revisions for #31 to address suggestions by @JoelColledge: rather tha…

…n retrying on a failed execution of truncating /etc/machine-id, determine if elevated privileges are needed in the shell script and use them from the get-go

internal/virter/vm.go

@@ -476,16 +476,9 @@ func (v *Virter) VMCommit(ctx context.Context, afterNotifier AfterNotifier, vmNa
 		// We want these IDs to be unique, so reset to empty.
 		err = v.VMExecShell(
 			ctx, []string{vmName},
-			&ProvisionShellStep{Script: "truncate -c -s 0 /etc/machine-id"})
+			&ProvisionShellStep{Script: "CMD='truncate -c -s 0 /etc/machine-id'; [ \"$(id -u)\" -eq 0 ] && $CMD || { ESC=$(command -v sudo || command -v doas || command -v please || echo ''); $ESC $CMD; }"})
 		if err != nil {
-			// In case the command failed because of an unprivileged user,
-			// retry with sudo before giving up.
-			err = v.VMExecShell(
-				ctx, []string{vmName},
-				&ProvisionShellStep{Script: "sudo truncate -c -s 0 /etc/machine-id"})
-			if err != nil {
-				return err
-			}
+			return err
 		}
 	}