=head1 NAME

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

=head1 SYNOPSIS

 nbdkit ext2 disk=fs.img file=/disks/disk.raw

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

=head1 DESCRIPTION

C<nbdkit-ext2-plugin> is an nbdkit plugin which can read and
write files inside ext2, ext3 or ext4 filesystem images.

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

 nbdkit ext2 disk=fs.img file=/disks/disk.raw

Commonly disk images are partitioned.  In that case you must
use L<nbdkit-partition-filter(1)> to select the partition:

 nbdkit --filter=partition ext2 disk=.. file=.. partition=1

This plugin can both read and write to the file inside the filesystem.
Use the I<-r> flag to force a readonly connection, but note this does
I<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 plugin does I<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 plugin is implemented using the ext2fs library which is provided
in most Linux distros, and also available as part of the e2fsprogs
project.

L<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.

=head1 PARAMETERS

=over 4

=item B<disk=>FILENAME

The ext2, ext3 or ext4 filesystem, a file on the host.

You could also use a device name here if the filesystem is located on
a device.  Be careful that the filesystem is not being accessed in
parallel by another program and is not mounted, as that will almost
certainly result in disk corruption in the filesystem.

The plugin expects a raw filesystem.  If the file/device is
partitioned, use L<nbdkit-partition-filter(1)>.

=item B<file=>PATH

The full path of the file within the filesystem that will be exposed
over NBD.  The path must be absolute (starts with C</>).

=back

=head1 FILES

=over 4

=item F<$plugindir/nbdkit-ext2-plugin.so>

The plugin.

Use C<nbdkit --dump-config> to find the location of C<$plugindir>.

=back

=head1 VERSION

C<nbdkit-ext2-plugin> first appeared in nbdkit 1.4.

=head1 SEE ALSO

L<nbdkit(1)>,
L<nbdkit-plugin(3)>,
L<nbdkit-partition-filter(1)>,
L<nbdkit-guestfs-plugin(1)>,
L<http://e2fsprogs.sourceforge.net/>,
L<fuse2fs(1)>.

=head1 AUTHORS

Richard W.M. Jones

=head1 COPYRIGHT

Copyright (C) 2018 Red Hat Inc.
