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Add partial config file functionality to cEOS #3103

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43f179d
Add partial config file functionality
CapnCheapo Mar 10, 2026
8ba5abd
Updated ceos docs to include partial config details
CapnCheapo Apr 7, 2026
d52954c
Merged upstream changes
CapnCheapo Apr 7, 2026
2a83aa7
Merge upstream changes
CapnCheapo Apr 7, 2026
5bcf9b7
Merge upstream changes
CapnCheapo Apr 7, 2026
bdffc96
Enhance documentation on user-defined cEOS configs
CapnCheapo Apr 7, 2026
c95f445
Partial config test cases
CapnCheapo Apr 7, 2026
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1 change: 1 addition & 0 deletions nodes/ceos/ceos.cfg
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Original file line number Diff line number Diff line change
Expand Up @@ -34,5 +34,6 @@ management api http-commands
vrf {{ .Env.CLAB_MGMT_VRF }}
no shutdown
{{end}}
{{ .PartialCfg }}

@ankudinov ankudinov Apr 30, 2026

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AI remark, not tested in the lab:
Full configs still get Go template rendering, but no longer pass through SubstituteEnvsAndTemplate, so ${VAR} expansion regresses. Partial configs are inserted as .PartialCfg, so a partial file containing {{ .ShortName }} would be emitted literally instead of rendered.

Please add a test case for env expansion.

!
end
61 changes: 57 additions & 4 deletions nodes/ceos/ceos.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
package ceos

import (
"bytes"
"context"
_ "embed"
"encoding/json"
Expand All @@ -16,6 +17,7 @@ import (
"path/filepath"
"regexp"
"strings"
"text/template"

"github.com/charmbracelet/log"
clabconstants "github.com/srl-labs/containerlab/constants"
Expand Down Expand Up @@ -61,8 +63,7 @@ var (
)

// Register registers the node in the NodeRegistry.
func Register(r *clabnodes.NodeRegistry) {
generateNodeAttributes := clabnodes.NewGenerateNodeAttributes(generateable, generateIfFormat)
func Register(r *clabnodes.NodeRegistry) { generateNodeAttributes := clabnodes.NewGenerateNodeAttributes(generateable, generateIfFormat)
platformAttrs := &clabnodes.PlatformAttrs{
ScrapliPlatformName: scrapliPlatformName,
NapalmPlatformName: NapalmPlatformName,
Expand All @@ -81,6 +82,21 @@ func Register(r *clabnodes.NodeRegistry) {

type ceos struct {
clabnodes.DefaultNode
bootCfg string
partialStartupCfg string
}

type CeosTemplateData struct {
ShortName string
Env map[string]string
MgmtIntf string
MgmtIPv4Address string
MgmtIPv4PrefixLength int
MgmtIPv4Gateway string
MgmtIPv6Address string
MgmtIPv6PrefixLength int
MgmtIPv6Gateway string
PartialCfg string
}

// intfMap represents interface mapping config file.
Expand Down Expand Up @@ -209,16 +225,24 @@ func (n *ceos) createCEOSFiles(ctx context.Context) error {
return err
}

// default to embedded boilerplate config
n.bootCfg = cfgTemplate

// use startup config file provided by a user
if nodeCfg.StartupConfig != "" {
c, err := os.ReadFile(nodeCfg.StartupConfig)
if err != nil {
return err
}
cfgTemplate = string(c)

if clabutils.IsPartialConfigFile(nodeCfg.StartupConfig) {
n.partialStartupCfg = string(c)
} else {
n.bootCfg = string(c)
}
}

err = n.GenerateConfig(nodeCfg.ResStartupConfig, cfgTemplate)
err = n.genBootConfig()
if err != nil {
return err
}
Expand Down Expand Up @@ -272,6 +296,35 @@ func (n *ceos) createCEOSFiles(ctx context.Context) error {
return err
}

func (n *ceos) genBootConfig() error {
nodeCfg := n.Config()

tplData := CeosTemplateData{
ShortName: n.Cfg.ShortName,
Env: nodeCfg.Env,
MgmtIntf: nodeCfg.MgmtIntf,
MgmtIPv4Address: nodeCfg.MgmtIPv4Address,
MgmtIPv4PrefixLength: nodeCfg.MgmtIPv4PrefixLength,
MgmtIPv4Gateway: nodeCfg.MgmtIPv4Gateway,
MgmtIPv6Address: nodeCfg.MgmtIPv6Address,
MgmtIPv6PrefixLength: nodeCfg.MgmtIPv6PrefixLength,
MgmtIPv6Gateway: nodeCfg.MgmtIPv6Gateway,
PartialCfg: n.partialStartupCfg,
}

t, err := template.New("ceos-config").Funcs(clabutils.CreateFuncs()).Parse(n.bootCfg)
if err != nil {
return fmt.Errorf("failed to parse cfg template for node %q: %w", n.Cfg.ShortName, err)
}

buf := new(bytes.Buffer)
if err := t.Execute(buf, tplData); err != nil {
return fmt.Errorf("failed to execute cfg template for node %q: %w", n.Cfg.ShortName, err)
}

return clabutils.CreateFile(nodeCfg.ResStartupConfig, buf.String())
}

// Func that Places the Certificates in the right place and format.
func (n *ceos) createCEOSCertificates() error {
if *n.Cfg.Certificate.Issue {
Expand Down
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