devicestate: print some debug output when seeding failsdebug-seed-failure

When seeding fails that is a rare but catastrophic event. To help understanding these problems this commit adds some extra debug output. For now that is just the `timedatectl` output as this is the most common source of issues but we could extend it in the future. 

1 files changed, 23 insertions, 0 deletions

diff --git a/overlord/devicestate/devicemgr.go b/overlord/devicestate/devicemgr.go
index 98690d558e..0da5e8ab88 100644
--- a/overlord/devicestate/devicemgr.go
+++ b/overlord/devicestate/devicemgr.go
@@ -20,11 +20,13 @@
 package devicestate
 
 import (
+	"bytes"
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
+	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
@@ -1366,6 +1368,25 @@ func (e *ensureError) Error() string {
 // no \n allowed in warnings
 var seedFailureFmt = `seeding failed with: %v. This indicates an error in your distribution, please see https://forum.snapcraft.io/t/16341 for more information.`
 
+func debugSeedFailure(err error) string {
+	buf := bytes.NewBuffer(nil)
+
+	h1fmt := "\n==================== %s ===================="
+	h2fmt := "========== %s =========="
+
+	fmt.Fprintf(buf, h1fmt, "seeding failed")
+	fmt.Fprintf(buf, "error: %v", err)
+
+	fmt.Fprintf(buf, h2fmt, "timedatectl output")
+	output, err := exec.Command("timedatectl", "status").CombinedOutput()
+	if err != nil {
+	fmt.Fprintf(buf, "failed: %v", err)
+	}
+	fmt.Fprintf(buf, "%v", output)
+
+	return buf.String()
+}
+
 // Ensure implements StateManager.Ensure.
 func (m *DeviceManager) Ensure() error {
	var errs []error
@@ -1375,6 +1396,8 @@ func (m *DeviceManager) Ensure() error {
	m.state.Warnf(seedFailureFmt, err)
	m.state.Unlock()
	errs = append(errs, fmt.Errorf("cannot seed: %v", err))
+
+	logger.Noticef("%s", debugSeedFailure(err))
	}
 
	if !m.preseed {