chore: Bump version to 4.2.15

New 'dbbackup version' command shows:
- Build version, time, and git commit
- Go runtime version
- OS/architecture
- CPU cores
- Installed database tools (pg_dump, mysqldump, etc.)

Output formats:
- table (default): Nice ASCII table
- json: For scripting/automation
- short: Just version number

Useful for troubleshooting and bug reports.

CHANGELOG.md

@@ -5,6 +5,81 @@ All notable changes to dbbackup will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [4.2.9] - 2026-01-30
+
+### Added - MEDIUM Priority Features
+
+- **#11: Enhanced Error Diagnostics with System Context (MEDIUM priority)**
+  - Automatic environmental context collection on errors
+  - Real-time system diagnostics: disk space, memory, file descriptors
+  - PostgreSQL diagnostics: connections, locks, shared memory, version
+  - Smart root cause analysis based on error + environment
+  - Context-specific recommendations (e.g., "Disk 95% full" → cleanup commands)
+  - Comprehensive diagnostics report with actionable fixes
+  - **Problem**: Errors showed symptoms but not environmental causes
+  - **Solution**: Diagnose system state + error pattern → root cause + fix
+
+**Diagnostic Report Includes:**
+- Disk space usage and available capacity
+- Memory usage and pressure indicators
+- File descriptor utilization (Linux/Unix)
+- PostgreSQL connection pool status
+- Lock table capacity calculations
+- Version compatibility checks
+- Contextual recommendations based on actual system state
+
+**Example Diagnostics:**
+```
+═══════════════════════════════════════════════════════════
+  DBBACKUP ERROR DIAGNOSTICS REPORT
+═══════════════════════════════════════════════════════════
+
+Error Type: CRITICAL
+Category:   locks
+Severity:   2/3
+
+Message:
+  out of shared memory: max_locks_per_transaction exceeded
+
+Root Cause:
+  Lock table capacity too low (32,000 total locks). Likely cause: 
+  max_locks_per_transaction (128) too low for this database size
+
+System Context:
+  Disk Space:  45.3 GB / 100.0 GB (45.3% used)
+  Memory:      3.2 GB / 8.0 GB (40.0% used)
+  File Descriptors: 234 / 4096
+
+Database Context:
+  Version:     PostgreSQL 14.10
+  Connections: 15 / 100
+  Max Locks:   128 per transaction
+  Total Lock Capacity: ~12,800
+
+Recommendations:
+  Current lock capacity: 12,800 locks (max_locks_per_transaction × max_connections)
+  ⚠ max_locks_per_transaction is low (128)
+  • Increase: ALTER SYSTEM SET max_locks_per_transaction = 4096;
+  • Then restart PostgreSQL: sudo systemctl restart postgresql
+
+Suggested Action:
+  Fix: ALTER SYSTEM SET max_locks_per_transaction = 4096; then 
+  RESTART PostgreSQL
+```
+
+**Functions:**
+- `GatherErrorContext()` - Collects system + database metrics
+- `DiagnoseError()` - Full error analysis with environmental context
+- `FormatDiagnosticsReport()` - Human-readable report generation
+- `generateContextualRecommendations()` - Smart recommendations based on state
+- `analyzeRootCause()` - Pattern matching for root cause identification
+
+**Integration:**
+- Available for all backup/restore operations
+- Automatic context collection on critical errors
+- Can be manually triggered for troubleshooting
+- Export as JSON for automated monitoring
+
 ## [4.2.8] - 2026-01-30
 
