Support default platform via containers.conf and CONTAINER_DEFAULT_PLATFORM

cmd/podman/containers/create.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/containers/buildah/pkg/cli"
+	"github.com/containers/buildah/pkg/parse"
 	"github.com/containers/podman/v6/cmd/podman/common"
 	"github.com/containers/podman/v6/cmd/podman/registry"
 	"github.com/containers/podman/v6/cmd/podman/utils"
@@ -352,11 +353,13 @@ func pullImage(cmd *cobra.Command, imageName string, cliVals *entities.Container
 			if cliVals.Arch != "" || cliVals.OS != "" {
 				return "", errors.New("--platform option can not be specified with --arch or --os")
 			}
-			OS, Arch, hasArch := strings.Cut(cliVals.Platform, "/")
-			cliVals.OS = OS
-			if hasArch {
-				cliVals.Arch = Arch
+			pOS, pArch, pVariant, pErr := parse.Platform(cliVals.Platform)
+			if pErr != nil {
+				return "", fmt.Errorf("parsing platform %q: %w", cliVals.Platform, pErr)
 			}
+			cliVals.OS = pOS
+			cliVals.Arch = pArch
+			cliVals.Variant = pVariant
 		}
 	}
 

cmd/podman/images/pull.go

@@ -4,9 +4,9 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"strings"
 
 	"github.com/containers/buildah/pkg/cli"
+	"github.com/containers/buildah/pkg/parse"
 	"github.com/containers/podman/v6/cmd/podman/common"
 	"github.com/containers/podman/v6/cmd/podman/registry"
 	"github.com/containers/podman/v6/cmd/podman/utils"
@@ -188,13 +188,9 @@ func imagePull(cmd *cobra.Command, args []string) error {
 			return errors.New("--platform option can not be specified with --arch or --os")
 		}
 
-		specs := strings.Split(platform, "/")
-		pullOptions.OS = specs[0] // may be empty
-		if len(specs) > 1 {
-			pullOptions.Arch = specs[1]
-			if len(specs) > 2 {
-				pullOptions.Variant = specs[2]
-			}
+		pullOptions.OS, pullOptions.Arch, pullOptions.Variant, err = parse.Platform(platform)
+		if err != nil {
+			return fmt.Errorf("parsing platform %q: %w", platform, err)
 		}
 	}
 

docs/source/markdown/options/platform.md

@@ -7,3 +7,8 @@
 Specify the platform for selecting the image.  (Conflicts with --arch and --os)
 The `--platform` option can be used to override the current architecture and operating system.
 Unless overridden, subsequent lookups of the same image in the local storage matches this platform, regardless of the host.
+
+If not specified, the default platform is resolved in the following order:
+1. The **CONTAINER_DEFAULT_PLATFORM** environment variable.
+2. The **platform** setting in **containers.conf**(5).
+3. The host's native OS/architecture.

docs/source/markdown/podman-build.1.md.in

@@ -319,6 +319,11 @@ architecture of the host (for example `linux/arm`).  Unless overridden,
 subsequent lookups of the same image in the local storage matches this
 platform, regardless of the host.
 
+If not specified, the default platform is resolved in the following order:
+1. The **CONTAINER_DEFAULT_PLATFORM** environment variable.
+2. The **platform** setting in **containers.conf**(5).
+3. The host's native OS/architecture.
+
 If `--platform` is set, then the values of the `--arch`, `--os`, and
 `--variant` options is overridden.
 

pkg/api/handlers/compat/containers_create.go

@@ -24,6 +24,7 @@ import (
 	"github.com/containers/podman/v6/pkg/rootless"
 	"github.com/containers/podman/v6/pkg/specgen"
 	"github.com/containers/podman/v6/pkg/specgenutil"
+	"github.com/containers/podman/v6/pkg/util"
 	"github.com/docker/docker/api/types/mount"
 	"go.podman.io/common/libimage"
 	"go.podman.io/common/libnetwork/types"
@@ -74,13 +75,25 @@ func CreateContainer(w http.ResponseWriter, r *http.Request) {
 	body.Config.Image = imageName
 
