VyOS cloud-init

Cloud and virtualized instances of VyOS are initialized using the industry-standard cloud-init. Via cloud-init, the system performs tasks such as injecting SSH keys and configuring the network. In addition, the user can supply a custom configuration at the time of instance launch.

Config Sources

VyOS support three types of config sources.

  • Metadata - Metadata is sourced by the cloud platform or hypervisor. In some clouds, there is implemented as an HTTP endpoint at http://169.254.169.254.
  • Network configuration - This config source informs the system about the network settings like IP addresses, routes, DNS. Available only in several cloud and virtualization platforms.
  • User-data - User-data is specified by the user. This config source offers the ability to insert any CLI configuration commands into the configuration before the first boot.

User-data

Major cloud providers offer a means of providing user-data at the time of instance launch. It can be provided as plain text or as base64-encoded text, depending on cloud provider. Also, it can be compressed using gzip, which makes sense with a long configuration commands list, because of the hard limit to ~16384 bytes for the whole user-data.

The easiest way to configure the system via user-data is the Cloud-config syntax described below.

Cloud-config modules

In VyOS, by default, enabled only two modules:

  • write_files - this module allows to insert any files into the filesystem before the first boot, for example, pre-generated encryption keys, certificates, or even a whole config.boot file.
  • vyos_userdata - the module accepts a list of CLI configuration commands in a vyos_config_commands section, which gives an easy way to configure the system during deployment.

cloud-config file format

A cloud-config document is written in YAML. The file must begin with #cloud-config line. The key used to designate a VyOS configuration is vyos_config_commands. What follows is VyOS configuration using the “set-style” syntax. Both “set” and “delete” commands are supported.

Commands requirements:

  • one command per line
  • if command ends in a value, it must be inside single quotes
  • a single-quote symbol is not allowed inside command or value

The commands list produced by the show configuration commands command on a VyOS router should comply with all the requirements, so it is easy to get a proper commands list by copying it from another router.

The configuration specified in the cloud-config document overwrites default configuration values and values configured via Metadata.

Here is an example cloud-config.

#cloud-config
vyos_config_commands:
  - set system host-name 'vyos-prod-ashburn'
  - set system ntp server 1.pool.ntp.org
  - set system ntp server 2.pool.ntp.org
  - delete interfaces ethernet eth1 address 'dhcp'
  - set interfaces ethernet eth1 address '192.0.2.247/24'
  - set protocols static route 198.51.100.0/24 next-hop '192.0.2.1'

System Defaults/Fallbacks

These are the VyOS defaults and fallbacks.

  • SSH is configured on port 22
  • vyos/vyos credentials if no others specified by data source
  • DHCP on first Ethernet interface if no network configuration is provided

All of these can be overridden using the configuration in user-data.

Troubleshooting

If you encounter problems, verify that the cloud-config document contains valid YAML. Online resources such as https://yamlvalidator.com/ provide a simple tool for validating YAML.

cloud-init logs to /var/log/cloud-init.log. This file can be helpful in determining why the configuration varies from what you expect. You can fetch the most important data filtering output for vyos keyword:

sudo grep vyos /var/log/cloud-init.log