improve error reporting on command execution

Author: plaffitt

iscsi/iscsi.go

@@ -2,6 +2,7 @@ package iscsi
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -482,10 +483,10 @@ func GetISCSIDevices(devicePaths []string) (devices []Device, err error) {
 
 // lsblk execute the lsblk commands
 func lsblk(flags string, devicePaths []string) ([]byte, error) {
-	out, err := exec.Command("lsblk", append([]string{flags}, devicePaths...)...).Output()
+	out, err := exec.Command("lsblk", append([]string{flags}, devicePaths...)...).CombinedOutput()
 	debug.Printf("lsblk %s %s", flags, strings.Join(devicePaths, " "))
 	if err != nil {
-		return nil, fmt.Errorf("lsblk: %v", err)
+		return nil, fmt.Errorf("lsblk: %s", string(out))
 	}
 
 	return out, nil
@@ -518,10 +519,10 @@ func RemoveSCSIDevices(devices ...Device) error {
 	var errs []error
 	for _, device := range devices {
 		debug.Printf("Flush SCSI device %v.\n", device.Name)
-		err := exec.Command("blockdev", "--flushbufs", device.GetPath()).Run()
+		out, err := exec.Command("blockdev", "--flushbufs", device.GetPath()).CombinedOutput()
 		if err != nil {
 			debug.Printf("Command 'blockdev --flushbufs %v' did not succeed to flush the device: %v\n", device.Name, err)
-			return err
+			return errors.New(string(out))
 		}
 
 		debug.Printf("Put SCSI device %v offline.\n", device.Name)

iscsi/multipath.go

@@ -3,8 +3,10 @@ package iscsi
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"os"
 	"os/exec"
+	"strings"
 	"time"
 )
 
@@ -50,7 +52,10 @@ func ExecWithTimeout(command string, args []string, timeout time.Duration) ([]by
 	}
 
 	if err != nil {
-		debug.Printf("Non-zero exit code: %s\n", err)
+		if ee, ok := err.(*exec.ExitError); ok {
+			debug.Printf("Non-zero exit code: %s\n", err)
+			err = fmt.Errorf("%s", ee.Stderr)
+		}
 	}
 
 	debug.Println("Finished executing command.")
@@ -61,10 +66,10 @@ func getMultipathMap(device string) (*multipathDeviceMap, error) {
 	debug.Printf("Getting multipath map for device %s.\n", device)
 
 	cmd := exec.Command("multipathd", "show", "map", device[1:], "json")
-	out, err := cmd.Output()
+	out, err := cmd.CombinedOutput()
 	// debug.Printf(string(out))
 	if err != nil {
-		debug.Printf("An error occured while looking for multipath device map: %v\n", err)
+		debug.Printf("An error occured while looking for multipath device map: %s\n", out)
 		return nil, err
 	}
 
@@ -100,6 +105,9 @@ func FlushMultipathDevice(device *Device) error {
 		if _, e := os.Stat(devicePath); os.IsNotExist(e) {
 			debug.Printf("Multipath device %v has been removed.\n", devicePath)
 		} else {
+			if strings.Contains(err.Error(), "map in use") {
+				err = fmt.Errorf("device is probably still in use somewhere else: %v", err)
+			}
 			debug.Printf("Command 'multipath -f %v' did not succeed to delete the device: %v\n", devicePath, err)
 			return err
 		}