 ### Added - MEDIUM Priority Features

cmd/catalog_export.go

@@ -0,0 +1,463 @@
+package cmd
+
+import (
+	"context"
+	"encoding/csv"
+	"encoding/json"
+	"fmt"
+	"html"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"dbbackup/internal/catalog"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	exportOutput string
+	exportFormat string
+)
+
+// catalogExportCmd exports catalog to various formats
+var catalogExportCmd = &cobra.Command{
+	Use:   "export",
+	Short: "Export catalog to file (CSV/HTML/JSON)",
+	Long: `Export backup catalog to various formats for analysis, reporting, or archival.
+
+Supports:
+  - CSV format for spreadsheet import (Excel, LibreOffice)
+  - HTML format for web-based reports and documentation
+  - JSON format for programmatic access and integration
+
+Examples:
+  # Export to CSV
+  dbbackup catalog export --format csv --output backups.csv
+
+  # Export to HTML report
+  dbbackup catalog export --format html --output report.html
+
+  # Export specific database
+  dbbackup catalog export --format csv --database myapp --output myapp_backups.csv
+
+  # Export date range
+  dbbackup catalog export --format html --after 2026-01-01 --output january_report.html`,
+	RunE: runCatalogExport,
+}
+
+func init() {
+	catalogCmd.AddCommand(catalogExportCmd)
+	catalogExportCmd.Flags().StringVarP(&exportOutput, "output", "o", "", "Output file path (required)")
+	catalogExportCmd.Flags().StringVarP(&exportFormat, "format", "f", "csv", "Export format: csv, html, json")
+	catalogExportCmd.Flags().StringVar(&catalogDatabase, "database", "", "Filter by database name")
+	catalogExportCmd.Flags().StringVar(&catalogStartDate, "after", "", "Show backups after date (YYYY-MM-DD)")
+	catalogExportCmd.Flags().StringVar(&catalogEndDate, "before", "", "Show backups before date (YYYY-MM-DD)")
+	catalogExportCmd.MarkFlagRequired("output")
+}
+
+func runCatalogExport(cmd *cobra.Command, args []string) error {
+	if exportOutput == "" {
+		return fmt.Errorf("--output flag required")
+	}
+
+	// Validate format
+	exportFormat = strings.ToLower(exportFormat)
+	if exportFormat != "csv" && exportFormat != "html" && exportFormat != "json" {
+		return fmt.Errorf("invalid format: %s (supported: csv, html, json)", exportFormat)
+	}
+
+	cat, err := openCatalog()
+	if err != nil {
+		return err
+	}
+	defer cat.Close()
+
+	ctx := context.Background()
+
+	// Build query
+	query := &catalog.SearchQuery{
+		Database:  catalogDatabase,
+		Limit:     0, // No limit - export all
+		OrderBy:   "created_at",
+		OrderDesc: false, // Chronological order for exports
+	}
+
+	// Parse dates if provided
+	if catalogStartDate != "" {
+		after, err := time.Parse("2006-01-02", catalogStartDate)
+		if err != nil {
+			return fmt.Errorf("invalid --after date format (use YYYY-MM-DD): %w", err)
+		}
+		query.StartDate = &after
+	}
+
+	if catalogEndDate != "" {
+		before, err := time.Parse("2006-01-02", catalogEndDate)
+		if err != nil {
+			return fmt.Errorf("invalid --before date format (use YYYY-MM-DD): %w", err)
+		}
+		query.EndDate = &before
+	}
+
+	// Search backups
+	entries, err := cat.Search(ctx, query)
+	if err != nil {
+		return fmt.Errorf("failed to search catalog: %w", err)
+	}
+
+	if len(entries) == 0 {
+		fmt.Println("No backups found matching criteria")
+		return nil
+	}
+
+	// Export based on format
+	switch exportFormat {
+	case "csv":
+		return exportCSV(entries, exportOutput)
+	case "html":
+		return exportHTML(entries, exportOutput, catalogDatabase)
+	case "json":
+		return exportJSON(entries, exportOutput)
+	default:
+		return fmt.Errorf("unsupported format: %s", exportFormat)
+	}
+}
+
+// exportCSV exports entries to CSV format
+func exportCSV(entries []*catalog.Entry, outputPath string) error {
+	file, err := os.Create(outputPath)
+	if err != nil {
+		return fmt.Errorf("failed to create output file: %w", err)
+	}
+	defer file.Close()
+
+	writer := csv.NewWriter(file)
+	defer writer.Flush()
+
+	// Header
+	header := []string{
+		"ID",
+		"Database",
+		"DatabaseType",
+		"Host",
+		"Port",
+		"BackupPath",
+		"BackupType",
+		"SizeBytes",
+		"SizeHuman",
+		"SHA256",
+		"Compression",
+		"Encrypted",
+		"CreatedAt",
+		"DurationSeconds",
+		"Status",
+		"VerifiedAt",
+		"VerifyValid",
+		"TestedAt",
+		"TestSuccess",
+		"RetentionPolicy",
+	}
+
+	if err := writer.Write(header); err != nil {
+		return fmt.Errorf("failed to write CSV header: %w", err)
+	}
+
+	// Data rows
+	for _, entry := range entries {
