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(gzip.info)Tapes

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Using `gzip' on tapes
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   When writing compressed data to a tape, it is generally necessary to
pad the output with zeroes up to a block boundary. When the data is
read and the whole block is passed to `gunzip' for decompression,
`gunzip' detects that there is extra trailing garbage after the
compressed data and emits a warning by default if the garbage contains
nonzero bytes. You have to use the `--quiet' option to suppress the
warning. This option can be set in the `GZIP' environment variable, as
in:

     for sh:    GZIP="-q"  tar -xfz --block-compress /dev/rst0
     for csh:   (setenv GZIP "-q"; tar -xfz --block-compress /dev/rst0)

   In the above example, `gzip' is invoked implicitly by the `-z'
option of GNU `tar'.  Make sure that the same block size (`-b' option
of `tar') is used for reading and writing compressed data on tapes.
(This example assumes you are using the GNU version of `tar'.)