virt-win-reg - Export and merge Windows Registry entries from a Windows
virt-win-reg domname 'HKLM\Path\To\Subkey'
virt-win-reg domname 'HKLM\Path\To\Subkey' name
virt-win-reg domname 'HKLM\Path\To\Subkey' @
virt-win-reg --merge domname [input.reg ...]
virt-win-reg [--options] disk.img ... # instead of domname
You must not use "virt-win-reg" with the --merge option on live virtual
machines. If you do this, you will get irreversible disk corruption in
the VM. "virt-win-reg" tries to stop you from doing this, but doesn't
catch all cases.
Modifying the Windows Registry is an inherently risky operation. The
format is deliberately obscure and undocumented, and Registry changes
can leave the system unbootable. Therefore when using the --merge
option, make sure you have a reliable backup first.
This program can export and merge Windows Registry entries from a
The first parameter is the libvirt guest name or the raw disk image of
a Windows guest.
If --merge is not specified, then the chosen registry key is
displayed/exported (recursively). For example:
$ virt-win-reg Windows7 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft'
You can also display single values from within registry keys, for
$ cvkey='HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion'
$ virt-win-reg Windows7 $cvkey ProductName
Windows 7 Enterprise
With --merge, you can merge a textual regedit file into the Windows
$ virt-win-reg --merge Windows7 changes.reg
This program is only meant for simple access to the registry. If you
want to do complicated things with the registry, we suggest you
download the Registry hive files from the guest using libguestfs(3) or
guestfish(1) and access them locally, eg. using hivex(3), hivexsh(1) or
Display brief help.
Display version number and exit.
Enable debugging messages.
If using libvirt, connect to the given URI. If omitted, then we
connect to the default libvirt hypervisor.
If you specify guest block devices directly, then libvirt is not
used at all.
Specify the format of disk images given on the command line. If
this is omitted then the format is autodetected from the content of
the disk image.
If disk images are requested from libvirt, then this program asks
libvirt for this information. In this case, the value of the
format parameter is ignored.
If working with untrusted raw-format guest disk images, you should
ensure the format is always specified.
In merge mode, this merges a textual regedit file into the Windows
Registry of the virtual machine. If this flag is not given then
virt-win-reg displays or exports Registry entries instead.
Note that --merge is unsafe to use on live virtual machines, and
will result in disk corruption. However exporting (without this
flag) is always safe.
When merging (only), you may need to specify the encoding for
strings to be used in the hive file. This is explained in detail
in "ENCODING STRINGS" in Win::Hivex::Regedit(3).
The default is to use UTF-16LE, which should work with recent
versions of Windows.
When exporting (only), assume strings are UTF-16LE and print them
as strings instead of hex sequences. Remove the final zero
codepoint from strings if present.
This is unsafe and does not preserve the fidelity of strings in the
original Registry for various reasons:
· Assumes the original encoding is UTF-16LE. ASCII strings and
strings in other encodings will be corrupted by this
· Assumes that everything which has type 1 or 2 is really a
string and that everything else is not a string, but the type
field in real Registries is not reliable.
· Loses information about whether a zero codepoint followed the
string in the Registry or not.
This all happens because the Registry itself contains no
information about how strings are encoded (see "ENCODING STRINGS"
You should only use this option for quick hacking and debugging of
the Registry contents, and never use it if the output is going to
be passed into another program or stored in another Registry.
The program currently supports Windows NT-derived guests starting with
Windows XP through to at least Windows 8.
The following Registry keys are supported:
where SID is a Windows User SID (eg. "S-1-5-18").
where username is a local user name (this is a libguestfs
You can use "HKLM" as a shorthand for "HKEY_LOCAL_MACHINE", and "HKU"
The literal keys "HKEY_USERS\$SID" and "HKEY_CURRENT_USER" are not
supported (there is no "current user").
Windows 8 "fast startup" can prevent virt-win-reg from being able to
edit the Registry. See "WINDOWS HIBERNATION AND WINDOWS 8 FAST
STARTUP" in guestfs(3).
"virt-win-reg" expects that regedit files have already been reencoded
in the local encoding. Usually on Linux hosts, this means UTF-8 with
Unix-style line endings. Since Windows regedit files are often in
UTF-16LE with Windows-style line endings, you may need to reencode the
whole file before or after processing.