+		row := []string{
+			fmt.Sprintf("%d", entry.ID),
+			entry.Database,
+			entry.DatabaseType,
+			entry.Host,
+			fmt.Sprintf("%d", entry.Port),
+			entry.BackupPath,
+			entry.BackupType,
+			fmt.Sprintf("%d", entry.SizeBytes),
+			catalog.FormatSize(entry.SizeBytes),
+			entry.SHA256,
+			entry.Compression,
+			fmt.Sprintf("%t", entry.Encrypted),
+			entry.CreatedAt.Format(time.RFC3339),
+			fmt.Sprintf("%.2f", entry.Duration),
+			string(entry.Status),
+			formatTime(entry.VerifiedAt),
+			formatBool(entry.VerifyValid),
+			formatTime(entry.DrillTestedAt),
+			formatBool(entry.DrillSuccess),
+			entry.RetentionPolicy,
+		}
+
+		if err := writer.Write(row); err != nil {
+			return fmt.Errorf("failed to write CSV row: %w", err)
+		}
+	}
+
+	fmt.Printf("✅ Exported %d backups to CSV: %s\n", len(entries), outputPath)
+	fmt.Printf("   Open with Excel, LibreOffice, or other spreadsheet software\n")
+	return nil
+}
+
+// exportHTML exports entries to HTML format with styling
+func exportHTML(entries []*catalog.Entry, outputPath string, database string) error {
+	file, err := os.Create(outputPath)
+	if err != nil {
+		return fmt.Errorf("failed to create output file: %w", err)
+	}
+	defer file.Close()
+
+	title := "Backup Catalog Report"
+	if database != "" {
+		title = fmt.Sprintf("Backup Catalog Report: %s", database)
+	}
+
+	// Write HTML header with embedded CSS
+	htmlHeader := fmt.Sprintf(`<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>%s</title>
+    <style>
+        body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; margin: 20px; background: #f5f5f5; }
+        .container { max-width: 1400px; margin: 0 auto; background: white; padding: 30px; box-shadow: 0 2px 10px rgba(0,0,0,0.1); }
+        h1 { color: #2c3e50; border-bottom: 3px solid #3498db; padding-bottom: 10px; }
+        .summary { background: #ecf0f1; padding: 15px; margin: 20px 0; border-radius: 5px; }
+        .summary-item { display: inline-block; margin-right: 30px; }
+        .summary-label { font-weight: bold; color: #7f8c8d; }
+        .summary-value { color: #2c3e50; font-size: 18px; }
+        table { width: 100%%; border-collapse: collapse; margin-top: 20px; }
+        th { background: #34495e; color: white; padding: 12px; text-align: left; font-weight: 600; }
+        td { padding: 10px; border-bottom: 1px solid #ecf0f1; }
+        tr:hover { background: #f8f9fa; }
+        .status-success { color: #27ae60; font-weight: bold; }
+        .status-fail { color: #e74c3c; font-weight: bold; }
+        .badge { padding: 3px 8px; border-radius: 3px; font-size: 12px; font-weight: bold; }
+        .badge-encrypted { background: #3498db; color: white; }
+        .badge-verified { background: #27ae60; color: white; }
+        .badge-tested { background: #9b59b6; color: white; }
+        .footer { margin-top: 30px; text-align: center; color: #95a5a6; font-size: 12px; }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <h1>%s</h1>
+`, title, title)
+
+	file.WriteString(htmlHeader)
+
+	// Summary section
+	totalSize := int64(0)
+	encryptedCount := 0
+	verifiedCount := 0
+	testedCount := 0
+
+	for _, entry := range entries {
+		totalSize += entry.SizeBytes
+		if entry.Encrypted {
+			encryptedCount++
+		}
+		if entry.VerifyValid != nil && *entry.VerifyValid {
+			verifiedCount++
+		}
+		if entry.DrillSuccess != nil && *entry.DrillSuccess {
+			testedCount++
+		}
+	}
+
+	var oldestBackup, newestBackup time.Time
+	if len(entries) > 0 {
+		oldestBackup = entries[0].CreatedAt
+		newestBackup = entries[len(entries)-1].CreatedAt
+	}
+
+	summaryHTML := fmt.Sprintf(`
+        <div class="summary">
+            <div class="summary-item">
+                <div class="summary-label">Total Backups:</div>
+                <div class="summary-value">%d</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">Total Size:</div>
+                <div class="summary-value">%s</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">Encrypted:</div>
+                <div class="summary-value">%d (%.1f%%)</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">Verified:</div>
+                <div class="summary-value">%d (%.1f%%)</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">DR Tested:</div>
+                <div class="summary-value">%d (%.1f%%)</div>
+            </div>
+        </div>
+        <div class="summary">
+            <div class="summary-item">
+                <div class="summary-label">Oldest Backup:</div>
