Using QEMU

I use QEMU to test my ansible-desktop repository (automatic setup of a Debian workstation using Ansible). This page acts as a personal reminder about managing the QEMU image.

1. [host] Install the qemu-system-x86 package. This should install qemu-utils as a recommended package, which provides qemu-img.

2. [host] Create an image:

   qemu-img create debian.img 8G
   

3. [host] Boot the image using QEMU. Pass it the Debian iso as an argument:

   qemu-system-x86_64 -hda debian.img -cdrom ~/tmp/downloads/debian-11.0.0-amd64-netinst.iso -boot d -m 2048 -enable-kvm
   

4. [guest] Install Debian.

5. [host] Run the image with a port forwarding from the host's port 2222 to the guest's port 22:

   qemu-system-x86_64 -hda debian.img -m 2048 -enable-kvm -net user,hostfwd=tcp::2222-:22 -net nic
   

6. [guest] As root, install openssh-server.

7. [host] You should be able to connect to the guest from the host using SSH:

   ssh alc@localhost -p 2222
   

8. [host] If necessary, transfer some useful files from the host to the guest…

   scp -P 2222 file.txt alc@localhost:/home/alc
   

   [guest] …or from guest to host (using the local network):

   scp file.txt alc@[ip-on-local-network]:/home/alc
   

9. [host] Run the image in snapshot mode so you won't alter it:

   qemu-system-x86_64 -hda debian.img -m 2048 -snapshot -enable-kvm
   

At this point I can test things out and always return to the same basic machine state.