 	lookupImageOptions := libimage.LookupImageOptions{}
-	if query.Platform != "" {
+	// If no platform was specified in the query, fall back to
+	// CONTAINER_DEFAULT_PLATFORM env var, then containers.conf platform.
+	platform := query.Platform
+	if platform != "" {
 		var err error
-		lookupImageOptions.OS, lookupImageOptions.Architecture, lookupImageOptions.Variant, err = parse.Platform(query.Platform)
+		lookupImageOptions.OS, lookupImageOptions.Architecture, lookupImageOptions.Variant, err = parse.Platform(platform)
 		if err != nil {
 			utils.Error(w, http.StatusBadRequest, fmt.Errorf("parsing platform: %w", err))
 			return
 		}
+	} else {
+		defOS, defArch, defVariant, err := util.DefaultPlatform(rtc.Engine.Platform)
+		if err != nil {
+			utils.Error(w, http.StatusBadRequest, err)
+			return
+		}
+		lookupImageOptions.OS = defOS
+		lookupImageOptions.Architecture = defArch
+		lookupImageOptions.Variant = defVariant
 	}
 	newImage, resolvedName, err := runtime.LibimageRuntime().LookupImage(body.Config.Image, &lookupImageOptions)
 	if err != nil {

pkg/api/handlers/compat/images.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/containers/buildah"
+	"github.com/containers/buildah/pkg/parse"
 	"github.com/containers/podman/v6/libpod"
 	"github.com/containers/podman/v6/pkg/api/handlers"
 	"github.com/containers/podman/v6/pkg/api/handlers/utils"
@@ -222,16 +223,37 @@ func CreateImageFromSrc(w http.ResponseWriter, r *http.Request) {
 		reference = possiblyNormalizedName
 	}
 
-	platformSpecs := strings.Split(query.Platform, "/")
-	opts := entities.ImageImportOptions{
-		Source:    source,
-		Changes:   query.Changes,
-		Message:   query.Message,
-		Reference: reference,
-		OS:        platformSpecs[0],
+	// If no platform was specified in the query, fall back to
+	// CONTAINER_DEFAULT_PLATFORM env var, then containers.conf platform.
+	var platOS, platArch, platVariant string
+	if query.Platform != "" {
+		var pErr error
+		platOS, platArch, platVariant, pErr = parse.Platform(query.Platform)
+		if pErr != nil {
+			utils.Error(w, http.StatusBadRequest, fmt.Errorf("parsing platform: %w", pErr))
+			return
+		}
+	} else {
+		rtc, err := runtime.GetConfig()
+		confPlatform := ""
+		if err == nil {
+			confPlatform = rtc.Engine.Platform
+		}
+		var pErr error
+		platOS, platArch, platVariant, pErr = util.DefaultPlatform(confPlatform)
+		if pErr != nil {
+			utils.Error(w, http.StatusBadRequest, pErr)
+			return
+		}
 	}
-	if len(platformSpecs) > 1 {
-		opts.Architecture = platformSpecs[1]
+	opts := entities.ImageImportOptions{
+		Source:       source,
+		Changes:      query.Changes,
+		Message:      query.Message,
+		Reference:    reference,
+		OS:           platOS,
+		Architecture: platArch,
+		Variant:      platVariant,
 	}
 
 	imageEngine := abi.ImageEngine{Libpod: runtime}
@@ -310,12 +332,26 @@ func CreateImageFromImage(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Handle the platform.
-	platformSpecs := strings.Split(query.Platform, "/")
-	pullOptions.OS = platformSpecs[0] // may be empty
-	if len(platformSpecs) > 1 {
-		pullOptions.Architecture = platformSpecs[1]
-		if len(platformSpecs) > 2 {
-			pullOptions.Variant = platformSpecs[2]
+	// If no platform was specified in the query, fall back to
+	// CONTAINER_DEFAULT_PLATFORM env var, then containers.conf platform.
+	if query.Platform != "" {
+		var pErr error
+		pullOptions.OS, pullOptions.Architecture, pullOptions.Variant, pErr = parse.Platform(query.Platform)
+		if pErr != nil {
+			utils.Error(w, http.StatusBadRequest, fmt.Errorf("parsing platform: %w", pErr))
+			return
+		}
+	} else {
+		rtc, err := runtime.GetConfig()
+		confPlatform := ""
+		if err == nil {
+			confPlatform = rtc.Engine.Platform
+		}
+		var pErr error
+		pullOptions.OS, pullOptions.Architecture, pullOptions.Variant, pErr = util.DefaultPlatform(confPlatform)
+		if pErr != nil {
+			utils.Error(w, http.StatusBadRequest, pErr)
+			return
 		}
 	}
 

pkg/api/handlers/compat/images_build.go

@@ -776,20 +776,39 @@ func createBuildOptions(query *BuildQuery, buildCtx *BuildContext, queryValues u
 
