=head1 NAME

virt-cat - Display files in a virtual machine

=head1 SYNOPSIS

 virt-cat [--options] -d domname file [file ...]

 virt-cat [--options] -a disk.img [-a disk.img ...] file [file ...]

Old-style:

 virt-cat domname file

 virt-cat disk.img file

=head1 DESCRIPTION

C<virt-cat> is a command line tool to display the contents of C<file>
where C<file> exists in the named virtual machine (or disk image).

Multiple filenames can be given, in which case they are concatenated
together.  Each filename must be a full path, starting at the root
directory (starting with '/').

C<virt-cat> can be used to quickly view a file.  To edit a file, use
C<virt-edit>.  For more complex cases you should look at the
L<guestfish(1)> tool (see L</USING GUESTFISH> below).

=head1 EXAMPLES

Display F</etc/fstab> file from inside the libvirt VM called
C<mydomain>:

 virt-cat -d mydomain /etc/fstab

Find out what packages were recently installed:

 virt-cat -d mydomain /var/log/yum.log | tail

Find out who is logged on inside a virtual machine:

 virt-cat -d mydomain /var/run/utmp > /tmp/utmp
 who /tmp/utmp

or who was logged on:

 virt-cat -d mydomain /var/log/wtmp > /tmp/wtmp
 last -f /tmp/wtmp

=head1 OPTIONS

=over 4

=item B<--help>

Display brief help.

=item B<-a> file

=item B<--add> file

Add I<file> which should be a disk image from a virtual machine.  If
the virtual machine has multiple block devices, you must supply all of
them with separate I<-a> options.

The format of the disk image is auto-detected.  To override this and
force a particular format use the I<--format=..> option.

=item B<-a URI>

=item B<--add URI>

Add a remote disk.  See L<guestfish(1)/ADDING REMOTE STORAGE>.

__INCLUDE:blocksize-option.pod__

=item B<-c> URI

=item B<--connect> URI

If using libvirt, connect to the given I<URI>.  If omitted, then we
connect to the default libvirt hypervisor.

If you specify guest block devices directly (I<-a>), then libvirt is
not used at all.

=item B<-d> guest

=item B<--domain> guest

Add all the disks from the named libvirt guest.  Domain UUIDs can be
used instead of names.

=item B<--echo-keys>

When prompting for keys and passphrases, virt-cat normally turns
echoing off so you cannot see what you are typing.  If you are not
worried about Tempest attacks and there is no one else in the room you
can specify this flag to see what you are typing.

=item B<--format=raw|qcow2|..>

=item B<--format>

The default for the I<-a> option is to auto-detect the format of the
disk image.  Using this forces the disk format for I<-a> options which
follow on the command line.  Using I<--format> with no argument
switches back to auto-detection for subsequent I<-a> options.

For example:

 virt-cat --format=raw -a disk.img file

forces raw format (no auto-detection) for F<disk.img>.

 virt-cat --format=raw -a disk.img --format -a another.img file

forces raw format (no auto-detection) for F<disk.img> and reverts to
auto-detection for F<another.img>.

If you have untrusted raw-format guest disk images, you should use
this option to specify the disk format.  This avoids a possible
security problem with malicious guests (CVE-2010-3851).

__INCLUDE:key-option.pod__

__INCLUDE:keys-from-stdin-option.pod__

=item B<-m> dev[:mountpoint[:options[:fstype]]]

=item B<--mount> dev[:mountpoint[:options[:fstype]]]

Mount the named partition or logical volume on the given mountpoint.

If the mountpoint is omitted, it defaults to F</>.

Specifying any mountpoint disables the inspection of the guest and
the mount of its root and all of its mountpoints, so make sure
to mount all the mountpoints needed to work with the filenames
given as arguments.

If you don’t know what filesystems a disk image contains, you can
either run guestfish without this option, then list the partitions,
filesystems and LVs available (see L</list-partitions>,
L</list-filesystems> and L</lvs> commands), or you can use the
L<virt-filesystems(1)> program.

The third (and rarely used) part of the mount parameter is the list of
mount options used to mount the underlying filesystem.  If this is not
given, then the mount options are either the empty string or C<ro>
(the latter if the I<--ro> flag is used).  By specifying the mount
options, you override this default choice.  Probably the only time you
would use this is to enable ACLs and/or extended attributes if the
filesystem can support them:

 -m /dev/sda1:/:acl,user_xattr

Using this flag is equivalent to using the C<mount-options> command.

The fourth part of the parameter is the filesystem driver to use, such
as C<ext3> or C<ntfs>. This is rarely needed, but can be useful if
multiple drivers are valid for a filesystem (eg: C<ext2> and C<ext3>),
or if libguestfs misidentifies a filesystem.

=item B<-v>

=item B<--verbose>

Enable verbose messages for debugging.

=item B<-V>

=item B<--version>

Display version number and exit.

=item B<-x>

Enable tracing of libguestfs API calls.

=back

=head1 OLD-STYLE COMMAND LINE ARGUMENTS

Previous versions of virt-cat allowed you to write either:

 virt-cat disk.img [disk.img ...] file

or

 virt-cat guestname file

whereas in this version you should use I<-a> or I<-d> respectively
to avoid the confusing case where a disk image might have the same
name as a guest.

For compatibility the old style is still supported.

=head1 LOG FILES

To list out the log files from guests, see the related tool
L<virt-log(1)>.  It understands binary log formats such as the systemd
journal.

To follow (tail) text log files, use L<virt-tail(1)>.

=head1 WINDOWS PATHS

C<virt-cat> has a limited ability to understand Windows drive letters
and paths (eg. F<E:\foo\bar.txt>).

If and only if the guest is running Windows then:

=over 4

=item *

Drive letter prefixes like C<C:> are resolved against the
Windows Registry to the correct filesystem.

=item *

Any backslash (C<\>) characters in the path are replaced
with forward slashes so that libguestfs can process it.

=item *

The path is resolved case insensitively to locate the file
that should be displayed.

=back

There are some known shortcomings:

=over 4

=item *

Some NTFS symbolic links may not be followed correctly.

=item *

NTFS junction points that cross filesystems are not followed.

=back

=head1 USING GUESTFISH

L<guestfish(1)> is a more powerful, lower level tool which you can use
when C<virt-cat> doesn't work.

Using C<virt-cat> is approximately equivalent to doing:

 guestfish --ro -i -d domname download file -

where C<domname> is the name of the libvirt guest, and C<file> is the
full path to the file.  Note the final C<-> (meaning "output to
stdout").

The command above uses libguestfs’s guest inspection feature and so
does not work on guests that libguestfs cannot inspect, or on things
like arbitrary disk images that don't contain guests.  To display a
file from a disk image directly, use:

 guestfish --ro -a disk.img -m /dev/sda1 download file -

where F<disk.img> is the disk image, F</dev/sda1> is the filesystem
within the disk image, and C<file> is the full path to the file.

=head1 EXIT STATUS

This program returns 0 if successful, or non-zero if there was an
error.

=head1 SEE ALSO

L<guestfs(3)>,
L<guestfish(1)>,
L<virt-copy-out(1)>,
L<virt-edit(1)>,
L<virt-log(1)>,
L<virt-tail(1)>,
L<virt-tar-out(1)>,
L<http://libguestfs.org/>.

=head1 AUTHOR

Richard W.M. Jones L<http://people.redhat.com/~rjones/>

=head1 COPYRIGHT

Copyright (C) 2010-2023 Red Hat Inc.
