cmd/podman.persistentRunE(): Fatal linux check if no Cgroups v2

Will log and proceed on non-linux env.

Signed-off-by: Lokesh Mandvekar <lsm5@redhat.com>

cmd/podman/root.go

@@ -248,6 +248,8 @@ func setupRemoteConnection(podmanConfig *entities.PodmanConfig) string {
 func persistentPreRunE(cmd *cobra.Command, args []string) error {
 	logrus.Debugf("Called %s.PersistentPreRunE(%s)", cmd.Name(), strings.Join(os.Args, " "))
 
+	checkSupportedCgroups()
+
 	// Help, completion and commands with subcommands are special cases, no need for more setup
 	// Completion cmd is used to generate the shell scripts
 	if cmd.Name() == "help" || cmd.Name() == "completion" || cmd.HasSubCommands() {

cmd/podman/root_cgroups_linux.go

@@ -0,0 +1,18 @@
+//go:build linux
+
+package main
+
+import (
+	"github.com/sirupsen/logrus"
+	"go.podman.io/common/pkg/cgroups"
+)
+
+func checkSupportedCgroups() {
+	unified, err := cgroups.IsCgroup2UnifiedMode()
+	if err != nil {
+		logrus.Fatalf("Error determining cgroups mode")
+	}
+	if !unified {
+		logrus.Fatalf("Cgroups v1 not supported")
+	}
+}

cmd/podman/root_cgroups_unsupported.go

@@ -0,0 +1,7 @@
+//go:build !linux
+
+package main
+
+func checkSupportedCgroups() {
+	// NOP on Non Linux
+}