After some iterations in our internal tools, we realised that the installation process was too slow and we always repeated the same steps. Of course, any good sysadmin will scream "AUTOMATION!" and so did we. Therefore, we started looking for different ways to improve our deployments.
We had a look at existing frameworks that manage Bhyve, but none of them had a feature that we find really important: having a centralized repository of VM images. For instance, SmartOS applies this method successfully by having a backend server that stores a catalog of VMs and Zones, meaning that new instances can be deployed in a minute at most. This is a game changer if you are really busy in your day-to-day operations.
Since we are not great programmers, we decided to leverage the existing tools to achieve the same results. This is, having a centralised repository of Bhyve images in our data centers. The following building blocks are used:
- The ZFS snapshot of an existing VM. This will be our VM template.
- A modified version of oneoff-pkg-create to package the ZFS snapshots.
- pkg-ssh and pkg-repo to host a local FreeBSD repo in a FreeBSD jail.
- libvirt to manage our Bhyve VMs.
- The ansible modules virt, virt_net and virt_pool.
- We write a yml dictionary to define the parameters needed to create a new VM:
- VM template (name of the pkg that will be installed in /bhyve/images)
- VM name, cpu, memory, domain template, serial console, etc.
- This dictionary will be kept in the corresponding host_vars definition that configures our Bhyve host server.
- The Ansible playbook:
- installs the package named after the VM template (ZFS snapshot).e.g. pkg install FreeBSD-10.3-RELEASE-ZFS-20G-20170515.
- uses cat and zfs receive to load the ZFS snapshot in a new volume.
- calls the libvirt modules to automatically configure and boot the VM.
- The Sysadmin logs in the new VM and adjusts the hostname and network settings.
- Run a separate Ansible playbook to configure the new VM as usual.
Once automated, the installation process needs 2 minutes at most, compared with the 30 minutes needed to manually install VM plus allowing us to deploy many guests in parallel.
- Sample config for FreeBSD https://people.freebsd.org/~rodrigc/libvirt-bhyve/libvirt-bhyve.html
- bhyve driver for libvirt http://libvirt.org/drvbhyve.html
- virsh examples https://wiki.libvirt.org/page/VM_lifecycle#Creating_a_domain
- migrating VMs w/o shared storage https://hgj.hu/live-migrating-a-virtual-machine-with-libvirt-without-a-shared-storage/
- xml reference http://libvirt.org/formatdomain.html
- Virtual networking https://wiki.libvirt.org/page/VirtualNetworking