vmbetter is a versatile tool for making customized Debian-based environments. It can generate kernel+initramfs pairs, QCOW hard disk images, and ISO CDROM images. This document focuses on the latter, specifically on how you can use vmbetter to easily make a customized LiveCD.
In this article, we'll create a LiveCD which boots you straight into a GUI with Wireshark running--it's just an example, but one that could be useful for someone trying to make a ready-to-deploy security toolkit ala Kali Linux.
Set up vmbetter
To get vmbetter, you'll want to download and compile the minimega repository. First, make sure you have a Go compiler installed. Then, install some libraries needed to build minimega and the associated tools:
# fetch pre-requisites $ sudo apt-get install libpcap-dev syslinux # On ubuntu 16.04lts you need these as well $ sudo apt-get debootstrap genisoimage extlinux
With those installed, you can pull down the minimega repo and build:
# get the repository $ git clone firstname.lastname@example.org:sandia-minimega/minimega.git $ cd minimega $ ./all.bash
There should now be a binary called
vmbetter in the
Making a vmbetter config
vmbetter builds images based on rules specified in a configuration file. It also inserts any additional files you may want into the filesystem of the image it creates.
Write the config file
We'll start by creating our configuration file. From the minimega repository
root, open a new file called
directory contains several other configurations which could be instructive, but
for now just paste the following text into the file and save it:
parents = "default_amd64.conf" packages = "traceroute dnsutils wget tcpdump telnet wireshark xserver-xorg-core xserver-xorg-input-all xserver-xorg-video-fbdev xserver-xorg-video-cirrus xterm xinit blackbox" overlay = "misc/vmbetter_configs/wireshark_overlay" postbuild = ` sed -i 's/nullok_secure/nullok/' /etc/pam.d/common-auth sed -i 's/PermitRootLogin without-password/PermitRootLogin yes/' /etc/ssh/sshd_config sed -i 's/PermitEmptyPasswords no/PermitEmptyPasswords yes/' /etc/ssh/sshd_config passwd -d root `
The configuration file specifies several important options: one or more parent configs, a list of packages to install, the "overlay" directory, and the "postbuild" commands. The overlay directory contains any files you want to add to the disc's filesystem. The postbuild commands are a list of shell commands to be run as the final step of the building process; we use it here to set up passwordless root login for convenience.
wireshark.conf has a parent configuration,
That file contains some very basic packages which you'll want in almost every
case, so most configurations will want to either include
as a parent, or set their parent to another configuration which uses
default_amd64.conf as its parent.
You'll see that we install Wireshark, the basic X.org packages, and some bare minimum X utilities: xterm, xinit, blackbox. If you want additional programs, you can add their package names to the list. vmbetter will automatically figure out any dependencies they may have and install them for you.
Populate the overlay filesystem
Our configuration file says we're going to put any additional files we want
misc/vmbetter_configs/wireshark_overlay. This directory contains a
hierarchy of files and directories, based at /, that we want copied into the
image we build. Let's start by copying over an existing overlay to get a
$ cp -r misc/vmbetter_configs/default_overlay misc/vmbetter_configs/wireshark_overlay
If you look in that directory, you'll see a few basic files in a hierarchy:
$ du -a misc/vmbetter_configs/wireshark_overlay/ 4 misc/vmbetter_configs/wireshark_overlay/init 8 misc/vmbetter_configs/wireshark_overlay/
In order to make the LiveCD automatically launch X and Wireshark as soon as we log in as root, we can set up a few configuration files:
$ cd misc/vmbetter_configs/wireshark_overlay $ mkdir -p root $ cat > root/.profile << EOF #!/bin/sh xinit -- /usr/bin/Xorg & EOF $ cat > root/.xinitrc << EOF #!/bin/sh wireshark & exec blackbox EOF $ cd ../../.. # go back to the root of the minimega repo # On ubuntu init may not have proper permissions $ chmod 777 misc/vmbetter_conf/wireshark_overlay/init
.profile launches X automatically as soon as root logs in, and then
.xinitrc starts Wireshark and the Blackbox window manager once X starts.
Build the image
Now that we've specified how to build the image, we can fire up vmbetter and actually build it. Here's the command I used to build:
$ sudo ./bin/vmbetter -branch stable -iso -level debug -mbr /usr/lib/syslinux/mbr/mbr.bin misc/vmbetter_configs/wireshark.conf
It's rather complex, so I'll break down each part:
-branch stable: specifies that vmbetter should use the Debian stable branch to build
-iso: specifies that we want an ISO image
-level debug: specifies that we want lots of debug output
-mbr /usr/lib/syslinux/mbr/mbr.bin: On Debian Unstable, the
syslinuxpackage puts the
mbr.binfile in a different place than expected by vmbetter
misc/vmbetter_configs/wireshark.conf: the path to the configuration file
(Depending on your system, you may not need to specify the
-mbr flag, or you
may find that
mbr.bin is in yet a different location.)
When you run vmbetter, it will print lots of debugging information as it
calculates dependencies, fetches packages (this will take a long time),
installs the packages in a temporary environment, and finally creates an ISO
image. If all goes well, you should end up with a file called
in the current directory
Test the image
If everything worked right, you should have a file called
the current directory. We can test it using minimega:
$ sudo ./bin/minimega minimega$ vm config cdrom wireshark.iso minimega$ vm launch kvm wireshark minimega$ vm start wireshark
Start miniweb and then point your web browser to http://localhost:9001, you should be able to see minimega's web front-end. There should be one VM listed on the main page; click the screenshot to open a VNC session to it.
Once you're in the VNC session, you will probably see a login prompt. Log in as
root, no password necessary. As soon as you log in, it should start up X, run
the window manager, and start up Wireshark.
If you want to run the image on real computers, simply burn
a CD and use it to boot.