+                <div class="summary-value">%s</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">Newest Backup:</div>
+                <div class="summary-value">%s</div>
+            </div>
+            <div class="summary-item">
+                <div class="summary-label">Time Span:</div>
+                <div class="summary-value">%s</div>
+            </div>
+        </div>
+`,
+		len(entries),
+		catalog.FormatSize(totalSize),
+		encryptedCount, float64(encryptedCount)/float64(len(entries))*100,
+		verifiedCount, float64(verifiedCount)/float64(len(entries))*100,
+		testedCount, float64(testedCount)/float64(len(entries))*100,
+		oldestBackup.Format("2006-01-02 15:04"),
+		newestBackup.Format("2006-01-02 15:04"),
+		formatTimeSpan(newestBackup.Sub(oldestBackup)),
+	)
+
+	file.WriteString(summaryHTML)
+
+	// Table header
+	tableHeader := `
+        <table>
+            <thead>
+                <tr>
+                    <th>Database</th>
+                    <th>Created</th>
+                    <th>Size</th>
+                    <th>Type</th>
+                    <th>Duration</th>
+                    <th>Status</th>
+                    <th>Attributes</th>
+                </tr>
+            </thead>
+            <tbody>
+`
+	file.WriteString(tableHeader)
+
+	// Table rows
+	for _, entry := range entries {
+		badges := []string{}
+		if entry.Encrypted {
+			badges = append(badges, `<span class="badge badge-encrypted">Encrypted</span>`)
+		}
+		if entry.VerifyValid != nil && *entry.VerifyValid {
+			badges = append(badges, `<span class="badge badge-verified">Verified</span>`)
+		}
+		if entry.DrillSuccess != nil && *entry.DrillSuccess {
+			badges = append(badges, `<span class="badge badge-tested">DR Tested</span>`)
+		}
+
+		statusClass := "status-success"
+		statusText := string(entry.Status)
+		if entry.Status == catalog.StatusFailed {
+			statusClass = "status-fail"
+		}
+
+		row := fmt.Sprintf(`
+                <tr>
+                    <td>%s</td>
+                    <td>%s</td>
+                    <td>%s</td>
+                    <td>%s</td>
+                    <td>%.1fs</td>
+                    <td class="%s">%s</td>
+                    <td>%s</td>
+                </tr>`,
+			html.EscapeString(entry.Database),
+			entry.CreatedAt.Format("2006-01-02 15:04:05"),
+			catalog.FormatSize(entry.SizeBytes),
+			html.EscapeString(entry.BackupType),
+			entry.Duration,
+			statusClass,
+			html.EscapeString(statusText),
+			strings.Join(badges, " "),
+		)
+		file.WriteString(row)
+	}
+
+	// Table footer and close HTML
+	htmlFooter := `
+            </tbody>
+        </table>
+        <div class="footer">
+            Generated by dbbackup on ` + time.Now().Format("2006-01-02 15:04:05") + `
+        </div>
+    </div>
+</body>
+</html>
+`
+	file.WriteString(htmlFooter)
+
+	fmt.Printf("✅ Exported %d backups to HTML: %s\n", len(entries), outputPath)
+	fmt.Printf("   Open in browser: file://%s\n", filepath.Join(os.Getenv("PWD"), exportOutput))
+	return nil
+}
+
+// exportJSON exports entries to JSON format
+func exportJSON(entries []*catalog.Entry, outputPath string) error {
+	file, err := os.Create(outputPath)
+	if err != nil {
+		return fmt.Errorf("failed to create output file: %w", err)
+	}
+	defer file.Close()
+
+	encoder := json.NewEncoder(file)
+	encoder.SetIndent("", "  ")
+
+	if err := encoder.Encode(entries); err != nil {
+		return fmt.Errorf("failed to encode JSON: %w", err)
+	}
+
+	fmt.Printf("✅ Exported %d backups to JSON: %s\n", len(entries), outputPath)
+	return nil
+}
+
+// formatTime formats *time.Time to string
+func formatTime(t *time.Time) string {
+	if t == nil {
+		return ""
+	}
+	return t.Format(time.RFC3339)
+}
+
+// formatBool formats *bool to string
+func formatBool(b *bool) string {
+	if b == nil {
+		return ""
+	}
+	if *b {
+		return "true"
+	}
+	return "false"
+}
+
+// formatExportDuration formats *time.Duration to string
+func formatExportDuration(d *time.Duration) string {
+	if d == nil {
+		return ""
+	}
+	return d.String()
+}
+
+// formatTimeSpan formats a duration in human-readable form
+func formatTimeSpan(d time.Duration) string {
+	days := int(d.Hours() / 24)
+	if days > 365 {
+		years := days / 365
+		return fmt.Sprintf("%d years", years)
+	}
+	if days > 30 {
+		months := days / 30
+		return fmt.Sprintf("%d months", months)
+	}
+	if days > 0 {
+		return fmt.Sprintf("%d days", days)
+	}
+	return fmt.Sprintf("%.0f hours", d.Hours())
+}

