experiment: adding pre-built snapd to classic images

snapdtool/tool_linux.go

@@ -211,9 +211,11 @@ func ExecInSnapdOrCoreSnap() {
 
 	// Is this executable in the core snap too?
 	coreOrSnapdPath := snapdSnap
+	origin := "snapd from snap"
 	full := filepath.Join(snapdSnap, exe)
 	if !osutil.FileExists(full) {
 		coreOrSnapdPath = coreSnap
+		origin = "snapd from core"
 		full = filepath.Join(coreSnap, exe)
 		if !osutil.FileExists(full) {
 			return
@@ -222,9 +224,10 @@ func ExecInSnapdOrCoreSnap() {
 
 	// If the core snap doesn't support re-exec or run-from-core then don't do it.
 	if !systemSnapSupportsReExec(coreOrSnapdPath) {
+		logger.Noticef(">>>>>> %s does not support re-exec", origin)
 		return
 	}
-
+	logger.Noticef(">>>>>>> restarting into %s (%q)", origin, full)
 	logger.Debugf("restarting into %q", full)
 	panic(syscallExec(full, os.Args, os.Environ()))
 }

tests/lib/prepare.sh

@@ -412,6 +412,29 @@ prepare_classic() {
             cache_snaps core20
         fi
 
+        # Install snapd either build by CI or by snapcraft depending on
+        # TESTS_USE_PREBUILT_SNAPD_SNAP. This makes the default behaviour
+        # to re-exec to snapd snap instead of snapd in core. Furthermore,
+        # it prevents snapd from automatically installing snapd snap as
+        # prerequisite for installing any non-base snap
+        if snap list snapd ; then
+	    snap snap info snapd
+	    echo "Error: not expecting snapd be be installed"
+	    exit 1
+	else
+	    echo ">>>>>> Snapd is not installed"
+	    echo ">>>>>> Building snapd"
+            build_dir="$WORK_DIR/snapd_snap_for_classic"
+	    rm -rf "$build_dir"
+	    mkdir -p "$build_dir"
+            build_snapd_snap "$build_dir"
+	    echo ">>>>>> Installing snapd"
+            snap install "$build_dir/"snapd_*.snap
+        fi
+        snap list | grep snapd
+
+	#exit 1
+
         # now use parameterized core channel (defaults to edge) instead
         # of a fixed one and close to stable in order to detect defects
         # earlier