Intro
It has been a while since I wanted to blog about nested virtualization, but the good news is I now have a vagrant build to share with you so you can vagrant it up:). KVM started to interest me as soon as I learned that Oracle allowed for hard partitioning on KVM boxes if installed on top of Oracle Linux. I instantly thought of the benefit for customers that were struggling with Oracle licensing under Vmware farms. Anyway, today Oracle Cloud and engineered systems are relying hugely on KVM and the old OVM is slowly being replaced by OLVM manager which orchestrate vm administration on top of KVM hosts.
Nested virtualization
KVM inside VirtualBox
So how to make a Hypervisor (KVM) aware of the Host hardware when it’s itself installed under another Hypervisor layer (virtualbox)? well this is today possible thanks to nested virtualization feature available in the latest version of Virtualbox and it is very simple to enable even after your vm has been provisioned. More on how to enable it in my previous blog.
Please note that itโs actually qemu-kvm thatโs available using nested virtualization here , which is a type 2 hypervisor (virtual hardware emulation).
How to get started
Canโt afford a dedicated host for KVM? I got you covered, you can start exploring KVM right now on your laptop with my vagrant build. Sharing is good, but live labs are even better.
GitHub repo : https://github.com/brokedba/KVM-on-virtualbox
- Clone the repo
C:Usersbrokedba>
git clone https://github.com/brokedba/KVM-on-virtualbox.git C:Usersbrokedba> cd KVM-on-virtualbox
KVM Tools
Virsh
Is a command line interface that can be used to create, destroy, stop start and edit virtual machines and configure the virtual environment (such as virtual networks etc). >> see Cheatsheet
Virt-install
Although this tool is a reference in terms of vm creation, it has never succeeded to create qemu vms on my vm. Which is why I wonโt talk about a it today.
KCLI
This is a wonderful CLI tool thatโs created by karmab and interacts with libvirt API to manage KVM environments from configuring to managing the guest vms. It even interacts with other virtualization providers (KubeVirt, oVirt, OpenStack, VMware vSphere, GCP and AWS) and easily deploy and customize VMs from cloud images. See details in the official Github repository.
I will do some examples using KCLI in this post since It is already shipped with my nested vagrant build.
Virt-manager /Ovirt/OLVM
All these 3 are a set of GUI based management tools to manage VM Guests.
Virt-viewer
Is a Utility to display graphical console for a virtual machine
Examples
Virsh : Create and build a default storage pool (already done in my nested vagrant vm) and describe the host
# mkdir /u01/guest_images # virsh pool-define-as default dir - - - - "/u01/guest_images" # virsh pool-build default
# virsh pool-list --all Name State Autostart ------------ --------- ------------- default active yes [root@localhost ~]# virsh pool-info default Name: default UUID: 2b273ed0-e666-4c52-a383-c47a03727fc1 State: running Persistent: yes Autostart: yes Capacity: 49.97 GiB Allocation: 32.21 MiB Available: 49.94 GiB
[root@localhost ~]# virsh nodeinfo ---> the host is actually my virtualbox vm CPU model: x86_64 CPU(s): 2 CPU frequency: 2592 MHz CPU socket(s): 1 Core(s) per socket: 2 Thread(s) per core: 1 NUMA cell(s): 1 Memory size: 3761104 KiB ---- vm # virsh list --all (list all guest vms including shutdown vms) # virsh dominfo db2 (describe a โdb2โ vm) # virsh edit db2 (edit โdb2โ vm attributes)
--- Reboot Shutdown start VMs # virsh start my-vm # virsh reboot my-vm # virsh shutdown my-vm
CREATE A VM INSIDE A NESTED VIRTUAL MACHINE
-
I will be using KCLI in my example where I will
-
Create a default storage pool and configure it (already done in my vagrant vm)
