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.IX Title "nbdkit-gzip-filter 1"
.TH nbdkit-gzip-filter 1 2026-04-25 nbdkit-1.47.8 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
nbdkit\-gzip\-filter \- decompress a .gz file
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit file \-\-filter=gzip FILENAME.gz
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit\-gzip\-filter\*(C'\fR is a filter for \fBnbdkit\fR\|(1) which transparently
decompresses a gzip\-compressed file.  You can place this filter on top
of \fBnbdkit\-file\-plugin\fR\|(1) to decompress a local \fI.gz\fR file, or on
top of other plugins such as \fBnbdkit\-curl\-plugin\fR\|(1):
.PP
.Vb 1
\& nbdkit curl \-\-filter=gzip https://example.com/disk.gz
.Ve
.PP
With \fBnbdkit\-tar\-filter\fR\|(1) it can be used to extract files from a
compressed tar file:
.PP
.Vb 2
\& nbdkit curl \-\-filter=tar \-\-filter=gzip \e
\&        https://example.com/file.tar.gz tar\-entry=disk.img
.Ve
.PP
The filter only allows read\-only connections.
.PP
\&\fBNote\fR that gzip files are not very good for random access in large
files because seeking to a position in the gzip file involves
decompressing all data before that point in the file.
\&\fBnbdkit\-indexed\-gzip\-filter\fR\|(1) is an alternate filter to this one
which builds an index file, which can mitigate this problem.  Another
method to compress large disk images is to use \fBxz\fR\|(1) or
\&\fBplzip\fR\|(1).  Both \fBnbdkit\-xz\-filter\fR\|(1) and \fBnbdkit\-lzip\-filter\fR\|(1)
support block\-level decompression if the file was compressed using the
right options.
.PP
To allow seeking this filter has to keep the contents of the complete
uncompressed file, which it does in a hidden temporary file under
\&\f(CW$TMPDIR\fR.
.SH PARAMETERS
.IX Header "PARAMETERS"
There are no parameters specific to this plugin.
.SH "ENVIRONMENT VARIABLES"
.IX Header "ENVIRONMENT VARIABLES"
.ie n .IP """TMPDIR""" 4
.el .IP \f(CWTMPDIR\fR 4
.IX Item "TMPDIR"
Because the gzip format is not seekable, this filter has to store the
complete contents of the compressed file in a temporary file located
in \fI/var/tmp\fR by default.  You can override this location by setting
the \f(CW\*(C`TMPDIR\*(C'\fR environment variable before starting nbdkit.
.SH FILES
.IX Header "FILES"
.ie n .IP \fR\fI$filterdir\fR\fI/nbdkit\-gzip\-filter.so\fR 4
.el .IP \fR\f(CI$filterdir\fR\fI/nbdkit\-gzip\-filter.so\fR 4
.IX Item "$filterdir/nbdkit-gzip-filter.so"
The plugin.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$filterdir\fR.
.SH VERSION
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-gzip\-filter\*(C'\fR first appeared in nbdkit 1.22.  It is derived
from \f(CW\*(C`nbdkit\-gzip\-plugin\*(C'\fR which first appeared in nbdkit 1.0.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\-bzip2\-filter\fR\|(1),
\&\fBnbdkit\-curl\-plugin\fR\|(1),
\&\fBnbdkit\-file\-plugin\fR\|(1),
\&\fBnbdkit\-indexed\-gzip\-filter\fR\|(1),
\&\fBnbdkit\-lzip\-filter\fR\|(1),
\&\fBnbdkit\-tar\-filter\fR\|(1),
\&\fBnbdkit\-xz\-filter\fR\|(1),
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-plugin\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS \*(Aq\*(AqAS IS\*(Aq\*(Aq AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