cmd/completion.go

@@ -0,0 +1,80 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var completionCmd = &cobra.Command{
+	Use:   "completion [bash|zsh|fish|powershell]",
+	Short: "Generate shell completion scripts",
+	Long: `Generate shell completion scripts for dbbackup commands.
+
+The completion script allows tab-completion of:
+- Commands and subcommands
+- Flags and their values
+- File paths for backup/restore operations
+
+Installation Instructions:
+
+Bash:
+  # Add to ~/.bashrc or ~/.bash_profile:
+  source <(dbbackup completion bash)
+  
+  # Or save to file and source it:
+  dbbackup completion bash > ~/.dbbackup-completion.bash
+  echo 'source ~/.dbbackup-completion.bash' >> ~/.bashrc
+
+Zsh:
+  # Add to ~/.zshrc:
+  source <(dbbackup completion zsh)
+  
+  # Or save to completion directory:
+  dbbackup completion zsh > "${fpath[1]}/_dbbackup"
+  
+  # For custom location:
+  dbbackup completion zsh > ~/.dbbackup-completion.zsh
+  echo 'source ~/.dbbackup-completion.zsh' >> ~/.zshrc
+
+Fish:
+  # Save to fish completion directory:
+  dbbackup completion fish > ~/.config/fish/completions/dbbackup.fish
+
+PowerShell:
+  # Add to your PowerShell profile:
+  dbbackup completion powershell | Out-String | Invoke-Expression
+  
+  # Or save to profile:
+  dbbackup completion powershell >> $PROFILE
+
+After installation, restart your shell or source the completion file.
+
+Note: Some flags may have conflicting shorthand letters across different
+subcommands (e.g., -d for both db-type and database). Tab completion will
+work correctly for the command you're using.`,
+	ValidArgs:          []string{"bash", "zsh", "fish", "powershell"},
+	Args:               cobra.ExactArgs(1),
+	DisableFlagParsing: true, // Don't parse flags for completion generation
+	Run: func(cmd *cobra.Command, args []string) {
+		shell := args[0]
+
+		// Get root command without triggering flag merging
+		root := cmd.Root()
+
+		switch shell {
+		case "bash":
+			root.GenBashCompletionV2(os.Stdout, true)
+		case "zsh":
+			root.GenZshCompletion(os.Stdout)
+		case "fish":
+			root.GenFishCompletion(os.Stdout, true)
+		case "powershell":
+			root.GenPowerShellCompletionWithDesc(os.Stdout)
+		}
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(completionCmd)
+}

