Trivial management of 64 bit virtual machines with qemu
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README.md

qvm

Trivial management of 64 bit virtual machines with qemu.

Warning: THIS REPOSITORY IS DEPRECATED. HAVE A LOOK HERE:

Table of contents

Reasons

See https://blog.franco.net.eu.org/notes/qemu-ssh-tunnel.html

Version

See all qvm releases.

What this script will do

It can handle:

  • Virtual hard disk creation, backup and deletion.
  • Basic network management: three ports are exposed to the host machine (but you can add as many as you want). One of these two ports is SSH.
  • Shared directory between host and guest.
  • Running the virtual machine with a combination of the previous options.

Prerequisites

  • You need a 64 bit machine with virtualization technology and at least 4 GB of RAM.
  • Modify configvmrc based on your needs. Variables are self-explanatory and I have kept mine as an example.

Dependencies

You need to install the following packages and the ones listed for fbopt

Package Executable Version command Package version
GNU Bash /bin/bash $ bash --version GNU bash, version 5.0.3(1)-release
QEMU /bin/qemu-system-x86_64 $ qemu-system-x86_64 --version QEMU emulator version 3.1.0
TigerVNC /bin/vncviewer $ vncviewer --help TigerVNC Viewer 64-bit v1.9.0
OpenSSH /bin/ssh $ ssh -V OpenSSH_7.9p1, OpenSSL 1.1.1a 20 Nov 2018
GNU Coreutils /bin/mkdir, /bin/sleep, /bin/rm $ ${Executable} --version (GNU coreutils) 8.30

Installation

Arch Linux based distros

# pacman -S coreutils openssh tigervnc qemu

Debian based distros

# apt-get install coreutils ssh tigervnc-viewer tigervnc-common qemu qemu-kvm qemu-system-x86

Help

Usage: qvm [OPTION]
Trivial management of 64 bit virtual machines with qemu.

Only a single option is accepted.
By default, the backup vhd is run.
Mandatory arguments to long options are mandatory for short options too.
Options:
    -a, --attach                connect via SSH
    -b, --backup                backup the vhd
    -c, --create                create a new vhd
    -d, --delete                delete the vhd backup
    -h, --help                  print this help
    -i, --install               install the image on a vhd
    -m, --mkdir-shared          create a shared directory
    -n, --nox                   run vm without graphical output
    -o, --orig                  run from the original vhd
    -r, --remote                connect to a remote instance of QVM
    -v, --vnc                   use VNC
    -x, --run                   run the vm

Exit status:
 0  if OK,
 1  if an error occurred.

CC0 License
Written in 2018 by Franco Masotti/frnmst <franco.masotti@live.com>

Setup information and usage

Actions and parameters

You can make some combinations between actions and places. Both of these elements are parameters.

Actions

  • attach
  • backup
  • create
  • delete
  • install
  • mkdir-shared
  • run

Places

  • nox
  • origin
  • remote
  • vnc

Setup

  1. Create a new virtual hard disk and complete the OS installation which can also be done via SSH.

      $ ./qvm --create && ./qvm --install
    
  2. Optionally enable the SSH daemon on the guest machine.

  3. Optionally create a new backup VHD:

      $ ./qvm --backup
    
  4. Now you can run the virtual machine either using the original or the backup virtual hard disk. If you run ./qvm --run the virtual machine will run in graphics mode using the backup hard disk.

  5. Optionally add the following in the guest machine fstab file (/etc/fstab), to enable the shared directory automatically. This avoids entering mount commands by hand.

      host_share  /home/vm/shared  9p  auto,access=any,x-systemd.automount,msize=268435456,trans=virtio,version=9p2000.L  0  0
    

    See also the official documentation Note: to be able to access the shared directory the user and group ids must be the same for the host and guest machines. If needed, change those ids within the guest machine:

    1. connect via VNC
    2. login as root
    3. run: # usermod -u ${new_user_id} "${user_name}" && groupmod -g ${new_group_id} "{group_name}"
    4. run: # chown -R "${user_name}":"{group_name}" /home/"${user_name}"
    5. reboot

Connection to the machine

  • You can also access the virtual machine through SSH:

      $ ./qvm --attach
    

    or, if you are working on another computer,

      $ ./qvm --attach --remote
    

VNC options

The VNC options in this script allow you to connect to a remote instance of QEMU. This is particularly useful if, for example, your local machine does not support virtualization.

Note: the VNC traffic goes through SSH TCP forwarding, so it is encrypted.

Setup

For this to work, you must add the following lines in the SSH daemon configuration of the host computer:

AllowTcpForwarding yes
AllowAgentForwarding yes

Examples

You must run QVM with one of the VNC options on the server side. On the client side you must simply edit the HOST_IP_ADDRESS and HOST_USERNAME variables in the configuration file.

Installation

To intall a virtual machine remotely, on the server side you must run:

$ ./qvm --create && ./qvm --install --vnc

and on the client side:

$ ./qvm --attach --remote --vnc

At this point you should see your virtual machine running in a TigerVNC window. Once the installation is complete you can poweroff the machine and then run:

$ ./qvm --run --vnc

on the server, and

$ ./qvm --attach --remote --vnc

on the client.

Maintenance

You can use the installation method for maintenance as well, for example if the machine is unbootable. Select the appropriate virtual hard disk for the VHD_NAME variable in the configuration file and continue with the installation instructions. You should find the hard disk (usually /dev/sda).

Automatic remote startup

To automatically start the virtual machine from a non-host computer you can use the --remote option. Make sure that both the local (non-host) and the remote host computer have a copy of the QVM repository with the variables correctly set in the configrc file.

This script will start the virtual machine if on the host computer no other virtual machine is running. You can use either a VNC or headless connection. Both of them require that SSH is configured correctly on the computers, i.e. the host must be reachable from the client via SSH. This can be verified by using the --attach --remote options while the virtual machine is already running.

Once you have checked that everyting works, you can add a command alias in your shell configuration file (e.g: ~/.bashrc), something like:

alias vm='/home/user/scripts/qvm/qvm --run --remote --vnc'

because --remote implies --nox by default. If you don't need VNC:

alias vm='/home/user/scripts/qvm/qvm --run --remote'

Interesting applications

Virtual machine hard disk over a network protocol

If you happen to use a form of network filesystem, such as GlusterFS, you can keep the machine hard disk off the host and put it on another computer. There might be a some form of lag depending on the hardware, protocol and network connections.

An example with GlusterFS might be:

VHD_NAME="gluster+tcp://server-address/gluster-volume/"${IMG_NAME}"."${VHD_TYPE}""

This will work provided that you install the QEMU GlusterFS block module package (if it's not already present in the QEMU package itself).

You should consult the QEMU's manual to learn about all possible compatible network filesystems.

Bugs

  • If you want to use --remote and --vnc combined, you must first disable any ControlMaster and ControlPath options associated to the user and host in control of the virtual machine. These options can be found in the client's SSH configuration file which is usually ~/.ssh/config.

License

Creative Commons Zero (CC0).

Trusted source

You can check the authenticity of new releases using my public key.

Instructions, sources and keys can be found at frnmst.gitlab.io/software