Support cosa run --kargs

For the use case of enabling systemd debugging, etc.
coreos#1263 (comment)

Author: cgwalters

mantle/cmd/kola/qemuexec.go

@@ -39,6 +39,7 @@ var (
 
 	hostname string
 	ignition string
+	kargs    string
 	knetargs string
 
 	forceConfigInjection bool
@@ -47,6 +48,7 @@ var (
 func init() {
 	root.AddCommand(cmdQemuExec)
 	cmdQemuExec.Flags().StringVarP(&knetargs, "knetargs", "", "", "Arguments for Ignition networking on kernel commandline")
+	cmdQemuExec.Flags().StringVarP(&kargs, "kargs", "", "", "Additional kernel arguments applied (ephemerally) to the first boot")
 	cmdQemuExec.Flags().BoolVarP(&usernet, "usernet", "U", false, "Enable usermode networking")
 	cmdQemuExec.Flags().StringVarP(&hostname, "hostname", "", "", "Set hostname via DHCP")
 	cmdQemuExec.Flags().IntVarP(&memory, "memory", "m", 0, "Memory in MB")
@@ -61,6 +63,7 @@ func runQemuExec(cmd *cobra.Command, args []string) error {
 	if len(knetargs) > 0 {
 		builder.IgnitionNetworkKargs = knetargs
 	}
+	builder.EphemeralKernelArguments = kargs
 	defer builder.Close()
 	builder.Firmware = kola.QEMUOptions.Firmware
 	if kola.QEMUOptions.DiskImage != "" {

mantle/platform/qemu.go

@@ -149,6 +149,9 @@ type QemuBuilder struct {
 	Pdeathsig  bool
 	Argv       []string
 
+	// EphemeralKernelArguments are appended to the bootloader config
+	EphemeralKernelArguments string
+
 	// IgnitionNetworkKargs are written to /boot/ignition
 	IgnitionNetworkKargs string
 
@@ -356,9 +359,8 @@ func (gf *coreosGuestfish) destroy() {
 	}
 }
 
-// setupIgnition copies the ignition file inside the disk image and/or sets
-// networking kernel arguments
-func setupIgnition(confPath string, knetargs string, diskImagePath string, diskSectorSize int) error {
+// setupPreboot performs changes necessary before the disk is booted
+func setupPreboot(confPath, knetargs, kargs string, diskImagePath string, diskSectorSize int) error {
 	gf, err := newGuestfish(diskImagePath, diskSectorSize)
 	if err != nil {
 		return err
@@ -383,6 +385,34 @@ func setupIgnition(confPath string, knetargs string, diskImagePath string, diskS
 		}
 	}
 
+	if kargs != "" {
+		confpathout, err := exec.Command("guestfish", gf.remote, "glob-expand", "/loader/entries/ostree*conf").Output()
+		if err != nil {
+			return errors.Wrapf(err, "finding bootloader config path")
+		}
+		confs := strings.Split(strings.TrimSpace(string(confpathout)), "\n")
+		if len(confs) != 1 {
+			return fmt.Errorf("Multiple values for bootloader config: %v", confpathout)
+		}
+		confpath := confs[0]
+
+		origconf, err := exec.Command("guestfish", gf.remote, "read-file", confpath).Output()
+		if err != nil {
+			return errors.Wrapf(err, "reading bootloader config")
+		}
+		var buf strings.Builder
+		for _, line := range strings.Split(string(origconf), "\n") {
+			if strings.HasPrefix(line, "options ") {
+				line += " " + kargs
+			}
+			buf.Write([]byte(line))
+			buf.Write([]byte("\n"))
+		}
+		if err := exec.Command("guestfish", gf.remote, "write", confpath, buf.String()).Run(); err != nil {
+			return errors.Wrapf(err, "writing bootloader config")
+		}
+	}
+
 	if err := exec.Command("guestfish", gf.remote, "umount-all").Run(); err != nil {
 		return errors.Wrapf(err, "guestfish umount failed")
 	}
@@ -443,8 +473,9 @@ func (builder *QemuBuilder) addDiskImpl(disk *Disk, primary bool) error {
 		// If the board doesn't support -fw_cfg or we were explicitly
 		// requested, inject via libguestfs on the primary disk.
 		requiresInjection := builder.Config != "" && (builder.ForceConfigInjection || !builder.supportsFwCfg())
-		if requiresInjection || builder.IgnitionNetworkKargs != "" {
-			if err = setupIgnition(builder.Config, builder.IgnitionNetworkKargs, dstFileName, disk.SectorSize); err != nil {
+		if requiresInjection || builder.IgnitionNetworkKargs != "" || builder.EphemeralKernelArguments != "" {
+			if err = setupPreboot(builder.Config, builder.IgnitionNetworkKargs, builder.EphemeralKernelArguments,
+				dstFileName, disk.SectorSize); err != nil {
 				return errors.Wrapf(err, "ignition injection with guestfs failed")
 			}
 		}

src/cmd-run

@@ -17,6 +17,7 @@ BUILDID=latest
 IMAGE_TYPE=qemu
 HOSTNAME=
 VM_DISK=
+KARGS=
 DISK_CHANNEL=virtio
 VM_MEMORY=2048
 VM_NCPUS="${VM_NCPUS:-${QEMU_PROCS}}"
@@ -36,6 +37,7 @@ Options:
     --size GB             Disk size in GB (matches base by default)
     --user USERNAME       Create user USERNAME via Ignition (if not already extant) and log in as that user
     -h                    this ;-)
+    --kargs               Append kernel arguments to first boot (ephemeral)
     --uefi                Boot using uefi (x86_64 only, implied on arm)
     --uefi-secure         Boot using uefi with secure boot enabled (x86_64/arm only)
 
@@ -91,6 +93,9 @@ while [ $# -ge 1 ]; do
         --uefi-secure)
             FIRMWARE=uefi-secure
             shift ;;
+        --kargs)
+            KARGS="$2"
+            shift 2;;
         -h|--help)
             echo "$USAGE"
             exit ;;
@@ -275,6 +280,9 @@ esac
 if [ -n "${HOSTNAME}" ]; then
     kola_args+=("--hostname=${HOSTNAME}")
 fi
+if [ -n "${KARGS}" ]; then
+    kola_args+=("--kargs=${KARGS}")
+fi
 
 # for the metal images, there's no other way but to inject into /boot
 case "${IMAGE_TYPE}" in