 	// Process platforms
 	platforms := query.Platform
-	if len(platforms) == 1 {
-		// Docker API uses comma separated platform arg so match this here
-		platforms = strings.Split(query.Platform[0], ",")
-	}
-	for _, platformSpec := range platforms {
-		os, arch, variant, err := parse.Platform(platformSpec)
-		if err != nil {
-			return nil, cleanup, utils.GetBadRequestError("platform", platformSpec, err)
+	if len(platforms) == 0 || (len(platforms) == 1 && platforms[0] == "") {
+		// No explicit platform specified; fall back to
+		// CONTAINER_DEFAULT_PLATFORM env var, then containers.conf platform.
+		runtime := r.Context().Value(api.RuntimeKey).(*libpod.Runtime)
+		confPlatform := ""
+		if rtc, err := runtime.GetConfigNoCopy(); err == nil {
+			confPlatform = rtc.Engine.Platform
+		}
+		defOS, defArch, defVariant, pErr := util.DefaultPlatform(confPlatform)
+		if pErr != nil {
+			return nil, cleanup, utils.GetBadRequestError("platform", confPlatform, pErr)
+		}
+		if defOS != "" || defArch != "" || defVariant != "" {
+			buildOptions.Platforms = append(buildOptions.Platforms, struct{ OS, Arch, Variant string }{
+				OS: defOS, Arch: defArch, Variant: defVariant,
+			})
+		}
+	} else {
+		if len(platforms) == 1 {
+			// Docker API uses comma separated platform arg so match this here
+			platforms = strings.Split(platforms[0], ",")
+		}
+		for _, platformSpec := range platforms {
+			os, arch, variant, err := parse.Platform(platformSpec)
+			if err != nil {
+				return nil, cleanup, utils.GetBadRequestError("platform", platformSpec, err)
+			}
+			buildOptions.Platforms = append(buildOptions.Platforms, struct{ OS, Arch, Variant string }{
+				OS:      os,
+				Arch:    arch,
+				Variant: variant,
+			})
 		}
-		buildOptions.Platforms = append(buildOptions.Platforms, struct{ OS, Arch, Variant string }{
-			OS:      os,
-			Arch:    arch,
-			Variant: variant,
-		})
 	}
 
 	// Process source policy

pkg/api/handlers/libpod/images_pull.go

@@ -16,6 +16,7 @@ import (
 	"github.com/containers/podman/v6/pkg/auth"
 	"github.com/containers/podman/v6/pkg/channel"
 	"github.com/containers/podman/v6/pkg/domain/entities"
+	"github.com/containers/podman/v6/pkg/util"
 	"github.com/gorilla/schema"
 	"github.com/sirupsen/logrus"
 	"go.podman.io/common/libimage"
@@ -75,6 +76,23 @@ func ImagesPull(w http.ResponseWriter, r *http.Request) {
 	pullOptions.OS = query.OS
 	pullOptions.Variant = query.Variant
 
+	// If no explicit platform fields were given, fall back to
+	// CONTAINER_DEFAULT_PLATFORM env var, then containers.conf platform.
+	if query.Arch == "" && query.OS == "" && query.Variant == "" {
+		confPlatform := ""
+		if rtc, err := runtime.GetConfig(); err == nil {
+			confPlatform = rtc.Engine.Platform
+		}
+		defOS, defArch, defVariant, pErr := util.DefaultPlatform(confPlatform)
+		if pErr != nil {
+			utils.Error(w, http.StatusBadRequest, pErr)
+			return
+		}
+		pullOptions.OS = defOS
+		pullOptions.Architecture = defArch
+		pullOptions.Variant = defVariant
+	}
+
 	if _, found := r.URL.Query()["tlsVerify"]; found {
 		pullOptions.InsecureSkipTLSVerify = types.NewOptionalBool(!query.TLSVerify)
 	}

pkg/domain/infra/abi/images.go

@@ -27,6 +27,7 @@ import (
 	domainUtils "github.com/containers/podman/v6/pkg/domain/utils"
 	"github.com/containers/podman/v6/pkg/errorhandling"
 	"github.com/containers/podman/v6/pkg/rootless"
+	"github.com/containers/podman/v6/pkg/util"
 	"github.com/opencontainers/go-digest"
 	imgspecv1 "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/sirupsen/logrus"
@@ -282,6 +283,22 @@ func (ir *ImageEngine) Unmount(ctx context.Context, nameOrIDs []string, options
 }
 
