rhdp-instance-config

name: rhdp-instance-config description: >- Guard rails for editing config/instances.yaml and related RHDP/agnosticD lab VM definitions. Use when modifying instances.yaml, userdata blocks, AnsibleGroup tags, ui-config.yml tabs, or setup-automation scripts. Prevents known boot-hang and deployment pitfalls.

RHDP Instance Configuration Guide

This lab runs on the Red Hat Demo Platform (RHDP) via the agnosticD deployer. The deployer reads config/instances.yaml to provision VMs and applies automation based on each VM's AnsibleGroup tag. Several non-obvious interactions between these settings have caused multi-hour debugging sessions.

Critical Rules

1. AnsibleGroup Must Be "isolated" for All VMs

tags:
  - key: AnsibleGroup
    value: isolated    # CORRECT — agnosticD leaves this VM alone

Never use bastions unless the VM genuinely needs agnosticD-managed SSH key distribution and password setup. When a VM is tagged bastions:

• The deployer SSHs into it during provisioning to push keys and reset passwords.
• If credentials don't match what the deployer expects, it hangs/retries for minutes, causing massive boot delays (~20 min+).
• The deployer only supports one bastion host. Tagging multiple VMs as bastions will cause failures.

Our lab handles its own SSH and password setup via cloud-init userdata, so every VM should be isolated.

2. Userdata Scalar Must Be |- (Literal Block), Never >- (Folded)

# CORRECT — preserves newlines, cloud-init can parse each directive
userdata: |-
  #cloud-config
  user: rhel
  password: ansible123!
  chpasswd: { expire: False }
  runcmd:
    - echo "PasswordAuthentication yes" > /etc/ssh/sshd_config.d/50-cloud-init.conf
    - systemctl reload sshd

# WRONG — folds all lines into one, cloud-init receives garbage
userdata: >-
  #cloud-config
  user: rhel
  ...

In YAML:

• |- = literal block scalar, preserves newlines (what cloud-init needs)
• >- = folding scalar, joins lines with spaces (breaks cloud-init entirely)

When >- is used, passwords never get set, SSH password auth is never enabled, and any automation that tries to SSH with a password will fail silently.

3. Every VM Needs Its Own Userdata Block

Don't assume the deployer handles password/SSH setup — it won't for isolated nodes. Each VM definition in instances.yaml must include the full userdata block with cloud-config for user, password, chpasswd, and the sshd runcmd.

4. UI Config Terminal Routing

In ui-config.yml, terminal tabs use two different keys:

• type: accepts only predefined values like terminal (chart default route)
• url: accepts explicit paths like /wetty_control

Never put a path in type: — it causes "Port and url not defined" errors.

# CORRECT — explicit WeTTY path goes in url:
- name: AAP terminal
  url: /wetty_control

# WRONG — type: only accepts predefined values, not paths
- name: AAP terminal
  type: /wetty_control

# RISKY — "terminal" resolves to whatever the chart default is (often containerlab)
- name: AAP terminal
  type: terminal

Use explicit url: /wetty_<vmname> for every terminal tab. Only use type: terminal if you're certain the chart default route points where you want.

5. VSCode Service Naming

The vscode VM service and route names must be consistent simple names (not suffixed with port numbers):

services:
  - name: vscode          # not "vscode-8080"
routes:
  - name: vscode          # must match the service name
    service: vscode

Checklist When Editing instances.yaml

• All VMs have value: isolated (not bastions)
• All userdata: fields use |- scalar (not >-)
• Every VM has a complete userdata cloud-config block
• Service names and route names are consistent
• networks: block is present on each VM that needs network access
• VSCode image is rhel-9.6 (not devtools-ansible — code-server is installed by setup-vscode.sh at runtime)

Architecture Quick Reference

Setup scripts in setup-automation/ run as cloud-init runcmd or are triggered by the deployer for the respective VM. They handle everything (package install, code-server setup, EE pulls, repo cloning) because all VMs are isolated.