From d0ae69087c46a7f863ccde2f453804e0169a570b Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Tue, 26 May 2020 09:32:33 -0700
Subject: [PATCH] fix: add proper errors for disks with preexisting content
 (#9703)

---
 cmd/config/errors.go   |  6 ++++++
 cmd/format-xl.go       | 14 ++++++++------
 cmd/prepare-storage.go |  3 ++-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/cmd/config/errors.go b/cmd/config/errors.go
index 6ae509114..7b6428e78 100644
--- a/cmd/config/errors.go
+++ b/cmd/config/errors.go
@@ -181,6 +181,12 @@ Example 1:
 		"",
 	)
 
+	ErrCorruptedBackend = newErrFn(
+		"Unable to use the specified backend, pre-existing content detected",
+		"Please ensure your disk mount does not have any pre-existing content",
+		"",
+	)
+
 	ErrUnableToWriteInBackend = newErrFn(
 		"Unable to write to the backend",
 		"Please ensure MinIO binary has write permissions for the backend",
diff --git a/cmd/format-xl.go b/cmd/format-xl.go
index 565f647e2..8d7ad9f24 100644
--- a/cmd/format-xl.go
+++ b/cmd/format-xl.go
@@ -27,6 +27,7 @@ import (
 	"sync"
 
 	humanize "github.com/dustin/go-humanize"
+	"github.com/minio/minio/cmd/config"
 	"github.com/minio/minio/cmd/config/storageclass"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/color"
@@ -379,11 +380,12 @@ func saveFormatXL(disk StorageAPI, format interface{}, diskID string) error {
 }
 
 var ignoredHiddenDirectories = map[string]struct{}{
-	minioMetaBucket:             {},
-	".snapshot":                 {},
-	"lost+found":                {},
-	"$RECYCLE.BIN":              {},
-	"System Volume Information": {},
+	minioMetaBucket:             {}, // metabucket '.minio.sys'
+	".minio":                    {}, // users may choose to double down the backend as the config folder for certs
+	".snapshot":                 {}, // .snapshot for ignoring NetApp based persistent volumes WAFL snapshot
+	"lost+found":                {}, // 'lost+found' directory default on ext4 filesystems
+	"$RECYCLE.BIN":              {}, // windows specific directory for each drive (hidden)
+	"System Volume Information": {}, // windows specific directory for each drive (hidden)
 }
 
 func isHiddenDirectories(vols ...VolInfo) bool {
@@ -499,7 +501,7 @@ func formatXLFixDeploymentID(endpoints Endpoints, storageDisks []StorageAPI, ref
 	formats, sErrs := loadFormatXLAll(storageDisks, false)
 	for i, sErr := range sErrs {
 		if _, ok := formatCriticalErrors[sErr]; ok {
-			return fmt.Errorf("Disk %s: %w", endpoints[i], sErr)
+			return config.ErrCorruptedBackend(err).Hint(fmt.Sprintf("Clear any pre-existing content on %s", endpoints[i]))
 		}
 	}
 
diff --git a/cmd/prepare-storage.go b/cmd/prepare-storage.go
index 6f8fa8c06..9c813c96e 100644
--- a/cmd/prepare-storage.go
+++ b/cmd/prepare-storage.go
@@ -27,6 +27,7 @@ import (
 	"time"
 
 	"github.com/dustin/go-humanize"
+	"github.com/minio/minio/cmd/config"
 	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/cmd/rest"
@@ -227,7 +228,7 @@ func connectLoadInitFormats(retryCount int, firstDisk bool, endpoints Endpoints,
 	// Check if we have
 	for i, sErr := range sErrs {
 		if _, ok := formatCriticalErrors[sErr]; ok {
-			return nil, nil, fmt.Errorf("Disk %s: %w", endpoints[i], sErr)
+			return nil, nil, config.ErrCorruptedBackend(err).Hint(fmt.Sprintf("Clear any pre-existing content on %s", endpoints[i]))
 		}
 		// not critical error but still print the error, nonetheless, which is perhaps unhandled
 		if sErr != errUnformattedDisk && sErr != errDiskNotFound && retryCount >= 5 {