In this post I will create a Qemu image and work with it remotely using ssh login.
1. Download and install qemu
If you are having Debian based distro, ubuntu may be, then you can install qemu using the command
sudo apt-get install qemu-system
this will install all qemu-system binaries for all major cpu architectures. If you are having RPM based distro(like fedora etc.), first login as root and type
yum install qemu
else you can also compile the latest stable source. Please refer the README for compilation instructions.
2. Creating and installing image
We need to first create a raw qemu image using command
qemu-img create -f raw IMAGE_NAME.img SIZE
for example, if I want to create an image of
32G with name as
qemu-img create -f raw ics-testing.img 32G
Once the image is created, we can use it as a raw disk image and install an OS. In this case I will install ubuntu 12.04 (AMD64) from an iso image.
The syntax would be
qemu-system-ARCH -vnc none,ipv4 -hda IMAGE_NAME -cdrom /PATH/TO/ISO/FILE -m MEMORY -enable-kvm
for example, if my system arch is
x86-64 and my iso location is
/home/devils/iso/ubuntu-12.04-desktop-amd64.iso with memory as
4G. Also I want to enable kernel based virtualisation.
qemu-system-x86_64 -vnc none,ipv4 -hda ics-testing.img \ -cdrom /home/devils/iso/ubuntu-12.04-desktop-amd64.iso \ -m 4096 -enable-kvm
this will pop up a qemu window. Proceed with the installation and reboot the system.
3. Booting an installed image
Once the installation is complete, boot the image by typing,
qemu-system-x86_64 -vnc none,ipv4 -hda ics-testing.img \ -m 4096 -enable-kvm
now configure the system, its package manager and user’s account. Install Openssh-server and enable ssh logins. If everything is configured, start qemu using,
qemu-system-x86_64 -vnc none,ipv4 -hda ics-testing.img \ -m 4096 -enable-kvm \ -redir tcp:2200::22
-redir tcp:2200::22 redirects TCP traffic on the host port
2200 to the guest machine (QEMU) port
22. This will allow us to SSH into the machine later by connecting to
localhost on port
-vnc none will disble the vnc server.
- ssh into qemu
You can ssh into the running qemu system using a command
ssh -p PORT USER@IP-Address or HOSTNAME
for example, if I want to connect to port
localhostwith username as
ssh -p 2200 qemu-user@localhost
localhostis open and is binded with port
22of qemu system, so we will use
-p 2200as one of the parameter.
4. Creating snapshots of an image
Now as the image is configured and working, we can also create a snapshots of that image and work on it keeping an original image intact.
qemu-img create -f qcow2 -b ORIGINAL_IMAGE_NAME SNAPSHOT_IMAGE_NAME
for example if my original image name is
ics-testing.img and my snapshot image name is
qemu-img create -f qcow2 -b ics-testing.img snapshot.img
-f flag will specify image format. In this case it is
qcow2 which is most versatile qemu-image format. Please refer man-pages for more detail.
5. Booting snapshot image
You can use the snapshot image using
qemu-system-x86_64 -vnc none -hda snapshot.img \ -m 4096 -enable-kvm \ -redir tcp:2200::22
a. You can also specify number of CPU cores using
-smp flag. For example, if you want to assign 4 cores of your physical system to qemu, then specific it as
smp stands for Symmetric-multiprocessing.
b. If you run qemu over the snapshot image, it will corrupt the snapshot image.