nbdkit-ext2-filter(1)

NAME
nbdkit-ext2-filter - read and write files inside ext2, ext3 or ext4 filesystems

SYNOPSIS
 nbdkit --filter=ext2 file fs.img ext2file=/disks/disk.raw

 nbdkit --filter=ext2 --filter=partition file fs.img \
    partition=1 ext2file=exportname

DESCRIPTION
"nbdkit-ext2-filter" is an nbdkit filter which can read and write files inside ext2, ext3 or ext4 filesystem images.

Suppose you have an ext2/3/4 filesystem image called fs.img which contains inside itself a file called disk.raw inside a directory on the filesystem called /disks, then you could serve that file over NBD using:

 nbdkit --filter=ext2 file fs.img ext2file=/disks/disk.raw

Commonly disk images are partitioned. In that case, you must select just the partition of a disk image that contains an ext2 filesystem, by using nbdkit-partition-filter(1):

 nbdkit --filter=ext2 --filter=partition file fs.img \
    partition=1 ext2file=/disks/disk.raw

This filter can both read and write to the file inside the filesystem. Use the -r flag to force a readonly connection, but note this does not guarantee that no writes are made to the filesystem. In particular we may have to replay the ext3 journal in order to open a filesystem even read-only.

The filter does not support multiple parallel connections, because there is a risk of corrupting the filesystem (as if the filesystem was mounted by multiple machines). If a second connection is made to nbdkit, it will block until the first connection closes.

The filter is implemented using the ext2fs library which is provided in most Linux distros, and also available as part of the e2fsprogs project.

nbdkit-guestfs-plugin(1) is a more generic plugin which can read files from all kinds of different filesystem types, even if they are partitioned or use logical volumes. It uses libguestfs instead of e2fsprogs.

PARAMETERS

ext2file=PATH
    The full path of the file within the filesystem that will be exposed over NBD. The path must be absolute (starts with "/").

ext2file=exportname
    The plugin will expose the path within the filesystem chosen by the exportname passed by the client. Note that this mode allows the client to deduce which files exist within the disk image, which may be a security risk in some situations.

    At present, when using this mode, the server does not advertise any particular exports; however, you may use nbdkit-exportname-filter(1) to perform that task. Similarly, the underlying plugin must support the default export name, "".

FILES

$filterdir/nbdkit-ext2-filter.so
    The filter.

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

VERSION
"nbdkit-ext2-filter" first appeared in nbdkit 1.18, replacing "nbdkit-ext2-plugin" which was added in nbdkit 1.4 and removed in nbdkit 1.22.

SEE ALSO
nbdkit(1), nbdkit-plugin(3), nbdkit-exportname-filter(1), nbdkit-partition-filter(1), nbdkit-guestfs-plugin(1), http://e2fsprogs.sourceforge.net/, fuse2fs(1).

AUTHORS
Eric Blake

Richard W.M. Jones

COPYRIGHT
Copyright (C) 2018-2020 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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