2. Preparing VM Images for S²E

To run S²E, you need a QEMU-compatible virtual machine disk image. S²E can run any x86 operating system inside the VM.

Contents

• Preparing VM Images for S²E
  • Fetching a Prepared VM
  • Using an existing VM
  • Installing a new VM
  • Recommendations

There are several ways of getting a VM that can be used with S²E. In this document, we will quickly cover three of them. For more information about managing S²E VMs and how things work underneath, see Managing VMs.

Note: In this document, $S2EDIR denotes the location where all the S²E related files lie in, as explained in Building the S²E Platform. Furthermore, this document makes extensive use of the $S2EDIR/src/ctl script, and runs it simply as the ctl command. You may achieve the same effect by

$ alias ctl=$S2EDIR/src/ctl

or by adding a symbolic link from somewhere in your PATH environment.

2.1. Fetching a Prepared VM

A prepared VM is available on Amazon S3, and can be fetched and imported as follows:

$ wget https://s3.amazonaws.com/chef.dslab.epfl.ch/vm/s2e-base.tar.gz
$ ctl vm import s2e-base.tar.gz MyBox

Once it’s done, the newly imported VM should appear in the list of managed VMs:

$ ctl vm list
MyBox
  Size: 10240.0MiB

2.2. Using an existing VM

If you have already got an existing QEMU-compatible VM, it can be used by S²E if if it has the raw format. For other formats, you will first need to run qemu-img convert on the disk image file, e.g. for files in the qcow2 format:

$ qemu-img convert -f qcow2 -O raw disk.qcow disk.raw

The raw disk image can then be imported with

$ ctl vm import --raw disk.raw MyBox

2.3. Installing a new VM

Note: Any QEMU-compatible VM can be made ready-for-use with S²E, so installing it the classic way with a vanilla QEMU and importing it as seen above is perfectly reasonable. This subsection shows an alternative way to perform the installation with the ctl script.

First, a new virtual machine must be created. This is conveniently done by

$ ctl vm create MyBox 5120M
[ OK ] initialise VM
[ OK ] create 5120MiB image

Next, get an installation CD with the distribution of your choice, e.g.

$ wget http://cdimage.debian.org/debian-cd/7.7.0/i386/iso-cd/debian-7.7.0-i386-CD-1.iso

Now, the previously created VM is started using ctl‘s run command:

$ ctl run -q=-drive -q file=debian-7.7.0-i386-CD-1.iso MyBox kvm
             ↑         ↑
             QEMU options

Once the installation is finished, it is recommended to get some development tools (C/C++ compiler) in the guest machine; in the example of Debian, you’d run

guest$ su -c "apt-get install build-essential"

2.4. Recommendations

• Disable fancy desktop themes. Most OSes have a GUI, which consumes resources. Disabling all visual effects will make program analysis faster.
• Disable the screen saver.
• Disable unnecessary services to save memory and speed up the guest. Services like file sharing, printing, wireless network configuration, or firewall are useless unless you want to test them in S²E.
• Avoid the QEMU virtio network interface for now. In the version of QEMU that is bundled into S²E, there can be random crashes.