Add two fields for images exported from containers

The original container image has some optional metadata in the
ENTRYPOINT and STOPSIGNAL fields, that could be needed later...

But these are not exported in the generic rootfs, by default.

Make it possible to pass these at runtime, for instance to
select between OpenRC and systemd - or SIGTERM and systemd.

Some drivers include their config in the rootfs, like wsl.conf.

Signed-off-by: Anders F Björklund <anders.f.bjorklund@gmail.com>

Author: afbjorklund

pkg/instance/start.go

@@ -109,6 +109,8 @@ func Prepare(ctx context.Context, inst *store.Instance) (*Prepared, error) {
 	kernel := filepath.Join(inst.Dir, filenames.Kernel)
 	kernelCmdline := filepath.Join(inst.Dir, filenames.KernelCmdline)
 	initrd := filepath.Join(inst.Dir, filenames.Initrd)
+	entrypoint := filepath.Join(inst.Dir, filenames.Entrypoint)
+	stopsignal := filepath.Join(inst.Dir, filenames.StopSignal)
 	if _, err := os.Stat(baseDisk); errors.Is(err, os.ErrNotExist) {
 		var ensuredBaseDisk bool
 		errs := make([]error, len(inst.Config.Images))
@@ -137,6 +139,18 @@ func Prepare(ctx context.Context, inst *store.Instance) (*Prepared, error) {
 					continue
 				}
 			}
+			if f.Entrypoint != nil {
+				if err := os.WriteFile(entrypoint, []byte(*f.Entrypoint), 0o644); err != nil {
+					errs[i] = err
+					continue
+				}
+			}
+			if f.Stopsignal != nil {
+				if err := os.WriteFile(stopsignal, []byte(*f.Stopsignal), 0o644); err != nil {
+					errs[i] = err
+					continue
+				}
+			}
 			ensuredBaseDisk = true
 			break
 		}

pkg/limayaml/limayaml.go

@@ -137,9 +137,11 @@ type Kernel struct {
 }
 
 type Image struct {
-	File   `yaml:",inline"`
-	Kernel *Kernel `yaml:"kernel,omitempty" json:"kernel,omitempty"`
-	Initrd *File   `yaml:"initrd,omitempty" json:"initrd,omitempty"`
+	File       `yaml:",inline"`
+	Kernel     *Kernel `yaml:"kernel,omitempty" json:"kernel,omitempty"`
+	Initrd     *File   `yaml:"initrd,omitempty" json:"initrd,omitempty"`
+	Entrypoint *string `yaml:"entrypoint,omitempty" json:"entrypoint,omitempty"`
+	Stopsignal *string `yaml:"stopsignal,omitempty" json:"stopsignal,omitempty"`
 }
 
 type Disk struct {

pkg/store/filenames/filenames.go

@@ -41,6 +41,8 @@ const (
 	Kernel                  = "kernel"
 	KernelCmdline           = "kernel.cmdline"
 	Initrd                  = "initrd"
+	Entrypoint              = "entrypoint"
+	StopSignal              = "stopsignal"
 	QMPSock                 = "qmp.sock"
 	SerialLog               = "serial.log" // default serial (ttyS0, but ttyAMA0 on qemu-system-{arm,aarch64})
 	SerialSock              = "serial.sock"

website/content/en/docs/dev/internals.md

@@ -52,6 +52,10 @@ kernel:
 - `kernel.cmdline`: the kernel cmdline
 - `initrd`: the initrd
 
+container:
+- `entrypoint`: the entrypoint to use (optional)
+- `stopsignal`: the stopsignal to use (optional)
+
 QEMU:
 - `qemu.pid`: QEMU PID
 - `qmp.sock`: QMP socket