (in megabytes)
$pad_blocks = 'true';

# Device to backup to - non-rewinding version please!
#
# Examples:
#    Linux SCSI: /dev/nst0       Linux IDE: /dev/nht0
#    Linux ftape: /dev/nqft0     FreeBSD SCSI: /dev/nrsa0
#
# If a directory, will archive to files in that directory rather than a 
device
# If "host:/dev/tapedevice", will use remote tape drive via rsh/ssh
#
$device = '/dev/nst0';
#$device = '/root/backup';

# Block size (k) to use
# Default is 10 for most things.  Some tape drives need 32 or 64.
# Set to '0' to disable all blocking
$blksize = '0';

# True to use "variable" block size for the tape device (mt setblk 0)
# If false, will use the $blksize parameter above. All non-mt commands
# will still use $blksize regardless of this value
$mt_var_blksize = 'false';

# Padding.  True to pad blocks to blocksize (devices only, not used when
# archiving to files)
$pad_blocks = 'true';

Is there someone who can tell my how to solve this........ nice 
problem???  ;-))

Thanks
Steffen