Merge pull request containers#21312 from albertofaria/no-entrypoint

Allow passing the OCI runtime an empty command

pkg/specgen/generate/container_create.go

@@ -226,10 +226,7 @@ func MakeContainer(ctx context.Context, rt *libpod.Runtime, s *specgen.SpecGener
 		options = append(options, libpod.WithHostUsers(s.HostUsers))
 	}
 
-	command, err := makeCommand(s, imageData)
-	if err != nil {
-		return nil, nil, nil, err
-	}
+	command := makeCommand(s, imageData)
 
 	infraVol := len(compatibleOptions.Mounts) > 0 || len(compatibleOptions.Volumes) > 0 || len(compatibleOptions.ImageVolumes) > 0 || len(compatibleOptions.OverlayVolumes) > 0
 	opts, err := createContainerOptions(rt, s, pod, finalVolumes, finalOverlays, imageData, command, infraVol, *compatibleOptions)

pkg/specgen/generate/oci.go

@@ -3,13 +3,13 @@
 package generate
 
 import (
-	"fmt"
 	"strings"
 
 	"github.com/containers/common/libimage"
 	"github.com/containers/podman/v4/libpod/define"
 	"github.com/containers/podman/v4/pkg/specgen"
 	"github.com/opencontainers/runtime-tools/generate"
+	"github.com/sirupsen/logrus"
 )
 
 func addRlimits(s *specgen.SpecGenerator, g *generate.Generator) {
@@ -23,7 +23,7 @@ func addRlimits(s *specgen.SpecGenerator, g *generate.Generator) {
 }
 
 // Produce the final command for the container.
-func makeCommand(s *specgen.SpecGenerator, imageData *libimage.ImageData) ([]string, error) {
+func makeCommand(s *specgen.SpecGenerator, imageData *libimage.ImageData) []string {
 	finalCommand := []string{}
 
 	entrypoint := s.Entrypoint
@@ -46,13 +46,14 @@ func makeCommand(s *specgen.SpecGenerator, imageData *libimage.ImageData) ([]str
 	finalCommand = append(finalCommand, command...)
 
 	if len(finalCommand) == 0 {
-		return nil, fmt.Errorf("no command or entrypoint provided, and no CMD or ENTRYPOINT from image")
+		logrus.Debug("no command or entrypoint provided, and no CMD or ENTRYPOINT from image: defaulting to empty string")
+		finalCommand = []string{""}
 	}
 
 	if s.Init {
 		// bind mount for this binary is added in addContainerInitBinary()
 		finalCommand = append([]string{define.ContainerInitPath, "--"}, finalCommand...)
 	}
 
-	return finalCommand, nil
+	return finalCommand
 }

test/e2e/run_entrypoint_test.go

@@ -17,7 +17,7 @@ CMD []
 		podmanTest.BuildImage(dockerfile, "foobar.com/entrypoint:latest", "false")
 		session := podmanTest.Podman([]string{"run", "foobar.com/entrypoint:latest"})
 		session.WaitWithDefaultTimeout()
-		Expect(session).Should(Exit(125))
+		Expect(session).Should(Or(Exit(126), Exit(127)))
 	})
 
 	It("podman run entrypoint == [\"\"]", func() {

test/system/030-run.bats

@@ -1415,4 +1415,20 @@ search               | $IMAGE           |
     run_podman rmi $(pause_image)
 }
 
+@test "podman run - no entrypoint" {
+    run_podman 127 run --rm --rootfs "$PODMAN_TMPDIR"
+
+    # runc and crun emit different diagnostics
+    runtime=$(podman_runtime)
+    case "$runtime" in
+        crun) expect='crun: executable file `` not found in $PATH: No such file or directory: OCI runtime attempted to invoke a command that was not found' ;;
+        runc) expect='runc: runc create failed: unable to start container process: exec: "": executable file not found in $PATH: OCI runtime attempted to invoke a command that was not found' ;;
+        *)    skip "Unknown runtime '$runtime'" ;;
+    esac
+
+    # The '.*' in the error below is for dealing with podman-remote, which
+    # includes "error preparing container <sha> for attach" in output.
+    is "$output" "Error.*: $expect" "podman emits useful diagnostic when no entrypoint is set"
+}
+
 # vim: filetype=sh