cmd/estimate.go

@@ -0,0 +1,212 @@
+package cmd
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	"dbbackup/internal/backup"
+)
+
+var (
+	estimateDetailed bool
+	estimateJSON     bool
+)
+
+var estimateCmd = &cobra.Command{
+	Use:   "estimate",
+	Short: "Estimate backup size and duration before running",
+	Long: `Estimate how much disk space and time a backup will require.
+
+This helps plan backup operations and ensure sufficient resources are available.
+The estimation queries database statistics without performing actual backups.
+
+Examples:
+  # Estimate single database backup
+  dbbackup estimate single mydb
+
+  # Estimate full cluster backup
+  dbbackup estimate cluster
+
+  # Detailed estimation with per-database breakdown
+  dbbackup estimate cluster --detailed
+
+  # JSON output for automation
+  dbbackup estimate single mydb --json`,
+}
+
+var estimateSingleCmd = &cobra.Command{
+	Use:   "single [database]",
+	Short: "Estimate single database backup size",
+	Long: `Estimate the size and duration for backing up a single database.
+
+Provides:
+- Raw database size
+- Estimated compressed size
+- Estimated backup duration
+- Required disk space
+- Disk space availability check
+- Recommended backup profile`,
+	Args: cobra.ExactArgs(1),
+	RunE: runEstimateSingle,
+}
+
+var estimateClusterCmd = &cobra.Command{
+	Use:   "cluster",
+	Short: "Estimate full cluster backup size",
+	Long: `Estimate the size and duration for backing up an entire database cluster.
+
+Provides:
+- Total cluster size
+- Per-database breakdown (with --detailed)
+- Estimated total duration (accounting for parallelism)
+- Required disk space
+- Disk space availability check
+
+Uses configured parallelism settings to estimate actual backup time.`,
+	RunE: runEstimateCluster,
+}
+
+func init() {
+	rootCmd.AddCommand(estimateCmd)
+	estimateCmd.AddCommand(estimateSingleCmd)
+	estimateCmd.AddCommand(estimateClusterCmd)
+
+	// Flags for both subcommands
+	estimateCmd.PersistentFlags().BoolVar(&estimateDetailed, "detailed", false, "Show detailed per-database breakdown")
+	estimateCmd.PersistentFlags().BoolVar(&estimateJSON, "json", false, "Output as JSON")
+}
+
+func runEstimateSingle(cmd *cobra.Command, args []string) error {
+	ctx, cancel := context.WithTimeout(cmd.Context(), 30*time.Second)
+	defer cancel()
+
+	databaseName := args[0]
+
+	fmt.Printf("🔍 Estimating backup size for database: %s\n\n", databaseName)
+
+	estimate, err := backup.EstimateBackupSize(ctx, cfg, log, databaseName)
+	if err != nil {
+		return fmt.Errorf("estimation failed: %w", err)
+	}
+
+	if estimateJSON {
+		// Output JSON
+		fmt.Println(toJSON(estimate))
+	} else {
+		// Human-readable output
+		fmt.Println(backup.FormatSizeEstimate(estimate))
+		fmt.Printf("\n  Estimation completed in %v\n", estimate.EstimationTime)
+
+		// Warning if insufficient space
+		if !estimate.HasSufficientSpace {
+			fmt.Println()
+			fmt.Println("⚠️  WARNING: Insufficient disk space!")
+			fmt.Printf("    Need %s more space to proceed safely.\n",
+				formatBytes(estimate.RequiredDiskSpace-estimate.AvailableDiskSpace))
+			fmt.Println()
+			fmt.Println("    Recommended actions:")
+			fmt.Println("    1. Free up disk space: dbbackup cleanup /backups --retention-days 7")
+			fmt.Println("    2. Use a different backup directory: --backup-dir /other/location")
+			fmt.Println("    3. Increase disk capacity")
+		}
+	}
+
+	return nil
+}
+
+func runEstimateCluster(cmd *cobra.Command, args []string) error {
+	ctx, cancel := context.WithTimeout(cmd.Context(), 60*time.Second)
+	defer cancel()
+
+	fmt.Println("🔍 Estimating cluster backup size...")
+	fmt.Println()
+
+	estimate, err := backup.EstimateClusterBackupSize(ctx, cfg, log)
+	if err != nil {
+		return fmt.Errorf("estimation failed: %w", err)
+	}
+
+	if estimateJSON {
+		// Output JSON
+		fmt.Println(toJSON(estimate))
+	} else {
+		// Human-readable output
+		fmt.Println(backup.FormatClusterSizeEstimate(estimate))
+
+		// Detailed per-database breakdown
+		if estimateDetailed && len(estimate.DatabaseEstimates) > 0 {
+			fmt.Println()
+			fmt.Println("Per-Database Breakdown:")
+			fmt.Println("════════════════════════════════════════════════════════════")
+
+			// Sort databases by size (largest first)
+			type dbSize struct {
+				name string
+				size int64
+			}
+			var sorted []dbSize
+			for name, est := range estimate.DatabaseEstimates {
+				sorted = append(sorted, dbSize{name, est.EstimatedRawSize})
+			}
+			// Simple sort by size (descending)
+			for i := 0; i < len(sorted)-1; i++ {
+				for j := i + 1; j < len(sorted); j++ {
+					if sorted[j].size > sorted[i].size {
+						sorted[i], sorted[j] = sorted[j], sorted[i]
+					}
+				}
+			}
+
+			// Display top 10 largest
+			displayCount := len(sorted)
+			if displayCount > 10 {
+				displayCount = 10
+			}
+
+			for i := 0; i < displayCount; i++ {
+				name := sorted[i].name
+				est := estimate.DatabaseEstimates[name]
+				fmt.Printf("\n%d. %s\n", i+1, name)
+				fmt.Printf("   Raw: %s | Compressed: %s | Duration: %v\n",
+					formatBytes(est.EstimatedRawSize),
+					formatBytes(est.EstimatedCompressed),
+					est.EstimatedDuration.Round(time.Second))
+				if est.LargestTable != "" {
+					fmt.Printf("   Largest table: %s (%s)\n",
+						est.LargestTable,
+						formatBytes(est.LargestTableSize))
+				}
+			}
+
+			if len(sorted) > 10 {
+				fmt.Printf("\n... and %d more databases\n", len(sorted)-10)
+			}
+		}
+
+		// Warning if insufficient space
+		if !estimate.HasSufficientSpace {
+			fmt.Println()
+			fmt.Println("⚠️  WARNING: Insufficient disk space!")
+			fmt.Printf("    Need %s more space to proceed safely.\n",
+				formatBytes(estimate.RequiredDiskSpace-estimate.AvailableDiskSpace))
+			fmt.Println()
+			fmt.Println("    Recommended actions:")
+			fmt.Println("    1. Free up disk space: dbbackup cleanup /backups --retention-days 7")
+			fmt.Println("    2. Use a different backup directory: --backup-dir /other/location")
+			fmt.Println("    3. Increase disk capacity")
+			fmt.Println("    4. Back up databases individually to spread across time/space")
+		}
+	}
+
+	return nil
+}
+
+// toJSON converts any struct to JSON string (simple helper)
+func toJSON(v interface{}) string {
+	b, _ := json.Marshal(v)
+	return string(b)
+}

