Virtual machine made easy

In this post, I’ll present how I deal with my virtual machines on a server an access them remotely.

Setup - server side

In the post about the network configuration, a virtual bridge named br0 has been configured, especially for the virtual machines. A virtual machine connected to this brige will have a connection to the network equivalent to the server connection, and will be seen by the network as another machine on the same interface(s) as the server.

Install the required packages:

cli@server:~$ sudo apt-get install libvirt-bin

Make sure your user is in the libvirt group:

sudo usermod -aG libvirt cli
sudo usermod -aG libvirt local

ubuntu 16.04 and 18.04 kernels have nesting (running vm inside vm) enabled by default, for other distributions, nesting can be enable like this test:

# If you have an Intel CPU, use this:
$ cat /etc/modprobe.d/kvm_intel.conf
options kvm-intel nested=Y
# If you have an AMD CPU, then this:
$ cat /etc/modprobe.d/kvm_amd.conf
options kvm-amd nested=1

Virtual disks

A pool for storing virtual machines already exists in /var/lib/libvirt/images

Setup a pool for boot disks

virsh pool-define-as boot --type dir --target /var/lib/libvirt/boot
virsh pool-autostart boot
virsh pool-start boot

Get some linux distributions to play with:

An iso installer image for xubuntu 18.04

A ready to run image of openwrt (release lede-17.01)

sudo -i
cd /var/lib/libvirt/boot
wget http://ftp.uni-kl.de/pub/linux/ubuntu-dvd/xubuntu/releases/18.04/release/xubuntu-18.04-desktop-amd64.iso
chown libvirt-qemu:kvm xubuntu-18.04-desktop-amd64.iso
cd ../images
https://downloads.openwrt.org/releases/17.01.4/targets/x86/64/lede-17.01.4-x86-64-combined-squashfs.img
chown libvirt-qemu:kvm lede-17.01.4-x86-64-combined-squashfs.img
exit

Since we have create a bridge for the virtual machines, we can safely disable the default network created by libvirt:
```
virsh net-autostart default --disable
virsh net-destroy default
virsh net-undefine default
```

Disable snapshots for virtual disks

Snaphshotting multi-gigabyte virtual disk image is not a good idea, it ended up filling my disks very fast, and since I don’t have enough space on the SSD for the virtual machines, let’s move them to the HDDs.

Stop libvirt
```
   sudo systemctl stop libvirt-bin
```

Create the subvolume and move data (if libvirt is already installed)

   sudo -i
   mkdir -p /tmp/work/root /tmp/work/data
   mount /dev/mapper/root-root /tmp/work/root
   mount /dev/mapper/data-data /tmp/work/data
   cd /tmp/work
   btrfs subvolume create data/@var-lib-libvirt
   mv root/@/var/lib/libvirt/* data/@var-lib-libvirt/
   exit

Add the required line to /etc/fstab:

/dev/mapper/data-data /var/lib/libvirt btrfs noatime,subvol=@var-lib-libvirt 0 2

Mount and restart libvirt

sudo mount -a
sudo systemctl start libvirt-bin

Setup - client side

Install the required packages:

cli@workstation:~$ sudo apt-get install virt-manager

copy your ssh public key to the server

cli@workstation:~$ ssh-copy-id cli@server

Start virt-manager, File > new connection…
- Hypervisor : qemu/kvm
- Connect to remote host : checked
- username : cli
- hostname : server
- Connect

Testing - client side - test the xubuntu image

Select the server connection
File > new virtual machine (or the new virtual machine button).
Step 1
- Verify the connection selected is server one
- Select Local media
- Forward
Step 2
- Select use ISO image and browse…, select boot/xubuntu-18.04-desktop-amd64.iso then Choose volume
- OS type : Linux
- Version : Ubuntu 16.04 - Forward
Step 3
- 1024 MB RAM and 1 CPU should be sufficient for testing - Forward
Step 4
- 15 Go should be sufficient for testing - Forward
Step 5
- Choose a name
- Network selection : specify a shared device name:
  - br0 ⚠ It seems there is a bug in 18.04, since the br0 is listed when the server is running 16.04
- Forward
Now you can play with that new image

~~~

Question, remark, bug? Don't hesitate to contact me or report a bug.