NAME

       nbdkit-tar-plugin - read and write files inside tar files without unpacking

SYNOPSIS

        nbdkit tar [tar=]FILENAME.tar file=PATH_INSIDE_TAR

DEPRECATED

       The tar plugin is deprecated in nbdkit ≥ 1.22 and will be removed in nbdkit 1.26.  It has
       been replaced with a filter with the same functionality, see nbdkit-tar-filter(1).  You
       can use the filter like this:

        nbdkit file FILENAME.tar --filter=tar tar-entry=PATH_INSIDE_TAR

EXAMPLES

   Serve a single file inside a tarball
        nbdkit tar file.tar file=some/disk.img
        guestfish --format=raw -a nbd://localhost

   Opening a disk image inside an OVA file
       The popular "Open Virtual Appliance" (OVA) format is really an uncompressed tar file
       containing (usually) VMDK-format files, so you could access one file in an OVA like this:

        $ tar tf rhel.ova
        rhel.ovf
        rhel-disk1.vmdk
        rhel.mf
        $ nbdkit -r tar rhel.ova file=rhel-disk1.vmdk
        $ guestfish --ro --format=vmdk -a nbd://localhost

       In this case the tarball is opened readonly (-r option).  The plugin supports write
       access, but writing to the VMDK file in the tarball does not change data checksums stored
       in other files (the "rhel.mf" file in this example), and as these will become incorrect
       you probably won't be able to open the file with another tool afterwards.

DESCRIPTION

       "nbdkit-tar-plugin" is a plugin which can read and writes files inside an uncompressed tar
       file without unpacking the tar file.

       The "tar" and "file" parameters are required, specifying the name of the uncompressed tar
       file and the exact path of the file within the tar file to access as a disk image.

       This plugin will not work on compressed tar files.

       Use the nbdkit -r flag to open the file readonly.  This is the safest option because it
       guarantees that the tar file will not be modified.  Without -r writes will modify the tar
       file.

       The disk image cannot be resized.

PARAMETERS

       [tar=]FILENAME.tar
           The path of the tarball.  This parameter is required.

           "tar=" is a magic config key and may be omitted in most cases.  See "Magic parameters"
           in nbdkit(1).

       file=PATH_INSIDE_TAR
           The path of the file inside the tarball to serve.  This parameter is required.  It
           must exactly match the name stored in the tarball, so use "tar tf filename.tar"

NOTE

   Alternatives to the tar plugin
       The tar plugin ought to be a filter so that you can extract files from within tarballs
       hosted elsewhere (eg. using nbdkit-curl-plugin(1)).  However this is hard to implement
       given the way that the tar(1) command works.

       Nevertheless you can apply the same technique even to tarballs hosted remotely, provided
       you can run tar(1) on them first.  The trick is to use the "tar -tRvf" options to find the
       block number of the file of interest.  In tar files, blocks are 512 bytes in size, and
       there is one hidden block used for the header, so you have to take the block number, add
       1, and multiply by 512.

       For example:

        $ tar -tRvf disk.tar
        block 2: -rw-r--r-- rjones/rjones 105923072 2020-03-28 20:34 disk
        └──┬──┘                           └───┬───┘
        offset = (2+1)*512 = 1536           range

       You can then apply the offset filter:

        nbdkit --filter=offset \
                 curl https://example.com/disk.tar \
                      offset=1536 range=105923072

       If the remote file is compressed then add nbdkit-xz-filter(1):

        nbdkit --filter=offset --filter=xz \
                 curl https://example.com/disk.tar.xz \
                      offset=1536 range=105923072

VERSION

       "nbdkit-tar-plugin" first appeared in nbdkit 1.2.

SEE ALSO

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

AUTHORS

       Richard W.M. Jones.

       Based on the virt-v2v OVA importer written by Tomáš Golembiovský.

COPYRIGHT

       Copyright (C) 2017-2020 Red Hat Inc.

LICENSE

       Redistribution and use in source and binary forms, with or without modification, are
       permitted provided that the following conditions are met:

       •   Redistributions of source code must retain the above copyright notice, this list of
           conditions and the following disclaimer.

       •   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.

       •   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.

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