snapd: allow installing the snapd snap on UC16snapd-on-uc16

3 files changed, 48 insertions, 10 deletions

diff --git a/overlord/snapstate/snapstate.go b/overlord/snapstate/snapstate.go
index 4f0902e9a4..c3e684b241 100644
--- a/overlord/snapstate/snapstate.go
+++ b/overlord/snapstate/snapstate.go
@@ -544,14 +544,6 @@ func validateFeatureFlags(st *state.State, info *snap.Info) error {
 }
 
 func checkInstallPreconditions(st *state.State, info *snap.Info, flags Flags, snapst *SnapState, deviceCtx DeviceContext) error {
-	// Check if the snapd can be installed on Ubuntu Core systems, it is
-	// always ok to install on classic
-	if info.GetType() == snap.TypeSnapd && !release.OnClassic {
-	if deviceCtx.Model().Base() == "" {
-	return fmt.Errorf("cannot install snapd snap on a model without a base snap yet")
-	}
-	}
-
	if err := validateInfoAndFlags(info, snapst, flags); err != nil {
	return err
	}
diff --git a/tests/main/ubuntu-core-snapd/task.yaml b/tests/main/ubuntu-core-snapd/task.yaml
new file mode 100644
index 0000000000..221ae86c17
--- /dev/null
+++ b/tests/main/ubuntu-core-snapd/task.yaml
@@ -0,0 +1,36 @@
+summary: Test snapd install on a UC16 system
+
+# snapd snap is already installed by default on uc18+
+systems: [ubuntu-core-16-*]
+
+execute: |
+ if [ "$SPREAD_REBOOT" = 0 ]; then
+ echo "No snapd snap is installed"
+ not snap list snapd
+ 
+ echo "Ensure the snapd snap can be installed"
+ snap install snapd
+
+ echo "And it is considered installed"
+ snap list snapd
+
+ echo "And snapd from the snap is run in the CGroup"
+ systemctl status snapd|MATCH "/snap/snapd/[0-9]+/usr/lib/snapd/snapd"
+
+ echo "And after a reboot the snapd snap is still ok"
+ REBOOT
+ elif [ "$SPREAD_REBOOT" = 1 ]; then
+ echo "still installed"
+ snap list snapd
+ echo "and running the right snapd"
+ systemctl status snapd|MATCH "/snap/snapd/[0-9]+/usr/lib/snapd/snapd"
+
+ # we cannot restore in "restore:" because there is the rsync
+ # snap running there and it will try to refresh the sytem-key
+ systemctl stop snapd.service snapd.socket
+ rm -f /etc/systemd/system/snapd.*.{service,timer,socket}
+ rm -f /etc/systemd/system/*.wants/snapd.*.{service,timer,socket}
+ systemctl daemon-reload
+ systemctl start snapd snapd.socket
+ rsync --help
+ fi
diff --git a/wrappers/core18.go b/wrappers/core18.go
index adf95e92fa..0c7c111cc8 100644
--- a/wrappers/core18.go
+++ b/wrappers/core18.go
@@ -155,6 +155,12 @@ func writeSnapdServicesOnCore(s *snap.Info, inter interacter) error {
 
	// enable/start all the new services
	for _, unit := range changed {
+	// enable is not idempotent if the symlink target switches
+	// from /lib to /etc in the multiuser-wantes.d
+	// so we need to disable first
+	if err := sysd.Disable(unit); err != nil {
+	return err
+	}
	if err := sysd.Enable(unit); err != nil {
	return err
	}
@@ -179,8 +185,12 @@ func writeSnapdServicesOnCore(s *snap.Info, inter interacter) error {
	return err
	}
	if isActive {
-	if err := sysd.Restart(unit, 5*time.Second); err != nil {
-	return err
+	// we can never restart the snapd.socket because
+	// this will also bring down snapd itself
+	if unit != "snapd.socket" {
+	if err := sysd.Restart(unit, 5*time.Second); err != nil {
+	return err
+	}
	}
	} else {
	if err := sysd.Start(unit); err != nil {