log mkfs.ext4 stderr output (#2474)

anmaxvl · web-flow · commit 1c0e46403dc0 · 2025-07-10T12:01:04.000-07:00
Log the stderr output when `mkfs.ext4` fails during scratch formatting.
This should help troubleshooting easier, e.g. when the binary is missing
or not properly symlinked etc.

Signed-off-by: Maksim An &lt;maksiman@microsoft.com&gt;
diff --git a/internal/lcow/scratch.go b/internal/lcow/scratch.go
@@ -105,6 +105,7 @@ func CreateScratch(ctx context.Context, lcowUVM *uvm.UtilityVM, destFile string,
 	err = cmd.Run()
 	cancel()
 	if err != nil {
+		log.G(ctx).WithError(err).WithField("stderr", mkfsStderr.String()).Error("mkfs.ext4 failed")
 		return fmt.Errorf("failed to `%+v` following hot-add %s to utility VM: %w", cmd.Spec.Args, destFile, err)
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -105,6 +105,7 @@ func CreateScratch(ctx context.Context, lcowUVM *uvm.UtilityVM, destFile string,`
`105`	`105`	`err = cmd.Run()`
`106`	`106`	`cancel()`
`107`	`107`	`if err != nil {`
	`108`	`+ log.G(ctx).WithError(err).WithField("stderr", mkfsStderr.String()).Error("mkfs.ext4 failed")`
`108`	`109`	return fmt.Errorf("failed to `%+v` following hot-add %s to utility VM: %w", cmd.Spec.Args, destFile, err)
`109`	`110`	`}`
`110`	`111`