#tinycorelinux

Today we're announcing the official release of cloud-init deployed on our On-Prem virtual appliances.

The entire setup is fully Open Source under the permissive MIT license, and can be used/tweaked by anyone as they see fit.

Cloud-init on-premises

For those unfamiliar with cloud-init, it's a tool installed on the appliance which allows it to be configured with certain settings on boot. The settings are not pre-baked into the VM, but rather fetched from the VM's host (ex: EC2, VMware, Proxmox, MaaS, etc). They can be obtained in the form of a removable drive (ex: /dev/sr0), or from a "Metadata URL" such as http://169.254.169.254/.

Pre-configured settings are fine for defaults, but there has always been a need to provide additional settings such as NTP, network, DNS, storage, apitoken, before the VM is first booted. That's where cloud-init comes in. It allows a true zero-touch deployment of On-Prem appliances on various on-prem AND cloud providers.

Unfortunately with TinyCore Linux and an immutable OS, that "feature" has always been impossible to implement, until now.

The changes we've implemented for cloud-init to work on our appliances only add a few MB (~3.8MiB) to the size of the appliance, and require an ugrade from Python v2.7 to Python v3.

How it works

We add a system overlay into the TinyCore Linux rootfs, along with 3 new extensions (and their dependencies) which are loaded on boot:

ifupdown.tcz

cloud-init.tcz

cloud-init-deps.tcz

The /opt/bootsync.sh will run cloud-init and then try to setup networking through /opt/network.sh, which is simply calling cloud-init once more with different arguments. The reason for this is to provide backward compatibility for existing On-Prem TinyCore deployments.

Note: If there is no usage of the network.tcz, jidoteki-admin.tcz, or jidoteki-admin-api.tcz extensions, /opt/network.sh can be removed from /opt/bootsync.sh and replaced with:

/usr/local/bin/cloud-init modules --mode config

Each step in the cloud-init runs can be found in /etc/cloud/cloud.cfg.

The config modules are bootcmd which are the actual Shell scripts found in /etc/cloud/scripts.

Customizations can and should be added to custom.sh and custom-once.sh. If it's not immediately obvious, the once.sh and custom-once.sh scripts will only run once per boot. Unlike typical cloud-init installations, the once scripts will run again on reboot (because the OS is immutable).

Userdata, Metadata, Vendordata

The Shell scripts provided for this cloud-init deployment will read settings from various files on the system, including any userdata or vendordata provided to the system.

The order of precendence for reading configuration values are:

backed up files from /opt/.filetool.lst

userdata from /var/lib/cloud/instance/user-data.txt

vendordata from /var/lib/cloud/seed/nocloud-net/vendor-data

Note: Metadata is only currently used by cloud-init to configure SSH public-keys. All other metadata is ignored, but still accessible to applications running on the TinyCore Linux appliance.

Userdata

Tested with EC2, Proxmox, and NoCloud, the userdata will be discovered by cloud-init and read directly from /var/lib/cloud/instance/user-data.txt. From testing, it appears cloud-init handles Base64 decoding of userdata automatically provided by EC2.

Note: Userdata is not parsed by cloud-init, but rather read manually by various Shell scripts. This means it is not possible for userdata to overwrite values from /etc/cloud/cloud.cfg, and it is not possible to provide userdata which contains a shell script or other malicious features. Userdata should only contain key: value pairs.

Vendordata

The vendor-data is added to the /var/lib/cloud/seed/nocloud-net/ directory on the rootfs. It is also possible to add a network-config (v1 config) to that directory for pre-configuring the network.

Note: Similar to userdata, the vendor-data is not parsed by cloud-init and should only contain key: value pairs (except for network-config, which is parsed by cloud-init's net-convert tool).

More info

For more information, please see the README.md from our Open Soure repository.

Moving forward

We're hoping to add cloud-init to all our customer appliances in the coming month, so all their customers can benefit from the advantages cloud-init provides.