To reencode a file from Windows format to Linux (before processing it
with the --merge option), you would do something like this:
iconv -f utf-16le -t utf-8 < win.reg | dos2unix > linux.reg
To go in the opposite direction, after exporting and before sending the
file to a Windows user, do something like this:
unix2dos linux.reg | iconv -f utf-8 -t utf-16le > win.reg
For more information about encoding, see Win::Hivex::Regedit(3).
If you are unsure about the current encoding, use the file(1) command.
Recent versions of Windows regedit.exe produce a UTF-16LE file with
Windows-style (CRLF) line endings, like this:
$ file software.reg
software.reg: Little-endian UTF-16 Unicode text, with very long lines,
with CRLF line terminators
This file would need conversion before you could --merge it.
Registry keys like "CurrentControlSet" don't really exist in the
Windows Registry at the level of the hive file, and therefore you
cannot modify these.
"CurrentControlSet" is usually an alias for "ControlSet001". In some
circumstances it might refer to another control set. The way to find
out is to look at the "HKLM\SYSTEM\Select" key:
# virt-win-reg WindowsGuest 'HKLM\SYSTEM\Select'
"Current" is the one which Windows will choose when it boots.
Similarly, other "Current..." keys in the path may need to be replaced.
DELETING REGISTRY KEYS AND VALUES
To delete a whole registry key, use the syntax:
To delete a single value within a key, use the syntax:
Note that some of these tips modify the guest disk image. The guest
must be shut off, else you will get disk corruption.
RUNNING A BATCH SCRIPT WHEN A USER LOGS IN
Prepare a DOS batch script, VBScript or executable. Upload this using
guestfish(1). For this example the script is called "test.bat" and it
is uploaded into "C:\":
guestfish -i -d WindowsGuest upload test.bat /test.bat
Prepare a regedit file containing the registry change:
cat > test.reg <<'EOF'
In this example we use the key "RunOnce" which means that the script
will run precisely once when the first user logs in. If you want it to
run every time a user logs in, replace "RunOnce" with "Run".
Now update the registry:
virt-win-reg --merge WindowsGuest test.reg
INSTALLING A SERVICE
This section assumes you are familiar with Windows services, and you
either have a program which handles the Windows Service Control
Protocol directly or you want to run any program using a service
wrapper like SrvAny or the free RHSrvAny.
First upload the program and optionally the service wrapper. In this
case the test program is called "test.exe" and we are using the
guestfish -i -d WindowsGuest <<EOF
upload rhsrvany.exe /rhsrvany.exe
upload test.exe /test.exe
Prepare a regedit file containing the registry changes. In this
example, the first registry change is needed for the service itself or
the service wrapper (if used). The second registry change is only
needed because I am using the RHSrvAny service wrapper.
cat > service.reg <<'EOF'
· For use of "ControlSet001" see the section above in this manual
page. You may need to adjust this according to the control set
that is in use by the guest.
· "ObjectName" controls the privileges that the service will have.
An alternative is "ObjectName"="LocalSystem" which would be the
most privileged account.
· For the meaning of the magic numbers, see this Microsoft KB
Update the registry:
virt-win-reg --merge WindowsGuest service.reg
Be careful when passing parameters containing "\" (backslash) in the
shell. Usually you will have to use 'single quotes' or double
backslashes (but not both) to protect them from the shell.
Paths and value names are case-insensitive.
Libvirt guest names can contain arbitrary characters, some of which
have meaning to the shell such as "#" and space. You may need to quote
or escape these characters on the command line. See the shell manual
page sh(1) for details.
hivex(3), hivexsh(1), hivexregedit(1), guestfs(3), guestfish(1),
virt-cat(1), Sys::Guestfs(3), Win::Hivex(3), Win::Hivex::Regedit(3),
Richard W.M. Jones http://people.redhat.com/~rjones/
Copyright (C) 2010 Red Hat Inc.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
To get a list of bugs against libguestfs, use this link:
To report a new bug against libguestfs, use this link:
When reporting a bug, please supply:
· The version of libguestfs.
· Where you got libguestfs (eg. which Linux distro, compiled from
· Describe the bug accurately and give a way to reproduce it.
· Run libguestfs-test-tool(1) and paste the complete, unedited output
into the bug report.