DOKK / manpages / debian 11 / nbdkit / nbdkit-gzip-filter.1.en
nbdkit-gzip-filter(1) NBDKIT nbdkit-gzip-filter(1)

nbdkit-gzip-filter - decompress a .gz file

 nbdkit file --filter=gzip FILENAME.gz

"nbdkit-gzip-filter" is a filter for nbdkit(1) which transparently decompresses a gzip-compressed file. You can place this filter on top of nbdkit-file-plugin(1) to decompress a local .gz file, or on top of other plugins such as nbdkit-curl-plugin(1):

 nbdkit curl --filter=gzip https://example.com/disk.gz

With nbdkit-tar-filter(1) it can be used to extract files from a compressed tar file:

 nbdkit curl --filter=tar --filter=gzip \
        https://example.com/file.tar.gz tar-entry=disk.img

The filter only allows read-only connections.

Note 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. A more practical method to compress large disk images is to use the xz(1) format and nbdkit-xz-filter(1).

To allow seeking this filter has to keep the contents of the complete uncompressed file, which it does in a hidden temporary file under $TMPDIR.

There are no parameters specific to this plugin.

"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 /var/tmp by default. You can override this location by setting the "TMPDIR" environment variable before starting nbdkit.

$plugindir/nbdkit-gzip-plugin.so
The plugin.

Use "nbdkit --dump-config" to find the location of $plugindir.

"nbdkit-gzip-filter" first appeared in nbdkit 1.22. It is derived from "nbdkit-gzip-plugin" which first appeared in nbdkit 1.0.

nbdkit-curl-plugin(1), nbdkit-file-plugin(1), nbdkit-tar-filter(1), nbdkit-xz-filter(1), nbdkit(1), nbdkit-plugin(3).

Richard W.M. Jones

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2021-01-20 nbdkit-1.24.1