qemu


Install Gnome Boxes on Kali Linux

Our solution in getting Gnome Boxes to work on Kali Linux (which is a Debian-derived Linux distribution just like Ubuntu) is the following:

First install Gnome Boxes along with all needed virtualization software:

sudo apt-get install -y gnome-boxes qemu-kvm libvirt0 virt-manager bridge-utils;

Then, edit the file /etc/libvirt/qemu.conf to uncomment the following line:

#user = "root"

Finally, restart the host machine and your Gnome Boxes will be ready to use.

Long story

Recently, we were setting up a Kali Linux machine and one of the requirements was to add virtualization support so that the user could execute virtual machines doing.. other stuff. We started by installing gnome-boxes only (hoping that would be enough)

sudo apt-get install -y gnome-boxes;

.. but we got an error:

Boxes cannot access the virtualization backend

Apparently, installing gnome-boxes only, the dependency system did not automatically assume we would need to install an engine to handle the virtual machines, so we had to install the following as well:

sudo apt-get install -y qemu-kvm libvirt0 virt-manager bridge-utils;

After the installation, we tried  to create a new virtual machine but it would fail when we tried to start it. After looking into the logs we found the following useful information:

State: GVIR_DOMAIN_STATE_SHUTOFF

It seems that our user (even if it was root) could not start the QEMU process. To fix this issue we had to modify the file /etc/libvirt/qemu.conf and uncomment the following line:

#user = "root"

from this section

# The user for QEMU processes run by the system instance. It can be
# specified as a user name or as a user id. The qemu driver will try to
# parse this value first as a name and then, if the name doesn't exist,
# as a user id.
#
# Since a sequence of digits is a valid user name, a leading plus sign
# can be used to ensure that a user id will not be interpreted as a user
# name.
#
# Some examples of valid values are:
#
# user = "qemu" # A user named "qemu"
# user = "+0" # Super user (uid=0)
# user = "100" # A user named "100" or a user with uid=100
#
#user = "root"

# The group for QEMU processes run by the system instance. It can be
# specified in a similar way to user.
#group = "root"

After doing this change and restarting the host machine we were able to start and use any virtual machine in Gnome Boxes.

Extra information

In this case, we were using Kali Linux, where people usually operate it using the root account only.
On other installations, like on an Ubuntu installation you would need to handle differently the last step that requires you to edit the /etc/libvirt/qemu.conf file.

Specifically, the best way to handle this issue on a multi-user environment (like Ubuntu) would be to replace the following line:

#group = "root"

with this

group = "kvm"

and then add yourself to the kvm group before restarting the host machine

sudo usermod -a -G kvm $USER;

Doing so, it allows you to enable access to the virtualization services to multiple users of you choice instead of limiting it to one account.


Fedora Configure Hardware Acceleration for the Android Emulator

While setting up Android Studio on a Fedora 27 x64, we got the following message from the Android Studio Setup Wizard:

We have detected that your system can run the Android emulator in an accelerated performance mode.
Linux-based systems support virtual machine acceleration through the KVM (Kernel-mode Virtual Machine) software package.

Search for install instructions for your particular Linux configuration (Android KVM Linux Installation) that KVM is enabled for faster Android emulator performance.

After going through the website mentioned in the message we noticed that there were no instructions for Fedora so we decided to write our own.

Below are the steps we followed to enable hardware acceleration for the Android emulator.

Step 1: Verify that your CPU has virtualization extensions.

Execute the following in a terminal:

egrep '^flags.*(vmx|svm)' /proc/cpuinfo;

if you get ANY output then it would mean that your CPU supports either VMX or SVM which is good.
If it does not print anything then the emulator will fall back to software virtualization, which is extremely slow.

Step 2: Install the virtualization packages

sudo dnf group install --with-optional virtualization;

Step 3: Start the service

sudo systemctl start libvirtd;

Step 4: Automatically start the service on boot:

sudo systemctl enable libvirtd;

Step 5: Verify that the kvm kernel modules were loaded

lsmod | grep kvm

If the above command does not print kvm_intel or kvm_amd, it would mean that KVM is not properly configured.


Send ALT+CTRL+Delete to QEMU virtual machine 1

Recently we wanted to start a Windows virtual machine from a physical hard disk using a Fedora w/ GNOME 3 host machine to change the domain password of a user.
To do so, we used QEMU, QEMU is a generic and open source machine emulator and virtualizer.

To perform the password change, we needed to sent the ALT+CTRL+Delete key combination to the virtual machine to access the system screen and then change the user password.
Pressing ALT+CTRL+Delete on the Fedora/GNOME 3 host machine, it popped up a prompt to shut down the host machine instead of sending the key combination to the active window of the VM. Apparently, we could not sent the key combination directly to the VM and had to find a way around it.

Solution:

We pressed ALT+CTRL+2 while the QEMU window was selected/active to switch to the QEMU terminal/monitor.
In the blank screen that appeared, we typed sendkey alt-ctrl-delete and pressed the Enter key.
This action sent to the virtual machine OS the key combination ALT+CTRL+Delete.
Finally, to switch back  to the guest screen we pressed ALT+CTRL+1.


Fedora: Start a Virtual Machine using a physical hard disk

Recently, we wanted to start a Virtual Machine running a Windows installation from a physical hard disk.

We could not find a way for GNOME Boxes to achieve this, so we installed qemu to do so.

We installed qemu using:

sudo dnf install qemu -y;

Configuring our command to start the Virtual Machine from the physical hard drive:

  • Our hard disk was identified on the physical machine as /dev/sda so we set the -hda parameter to that value.
  • Then we added the parameter -boot c to instruct the virtual machine to boot from the first hard disk.
  • The default guest start-up RAM size was 128 MiB, so we set the parameter -m to 4096 to give to the virtual machine 4GB of RAM.
  • Finally we added the -snapshot parameter which instructed the system to write to temporary files instead of the disk image files (all disk images are considered as read only).
    In this case, the raw disk image used are not written back. When sectors are written, they are written in a temporary file created in /tmp.
    You can however force the write back to the raw disk images by using the commit monitor command (or C-a s in the serial console).

In the end our command was as follows:

sudo qemu-kvm -snapshot -m 4096 -boot c -hda /dev/sda;