Ignition config generation

[castrojo]

Description

Core config generation: assemble Butane YAML from wizard state and compile to Ignition JSON.

Acceptance Criteria

• Use github.com/coreos/butane/config as a Go library
• Use Flatcar Butane variant (variant: flatcar, appropriate spec version)
• Generate storage section (disk wipe, filesystem)
• Generate networkd units (DHCP or static config)
• Generate passwd section (user, SSH keys, optional password hash)
• Generate systemd units for sysext downloads and systemd-sysext enablement
• Support mutually exclusive modes: guided local generation OR external Ignition URL passthrough
• Validate generated config before passing to install step
• Unit tests with golden-file comparison in testdata/

Architecture

internal/ignition owns this. It receives a struct from internal/wizard and returns compiled Ignition JSON bytes.

[castrojo]

Implemented in commits 8f7422e..174b76f. All packages built, tested, and verified in QEMU VM.

[castrojo]

Reopening — audit found 5 acceptance criteria unmet. This is the most incomplete closed issue.

Criteria Status

• Use github.com/coreos/butane/config as a Go library — NOT IMPLEMENTED. The code shells out to the butane CLI binary via runner.RunWithInput(ctx, butaneYAML, "butane", "--strict"). This means butane must be in PATH on the target system.
• Use Flatcar Butane variant (variant: flatcar, spec 1.1.0) — Template correctly generates this
• Generate storage section (disk wipe, filesystem) — NOT IMPLEMENTED. The Butane template has NO disks: section and NO filesystems: section. It only writes /etc/hostname and optional networkd config. The target disk is passed to flatcar-install but never appears in the Ignition config for wipe/format.
• Generate networkd units (DHCP or static config) — Static config generates a proper systemd-networkd unit
• Generate passwd section (user, SSH keys, optional password hash)
• Generate systemd units for sysext downloads and systemd-sysext enablement — NOT IMPLEMENTED. Sysexts only get symlinks in /etc/extensions/ pointing to /opt/extensions/NAME/NAME-VERSION.raw, but there are NO systemd units to actually download those files. The SysextEntry.URL field is never used in the template. (See also open issue bug: Sysext symlinks point to nonexistent files — URL field never used in Ignition output #27)
• Support mutually exclusive modes: guided local generation OR external Ignition URL passthrough — PARTIALLY DONE. install.go handles IgnitionURL, but there is no TUI step to choose between modes. Users cannot enter an external URL through the wizard.
• Validate generated config before passing to install step — NOT IMPLEMENTED. Generated Butane YAML goes directly to butane CLI with no pre-validation.
• Unit tests with golden-file comparison in testdata/

What's missing

This issue has 5 unmet criteria out of 9. The Ignition generation is a skeleton that produces hostname + user + optional static network, but misses critical disk and sysext configuration. The decision to shell out to butane CLI instead of embedding as a Go library was never documented (see also issue #18 spike).