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fix(cloudinit): merge cloud-config documents before the seed is written #97

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Merged
NovusEdge merged 1 commit into from
Sep 6, 2026
Merged

fix(cloudinit): merge cloud-config documents before the seed is written #97

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80 changes: 7 additions & 73 deletions internal/cloudinit/cloudinit.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@ import (

"github.com/novusedge/stoat/internal/config"
"github.com/novusedge/stoat/internal/guest"
"gopkg.in/yaml.v3"
)

// User is the account the seed creates. Anything provisioned through this
Expand Down Expand Up @@ -93,13 +92,12 @@ func extraPackages(osName string) string {
return b.String()
}

// userData builds the seed's user-data as a cloud-config-archive: the
// hardware-proven users: block (parameterized by the guest's shell), the
// OS's own extra packages if it needs any, and every selected cloud
// recipe's body verbatim, each as its own document. cloud-init merges the
// documents itself; see buildArchive. This package does not parse any
// document for packages:/runcmd:, so a fragment using write_files: or any
// other key survives instead of being silently dropped.
// userData builds the seed's user-data: the hardware-proven users: block
// (parameterized by the guest's shell), the OS's own extra packages if it
// needs any, and every selected cloud recipe's body. mergeDocs folds them
// into one #cloud-config document. Nothing here looks for packages: or
// runcmd: by name, so a fragment using write_files: or any other key
// survives.
func userData(v *config.VM, pubkey string, recipeBodies []string) (string, error) {
base := fmt.Sprintf(userDataTemplate, guestShell(v.OS), pubkey, consolePasswordBlock(v.ConsolePassword))

Expand All @@ -112,7 +110,7 @@ func userData(v *config.VM, pubkey string, recipeBodies []string) (string, error
}
docs = append(docs, recipeBodies...)

return buildArchive(docs)
return mergeDocs(docs)
}

// SkipShares reports whether osName's guest.toml sets backend.cloudinit's
Expand Down Expand Up @@ -227,70 +225,6 @@ func ValidateFragment(body string) (annotated string, err error) {
return string(out), nil
}

// mergeHow is the explicit merge directive every document in the archive
// carries. cloud-init's default merge is dict(no_replace)+list()+str(): two
// documents both declaring packages: do NOT append, the first one wins and
// the second is silently discarded. append+recurse_list makes list values
// (packages:, runcmd:, ...) concatenate instead.
const mergeHow = "list(append)+dict(recurse_list)"

// withMergeHow injects merge_how as a top-level key into a #cloud-config
// document body.
//
// A document's own merge_how does not govern how it merges in. It governs
// how the NEXT document in the archive merges into the accumulated result
// (cloud-init's merging.rst, "Specifying multiple types"). The first
// document always merges with the built-in default, regardless of what it
// declares.
//
// Every document except the last needs the directive, or a later document
// silently loses to an earlier one. Callers may pass any number of recipe
// bodies, so the last one is not known in advance; every document gets the
// directive. This matches cloud-init's own worked example in merging.rst,
// which puts merge_how in both halves of a two-document merge.
func withMergeHow(doc string) string {
directive := fmt.Sprintf("merge_how: %q\n", mergeHow)
if rest, ok := strings.CutPrefix(doc, "#cloud-config\n"); ok {
return "#cloud-config\n" + directive + rest
}
return directive + doc
}

// archiveDoc is one entry of a cloud-config-archive: cloud-init's own
// format for a list of {type, content} documents that it merges itself,
// replacing the packages:/runcmd:-only splicing this package used to do by
// hand (see doc/examples/cloud-config-archive.txt upstream).
type archiveDoc struct {
Type string `yaml:"type"`
Content string `yaml:"content"`
}

// buildArchive renders docs as a cloud-config-archive. The
// "#cloud-config-archive" header is required verbatim on its own first
// line: it is what NoCloud's format-detection matches on to unpack the
// payload as an archive rather than parse it (and fail) as one big
// #cloud-config document. Each doc is carried through withMergeHow so the
// archive as a whole merges by appending rather than by cloud-init's
// default first-one-wins.
func buildArchive(docs []string) (string, error) {
// An archive is a top-level YAML list. cloud-init 24.4 on AlmaLinux 9 and
// Rocky 9 calls .get() on the parsed user-data before it checks the type,
// so the list fails the init-local stage and pins `cloud-init status` at
// error for the life of the VM. One document does not need the wrapper.
if len(docs) == 1 {
return withMergeHow(docs[0]), nil
}
items := make([]archiveDoc, len(docs))
for i, d := range docs {
items[i] = archiveDoc{Type: "text/cloud-config", Content: withMergeHow(d)}
}
out, err := yaml.Marshal(items)
if err != nil {
return "", fmt.Errorf("marshaling cloud-config-archive: %w", err)
}
return "#cloud-config-archive\n" + string(out), nil
}

// Seed writes <v.OvlDir()>/seed/{user-data,meta-data} and builds
// <v.OvlDir()>/seed.iso (ISO9660, volume label CIDATA) via xorriso. It
// returns the iso path. recipeBodies are the bodies of v's selected cloud
Expand Down
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