go-kargs: parse and manipulate kernel command line arguments

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Read, set, delete, then write back out kernel command line arguments.

package main

import (
	"fmt"

	kargs "github.com/synackd/go-kargs"
)

func main() {
	// Parse kernel command line arguments
	kargsIn := `nomodeset root=live:https://172.16.0.254/boot-images/compute/base/test console=tty0,115200 console=ttyS0,115200 printk.devkmsg=ratelimit printk.time=1`
	k := kargs.NewKargs([]byte(kargsIn))
	fmt.Println(k)

	// Get all values for an argument
	valConsole, isSetConsole := k.GetKarg("console")
	if isSetConsole {
		fmt.Printf("console: %v\n", valConsole)
	} else {
		fmt.Println("console not set")
	}

	// Works even with a single value
	valRoot, isSetRoot := k.GetKarg("root")
	if isSetRoot {
		fmt.Printf("root: %v\n", valRoot)
	} else {
		fmt.Println("root not set")
	}

	// Get all arguments for a module
	fmt.Println("args for printk " + k.FlagsForModule("printk"))

	// Override multiple args
	if err := k.SetKarg("console", "ttyS1,155200n8"); err != nil {
		fmt.Println("params with new console settings: " + k.String())
	}
}

Output:

nomodeset root=live:https://172.16.0.254/boot-images/compute/base/test console=tty0,115200 console=ttyS0,115200 printk.devkmsg=ratelimit printk.time=1
console: [tty0,115200 ttyS0,115200]
root: [live:https://172.16.0.254/boot-images/compute/base/test]
args for printk devkmsg=ratelimit time=1

Installation

go get github.com/synackd/go-kargs

Import as kargs "github.com/synackd/go-kargs"

Development

This library targets Go 1.23.10 and later. A Makefile provides the local checks that mirror the CI workflows (run make help for the full list):

make test        # run unit tests
make race        # run unit tests with the race detector
make coverage    # run tests and print a coverage summary
make vet         # run go vet
make lint        # run golangci-lint
make govulncheck # run govulncheck
make reuse       # check REUSE compliance
make check       # run all of the above

The REUSE check requires the reuse tool (CI uses version 6.2.0). Install it with pipx install reuse==6.2.0 before running make reuse or make check.

Fuzzing

Native Go fuzz tests cover arbitrary parsing inputs, setting keys and values, and append/set/delete sequences checked against an independent ordered model. make test runs all seed cases and saved regression inputs. Active fuzzing is separate from make check:

make fuzz                           # run each target for 30 seconds, sequentially
make fuzz FUZZTIME=5m               # spend five minutes on each target
make fuzz-parse                     # fuzz the parser only
make fuzz-set                       # fuzz SetKarg only
make fuzz-mutations FUZZPARALLEL=4  # fuzz edit sequences with four workers

The default is two workers. CI fuzzes all three targets for 30 seconds each on pushes to main and pull requests, using the Go version in go.mod.

Go saves minimized failures under testdata/fuzz/<target>/<hash>. Replay a failure with the command Go prints, for example:

go test -run='FuzzParse/<hash>' .

See the Go fuzzing guide for more information.

Documentation

See https://pkg.go.dev/github.com/synackd/go-kargs