cmd/man.go

@@ -0,0 +1,182 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/cobra/doc"
+)
+
+var (
+	manOutputDir string
+)
+
+var manCmd = &cobra.Command{
+	Use:   "man",
+	Short: "Generate man pages for dbbackup",
+	Long: `Generate Unix manual (man) pages for all dbbackup commands.
+
+Man pages are generated in standard groff format and can be viewed
+with the 'man' command or installed system-wide.
+
+Installation:
+  # Generate pages
+  dbbackup man --output /tmp/man
+
+  # Install system-wide (requires root)
+  sudo cp /tmp/man/*.1 /usr/local/share/man/man1/
+  sudo mandb  # Update man database
+
+  # View pages
+  man dbbackup
+  man dbbackup-backup
+  man dbbackup-restore
+
+Examples:
+  # Generate to current directory
+  dbbackup man
+
+  # Generate to specific directory
+  dbbackup man --output ./docs/man
+
+  # Generate and install system-wide
+  dbbackup man --output /tmp/man && \
+    sudo cp /tmp/man/*.1 /usr/local/share/man/man1/ && \
+    sudo mandb`,
+	DisableFlagParsing: true, // Avoid shorthand conflicts during generation
+	RunE:               runGenerateMan,
+}
+
+func init() {
+	rootCmd.AddCommand(manCmd)
+	manCmd.Flags().StringVarP(&manOutputDir, "output", "o", "./man", "Output directory for man pages")
+
+	// Parse flags manually since DisableFlagParsing is enabled
+	manCmd.SetHelpFunc(func(cmd *cobra.Command, args []string) {
+		cmd.Parent().HelpFunc()(cmd, args)
+	})
+}
+
+func runGenerateMan(cmd *cobra.Command, args []string) error {
+	// Parse flags manually since DisableFlagParsing is enabled
+	outputDir := "./man"
+	for i := 0; i < len(args); i++ {
+		if args[i] == "--output" || args[i] == "-o" {
+			if i+1 < len(args) {
+				outputDir = args[i+1]
+				i++
+			}
+		}
+	}
+
+	// Create output directory
+	if err := os.MkdirAll(outputDir, 0755); err != nil {
+		return fmt.Errorf("failed to create output directory: %w", err)
+	}
+
+	// Generate man pages for root and all subcommands
+	header := &doc.GenManHeader{
+		Title:   "DBBACKUP",
+		Section: "1",
+		Source:  "dbbackup",
+		Manual:  "Database Backup Tool",
+	}
+
+	// Due to shorthand flag conflicts in some subcommands (-d for db-type vs database),
+	// we generate man pages command-by-command, catching any errors
+	root := cmd.Root()
+	generatedCount := 0
+	failedCount := 0
+
+	// Helper to generate man page for a single command
+	genManForCommand := func(c *cobra.Command) {
+		// Recover from panic due to flag conflicts
+		defer func() {
+			if r := recover(); r != nil {
+				failedCount++
+				// Silently skip commands with flag conflicts
+			}
+		}()
+
+		filename := filepath.Join(outputDir, c.CommandPath()+".1")
+		// Replace spaces with hyphens for filename
+		filename = filepath.Join(outputDir, filepath.Base(c.CommandPath())+".1")
+
+		f, err := os.Create(filename)
+		if err != nil {
+			failedCount++
+			return
+		}
+		defer f.Close()
+
+		if err := doc.GenMan(c, header, f); err != nil {
+			failedCount++
+			os.Remove(filename) // Clean up partial file
+		} else {
+			generatedCount++
+		}
+	}
+
+	// Generate for root command
+	genManForCommand(root)
+
+	// Walk through all commands
+	var walkCommands func(*cobra.Command)
+	walkCommands = func(c *cobra.Command) {
+		for _, sub := range c.Commands() {
+			// Skip hidden commands
+			if sub.Hidden {
+				continue
+			}
+
+			// Try to generate man page
+			genManForCommand(sub)
+
+			// Recurse into subcommands
+			walkCommands(sub)
+		}
+	}
+
+	walkCommands(root)
+
+	fmt.Printf("✅ Generated %d man pages in %s", generatedCount, outputDir)
+	if failedCount > 0 {
+		fmt.Printf(" (%d skipped due to flag conflicts)\n", failedCount)
+	} else {
+		fmt.Println()
+	}
+	fmt.Println()
+
+	fmt.Println("📖 Installation Instructions:")
+	fmt.Println()
+	fmt.Println("  1. Install system-wide (requires root):")
+	fmt.Printf("     sudo cp %s/*.1 /usr/local/share/man/man1/\n", outputDir)
+	fmt.Println("     sudo mandb")
+	fmt.Println()
+	fmt.Println("  2. Test locally (no installation):")
+	fmt.Printf("     man -l %s/dbbackup.1\n", outputDir)
+	fmt.Println()
+	fmt.Println("  3. View installed pages:")
+	fmt.Println("     man dbbackup")
+	fmt.Println("     man dbbackup-backup")
+	fmt.Println("     man dbbackup-restore")
+	fmt.Println()
+
+	// Show some example pages
+	files, err := filepath.Glob(filepath.Join(outputDir, "*.1"))
+	if err == nil && len(files) > 0 {
+		fmt.Println("📋 Generated Pages (sample):")
+		for i, file := range files {
+			if i >= 5 {
+				fmt.Printf("   ... and %d more\n", len(files)-5)
+				break
+			}
+			fmt.Printf("   - %s\n", filepath.Base(file))
+		}
+		fmt.Println()
+	}
+
+	return nil
+}

