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 only supported top-level keys are vyos_config_commands and write_files. The use of these keys is described in the following two sections.

Initial Configuration

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 that appends configuration at the time of first boot.

#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.

Command Execution at Initial Boot

VyOS supports the execution of operational commands and linux commands at initial boot. This is accomplished using write_files to certain files in the /opt/vyatta/etc/config/scripts directory. Commands specified in opt/vyatta/etc/config/scripts/vyos-preconfig-bootup.script are executed prior to configuration. The /opt/vyatta/etc/config/scripts/vyos-postconfig-bootup.script file contains commands to be executed after configuration. In both cases, commands are executed as the root user.

Note that the /opt/vyatta/etc/config is used instead of the /config/scripts directory referenced in the Command Scripting section of the documentation because the /config/script directory isn’t mounted when the write_files module executes.

The following example shows how to execute commands after the initial configuration.

#cloud-config
write_files:
  - path: /opt/vyatta/etc/config/scripts/vyos-postconfig-bootup.script
    owner: root:vyattacfg
    permissions: '0775'
    content: |
      #!/bin/vbash
      source /opt/vyatta/etc/functions/script-template
      filename=/tmp/bgp_status_`date +"%Y_%m_%d_%I_%M_%p"`.log
      run show ip bgp summary >> $filename

If you need to gather information from linux commands to configure VyOS, you can execute commands and then configure VyOS in the same script.

The following example sets the hostname based on the instance identifier obtained from the EC2 metadata service.

#cloud-config
write_files:
  - path: /opt/vyatta/etc/config/scripts/vyos-postconfig-bootup.script
    owner: root:vyattacfg
    permissions: '0775'
    content: |
      #!/bin/vbash
      source /opt/vyatta/etc/functions/script-template
      hostname=`curl -s http://169.254.169.254/latest/meta-data/instance-id`
      configure
      set system host-name $hostname
      commit
      exit

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