 func (ir *ImageEngine) Pull(ctx context.Context, rawImage string, options entities.ImagePullOptions) (*entities.ImagePullReport, error) {
+	// If no explicit platform was requested, fall back to
+	// containers.conf [engine] platform (resolved server-side).
+	if options.Arch == "" && options.OS == "" && options.Variant == "" {
+		rtc, err := ir.Libpod.GetConfigNoCopy()
+		if err != nil {
+			return nil, err
+		}
+		defOS, defArch, defVariant, err := util.DefaultPlatform(rtc.Engine.Platform)
+		if err != nil {
+			return nil, err
+		}
+		options.OS = defOS
+		options.Arch = defArch
+		options.Variant = defVariant
+	}
+
 	pullOptions := &libimage.PullOptions{AllTags: options.AllTags}
 	pullOptions.AuthFilePath = options.Authfile
 	pullOptions.CertDirPath = options.CertDir
@@ -512,6 +529,22 @@ func (ir *ImageEngine) Save(ctx context.Context, nameOrID string, tags []string,
 }
 
 func (ir *ImageEngine) Import(ctx context.Context, options entities.ImageImportOptions) (*entities.ImageImportReport, error) {
+	// If no explicit platform was requested, fall back to
+	// containers.conf [engine] platform (resolved server-side).
+	if options.OS == "" && options.Architecture == "" && options.Variant == "" {
+		rtc, err := ir.Libpod.GetConfigNoCopy()
+		if err != nil {
+			return nil, err
+		}
+		defOS, defArch, defVariant, err := util.DefaultPlatform(rtc.Engine.Platform)
+		if err != nil {
+			return nil, err
+		}
+		options.OS = defOS
+		options.Architecture = defArch
+		options.Variant = defVariant
+	}
+
 	importOptions := &libimage.ImportOptions{}
 	importOptions.Changes = options.Changes
 	importOptions.CommitMessage = options.Message
@@ -581,6 +614,24 @@ func (ir *ImageEngine) Config(_ context.Context) (*config.Config, error) {
 }
 
 func (ir *ImageEngine) Build(ctx context.Context, containerFiles []string, opts entities.BuildOptions) (*entities.BuildReport, error) {
+	// If no explicit platform was requested, fall back to
+	// containers.conf [engine] platform (resolved server-side).
+	if len(opts.Platforms) == 0 {
+		rtc, err := ir.Libpod.GetConfigNoCopy()
+		if err != nil {
+			return nil, err
+		}
+		defOS, defArch, defVariant, err := util.DefaultPlatform(rtc.Engine.Platform)
+		if err != nil {
+			return nil, err
+		}
+		if defOS != "" || defArch != "" || defVariant != "" {
+			opts.Platforms = append(opts.Platforms, struct{ OS, Arch, Variant string }{
+				OS: defOS, Arch: defArch, Variant: defVariant,
+			})
+		}
+	}
+
 	id, _, err := ir.Libpod.Build(ctx, opts.BuildOptions, containerFiles...)
 	if err != nil {
 		return nil, err

pkg/util/utils.go

@@ -16,6 +16,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/containers/buildah/pkg/parse"
 	"github.com/containers/podman/v6/libpod/define"
 	"github.com/containers/podman/v6/pkg/namespaces"
 	"github.com/containers/podman/v6/pkg/rootless"
@@ -143,6 +144,28 @@ func ParseRegistryCreds(creds string) (*types.DockerAuthConfig, error) {
 	}, nil
 }
 
+// DefaultPlatform returns the default platform (platOS, arch, variant) from
+// the CONTAINER_DEFAULT_PLATFORM environment variable or the given
+// containers.conf Engine.Platform value.  The confPlatform parameter should
+// be the caller's config.Engine.Platform string.  If neither source provides
+// a value, empty strings and a nil error are returned.  The platform string
+// is always parsed through buildah's parse.Platform() so that validation and
+// normalisation are consistent across all call sites.
+func DefaultPlatform(confPlatform string) (platOS, arch, variant string, err error) {
+	platform, ok := os.LookupEnv("CONTAINER_DEFAULT_PLATFORM")
+	if !ok || platform == "" {
+		platform = confPlatform
+	}
+	if platform == "" {
+		return "", "", "", nil
+	}
+	platOS, arch, variant, err = parse.Platform(platform)
+	if err != nil {
+		return "", "", "", fmt.Errorf("parsing default platform %q: %w", platform, err)
+	}
+	return platOS, arch, variant, nil
+}
+
 // StringMatchRegexSlice determines if a given string matches one of the given regexes, returns bool
 func StringMatchRegexSlice(s string, re []string) bool {
 	for _, r := range re {