# kcli create pool -p /u01/guest_images default # kcli list pool +--------------+-------------------------+ | Pool | Path | +--------------+-------------------------+ | default | /u01/guest_images | +--------------+-------------------------+
Since kcli uses docker we will need to update the kcli alias according to the pool path
# alias kcli='docker run --net host -it --rm --security-opt label=disable -v /root/.kcli:/root/.kcli -v /root/.ssh:/root/.ssh -v /u01/guest_images:/u01/guest_images -v /var/run/libvirt:/var/run/libvirt -v $PWD:/workdir quay.io/karmab/kcli'
-
Create a default network (already done in my vagrant vm)
# kcli create network -c 192.168.122.0/24 default # kcli list network +---------+--------+------------------+------+---------+------+ | Network | Type | Cidr | Dhcp | Domain | Mode | +---------+--------+------------------+------+---------+------+ | default | routed | 192.168.122.0/24 | True | default | nat | +---------+--------+------------------+------+---------+------+
KCLI makes it very easy to download an image from the cloud repository as shown in below example
-
Download ubuntu 1803 from ubuntu cloud image repository
# kcli download image ubuntu1804 -p default Using url https://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img... # kcli list image +----------------------------------------------------+ | Images | +----------------------------------------------------+ | /u01/guest_images/bionic-server-cloudimg-amd64.img | +----------------------------------------------------+
- You can also use Curl if you have a specific image you want to download
# curl โsL image-URL โo /Pool/Path/image.img
-
Create a vm
Once the image is in the storage pool you only have to run the kcli create command as below ( see syntax)
# kcli create vm ubuntuvm -i ubuntu1804 -P network=default -P virttype=qemu โP memory=512 -P numcpus=1 Deploying vm ubuntu_vm from profile ubuntu1804... ubuntu_vm created on local
# kcli list vm +----------+-------+--------------------------------------+-----+------------+ | Name | Status| Ips | Source |Plan | Profile | +----------+-------+--------------+-----------------------+-----+------------+ | ubuntuvm | up | 192.168.122.5| bionic-server*md64.img|kvirt| ubuntu1804 | +----------+-------+--------------+-----------------------+-----+------------+ Syntax: usage : kcli create vm [-h] [-p PROFILE] [--console] [-c COUNT] [-i IMAGE] [--profilefile PROFILEFILE] [-P PARAM] [--paramfile PARAMFILE] [-s] [-w] [VMNAME]
Login to the vm
- The IP address will take some time before itโs assigned but when itโs done, just log in using ssh. kcli creates the vm based on the default ssh key (~/id_rsa).
# kcli ssh ubuntuvm Welcome to Ubuntu 18.04.6 LTS (GNU/Linux 4.15.0-163-generic x86_64) ubuntu@ubuntuvm:~$ uname -a Linux ubuntuvm 4.15.0-163-generic #171-Ubuntu SMP Fri Nov 5 11:55:11 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
# kcli create vm ubuntuvm -i ubuntu1804 -P network=default -P virttype=qemu -P cmds=['echo root:unix1234 | chpasswd']
# virsh console ubuntuvm Connected to domain ubuntuvm ubuntuvm login: root Password:
Welcome to Ubuntu 18.04.6 LTS (GNU/Linux 4.15.0-163-generic x86_64) root@ubuntuvm:~#
-
Download an Image
KCLI tips
-
kcli configuration is done in ~/.kcli directory, that you need to manually create (done in my vagrant build already). It will contain:
- config.yml generic configuration where you declare clients.
- profiles.yml stores your profiles where you combine things like memory, numcpus and all supported parameters into named profiles to create vms from
For example, you could create the same vm described earlier by storing the vm specs in the profiles.yml
--- excerpt from ~/.kcli/profiles.yml local_ubuntu1804: image: bionic-server-cloudimg-amd64.img numcpus: 1 memory: 512 nets: - default pool: default cmds: - echo root:unix1234 | chpasswd
Then call the named profile using the โi argument during the creation of the vm
# kcli create vm ubuntuvm โi local_ubuntu1804
Conclusion
KVM from VirtualBox.