sefltest: advise reboot into 4.4 on trusty running 3.13

This patch extends the self-test system to check if a user running
Ubuntu 14.04 has just installed snapd and is still running the 3.13
kernel that is used by trusty by default.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

selftest/export_test.go

@@ -20,7 +20,8 @@
 package selftest
 
 var (
-	TrySquashfsMount = trySquashfsMount
+	TrySquashfsMount   = trySquashfsMount
+	CheckKernelVersion = checkKernelVersion
 )
 
 func MockChecks(mockChecks []func() error) (restore func()) {

selftest/version.go

@@ -0,0 +1,38 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2018 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package selftest
+
+import (
+	"fmt"
+
+	"github.com/snapcore/snapd/release"
+	"github.com/snapcore/snapd/strutil"
+)
+
+// checkKernelVersion looks for some unsupported configurations that users may
+// encounter and provides advice on how to resolve them.
+func checkKernelVersion() error {
+	if release.OnClassic && release.ReleaseInfo.ID == "ubuntu" && release.ReleaseInfo.VersionID == "14.04" {
+		if cmp, _ := strutil.VersionCompare(release.KernelVersion(), "3.13"); cmp <= 0 {
+			return fmt.Errorf("you need to reboot into a 4.4 kernel to start using snapd")
+		}
+	}
+	return nil
+}

selftest/version_test.go

@@ -0,0 +1,45 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2018 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package selftest_test
+
+import (
+	. "gopkg.in/check.v1"
+
+	"github.com/snapcore/snapd/release"
+	"github.com/snapcore/snapd/selftest"
+)
+
+type versionSuite struct{}
+
+var _ = Suite(&versionSuite{})
+
+func (s *selftestSuite) TestFreshInstallOfSnapdOnTrusty(c *C) {
+	// Mock an Ubuntu 14.04 system running a 3.13 kernel
+	restore := release.MockOnClassic(true)
+	defer restore()
+	restore = release.MockReleaseInfo(&release.OS{ID: "ubuntu", VersionID: "14.04"})
+	defer restore()
+	restore = release.MockKernelVersion("3.13.0-35-generic")
+	defer restore()
+
+	// Check for the given advice.
+	err := selftest.CheckKernelVersion()
+	c.Assert(err, ErrorMatches, "you need to reboot into a 4.4 kernel to start using snapd")
+}