nbdkit-gzip-filter - decompress a .gz file
nbdkit file --filter=gzip FILENAME.gznbdkit-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.gzWith 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.imgThe 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 xz(1) or plzip(1). Both nbdkit-xz-filter(1) and nbdkit-lzip-filter(1) support block-level decompression if the file was compressed using the right options.
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.
TMPDIRBecause 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.
The plugin.
Use nbdkit --dump-config to find the location of $filterdir.
nbdkit-gzip-filter first appeared in nbdkit 1.22. It is derived from nbdkit-gzip-plugin which first appeared in nbdkit 1.0.
nbdkit-bzip2-filter(1), nbdkit-curl-plugin(1), nbdkit-file-plugin(1), nbdkit-lzip-filter(1), nbdkit-tar-filter(1), nbdkit-xz-filter(1), nbdkit(1), nbdkit-plugin(3).
Richard W.M. Jones
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