Reduce complexity of install D-Bus function

Signed-off-by: Kate Goldenring <kate.goldenring@fermyon.com>

Author: kate-goldenring

internal/containerd/install_dbus.go

@@ -7,12 +7,9 @@ import (
 	"os/exec"
 )
 
-// UsesSystemd checks if the system is using systemd
-// by running the "systemctl is-system-running" command.
-// NOTE: this limits support to systems using systemctl to manage systemd
+// UsesSystemd checks if the system is using systemd.
 func UsesSystemd() bool {
-	// Check if is a systemd system
-	cmd := nsenterCmd("systemctl", "is-system-running", "--quiet")
+	cmd := nsenterCmd("systemctl", "list-units", "|", "grep", "-q", "containerd.service")
 	if err := cmd.Run(); err != nil {
 		slog.Info("Error with systemctl: %w\n", "error", err)
 		return false
@@ -30,37 +27,32 @@ func InstallDbus() error {
 		return nil
 	}
 	slog.Info("installing D-Bus")
-	whichApt := nsenterCmd("which", "apt-get")
-	whichYum := nsenterCmd("which", "yum")
-	whichDnf := nsenterCmd("which", "dnf")
-	whichApk := nsenterCmd("which", "apk")
-	if err := whichApt.Run(); err == nil {
-		cmd = nsenterCmd("apt-get", "update", "--yes")
-		if err := cmd.Run(); err != nil {
-			return fmt.Errorf("failed to update apt: %w", err)
-		}
-		cmd = nsenterCmd("apt-get", "install", "--yes", "dbus")
-		if err := cmd.Run(); err != nil {
-			return fmt.Errorf("failed to install D-Bus with apt: %w", err)
-		}
-	} else if err = whichDnf.Run(); err == nil {
-		cmd = nsenterCmd("dnf", "install", "--yes", "dbus")
-		if err := cmd.Run(); err != nil {
-			return fmt.Errorf("failed to install D-Bus with dnf: %w", err)
-		}
-	} else if err = whichApk.Run(); err == nil {
-		cmd = nsenterCmd("apk", "add", "dbus")
-		if err := cmd.Run(); err != nil {
-			return fmt.Errorf("failed to install D-Bus with apk: %w", err)
-		}
-	} else if err = whichYum.Run(); err == nil {
-		cmd = nsenterCmd("yum", "install", "--yes", "dbus")
-		if err := cmd.Run(); err != nil {
-			return fmt.Errorf("failed to install D-Bus with yum: %w", err)
+
+	type pkgManager struct {
+		name    string
+		check   []string
+		install []string
+	}
+
+	managers := []pkgManager{
+		{"apt-get", []string{"which", "apt-get"}, []string{"apt-get", "update", "--yes", "&&", "apt-get", "install", "--yes", "dbus"}},
+		{"dnf", []string{"which", "dnf"}, []string{"dnf", "install", "--yes", "dbus"}},
+		{"apk", []string{"which", "apk"}, []string{"apk", "add", "dbus"}},
+		{"yum", []string{"which", "yum"}, []string{"yum", "install", "--yes", "dbus"}},
+	}
+	installed := false
+	for _, mgr := range managers {
+		if err := nsenterCmd(mgr.check...).Run(); err == nil {
+			if err := nsenterCmd(mgr.install...).Run(); err != nil {
+				return fmt.Errorf("failed to install D-Bus with %s: %w", mgr.name, err)
+			}
+			installed = true
+			break
 		}
-	} else {
-		slog.Info("WARNING: Could not install D-Bus. No supported package manager found.")
-		return nil
+	}
+
+	if !installed {
+		return fmt.Errorf("could not install D-Bus as no supported package manager found")
 	}
 
 	slog.Info("restarting D-Bus")