cmd/version.go

@@ -0,0 +1,168 @@
+// Package cmd - version command showing detailed build and system info
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+
+	"github.com/spf13/cobra"
+)
+
+var versionOutputFormat string
+
+var versionCmd = &cobra.Command{
+	Use:   "version",
+	Short: "Show detailed version and system information",
+	Long: `Display comprehensive version information including:
+
+  - dbbackup version, build time, and git commit
+  - Go runtime version
+  - Operating system and architecture
+  - Installed database tool versions (pg_dump, mysqldump, etc.)
+  - System information
+
+Useful for troubleshooting and bug reports.
+
+Examples:
+  # Show version info
+  dbbackup version
+
+  # JSON output for scripts
+  dbbackup version --format json
+
+  # Short version only
+  dbbackup version --format short`,
+	Run: runVersionCmd,
+}
+
+func init() {
+	rootCmd.AddCommand(versionCmd)
+	versionCmd.Flags().StringVar(&versionOutputFormat, "format", "table", "Output format (table, json, short)")
+}
+
+type versionInfo struct {
+	Version     string            `json:"version"`
+	BuildTime   string            `json:"build_time"`
+	GitCommit   string            `json:"git_commit"`
+	GoVersion   string            `json:"go_version"`
+	OS          string            `json:"os"`
+	Arch        string            `json:"arch"`
+	NumCPU      int               `json:"num_cpu"`
+	DatabaseTools map[string]string `json:"database_tools"`
+}
+
+func runVersionCmd(cmd *cobra.Command, args []string) {
+	info := collectVersionInfo()
+	
+	switch versionOutputFormat {
+	case "json":
+		outputVersionJSON(info)
+	case "short":
+		fmt.Printf("dbbackup %s\n", info.Version)
+	default:
+		outputTable(info)
+	}
+}
+
+func collectVersionInfo() versionInfo {
+	info := versionInfo{
+		Version:       cfg.Version,
+		BuildTime:     cfg.BuildTime,
+		GitCommit:     cfg.GitCommit,
+		GoVersion:     runtime.Version(),
+		OS:            runtime.GOOS,
+		Arch:          runtime.GOARCH,
+		NumCPU:        runtime.NumCPU(),
+		DatabaseTools: make(map[string]string),
+	}
+	
+	// Check database tools
+	tools := []struct {
+		name    string
+		command string
+		args    []string
+	}{
+		{"pg_dump", "pg_dump", []string{"--version"}},
+		{"pg_restore", "pg_restore", []string{"--version"}},
+		{"psql", "psql", []string{"--version"}},
+		{"mysqldump", "mysqldump", []string{"--version"}},
+		{"mysql", "mysql", []string{"--version"}},
+		{"mariadb-dump", "mariadb-dump", []string{"--version"}},
+	}
+	
+	for _, tool := range tools {
+		version := getToolVersion(tool.command, tool.args)
+		if version != "" {
+			info.DatabaseTools[tool.name] = version
+		}
+	}
+	
+	return info
+}
+
+func getToolVersion(command string, args []string) string {
+	cmd := exec.Command(command, args...)
+	output, err := cmd.Output()
+	if err != nil {
+		return ""
+	}
+	
+	// Parse first line and extract version
+	line := strings.Split(string(output), "\n")[0]
+	line = strings.TrimSpace(line)
+	
+	// Try to extract just the version number
+	// e.g., "pg_dump (PostgreSQL) 16.1" -> "16.1"
+	// e.g., "mysqldump  Ver 8.0.35" -> "8.0.35"
+	parts := strings.Fields(line)
+	if len(parts) > 0 {
+		// Return last part which is usually the version
+		return parts[len(parts)-1]
+	}
+	
+	return line
+}
+
+func outputVersionJSON(info versionInfo) {
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
+	enc.Encode(info)
+}
+
+func outputTable(info versionInfo) {
+	fmt.Println()
+	fmt.Println("╔═══════════════════════════════════════════════════════════════╗")
+	fmt.Println("║                    dbbackup Version Info                       ║")
+	fmt.Println("╠═══════════════════════════════════════════════════════════════╣")
+	fmt.Printf("║  %-20s %-40s ║\n", "Version:", info.Version)
+	fmt.Printf("║  %-20s %-40s ║\n", "Build Time:", info.BuildTime)
+	
+	// Truncate commit if too long
+	commit := info.GitCommit
+	if len(commit) > 40 {
+		commit = commit[:40]
+	}
+	fmt.Printf("║  %-20s %-40s ║\n", "Git Commit:", commit)
+	fmt.Println("╠═══════════════════════════════════════════════════════════════╣")
+	fmt.Printf("║  %-20s %-40s ║\n", "Go Version:", info.GoVersion)
+	fmt.Printf("║  %-20s %-40s ║\n", "OS/Arch:", fmt.Sprintf("%s/%s", info.OS, info.Arch))
+	fmt.Printf("║  %-20s %-40d ║\n", "CPU Cores:", info.NumCPU)
+	fmt.Println("╠═══════════════════════════════════════════════════════════════╣")
+	fmt.Println("║  Database Tools                                                ║")
+	fmt.Println("╟───────────────────────────────────────────────────────────────╢")
+	
+	if len(info.DatabaseTools) == 0 {
+		fmt.Println("║    (none detected)                                            ║")
+	} else {
+		for tool, version := range info.DatabaseTools {
+			fmt.Printf("║    %-18s %-41s ║\n", tool+":", version)
+		}
+	}
+	
+	fmt.Println("╚═══════════════════════════════════════════════════════════════╝")
+	fmt.Println()
+}

go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/hashicorp/go-multierror v1.1.1
 	github.com/jackc/pgx/v5 v5.7.6
 	github.com/klauspost/pgzip v1.2.6
+	github.com/mattn/go-isatty v0.0.20
 	github.com/schollz/progressbar/v3 v3.19.0
 	github.com/shirou/gopsutil/v3 v3.24.5
 	github.com/sirupsen/logrus v1.9.3
@@ -69,6 +70,7 @@ require (
 	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
 	github.com/charmbracelet/x/term v0.2.1 // indirect
 	github.com/cncf/xds/go v0.0.0-20250501225837-2ac532fd4443 // indirect
+	github.com/cpuguy83/go-md2man/v2 v2.0.6 // indirect
 	github.com/envoyproxy/go-control-plane/envoy v1.32.4 // indirect
 	github.com/envoyproxy/protoc-gen-validate v1.2.1 // indirect
 	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
@@ -90,7 +92,6 @@ require (
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
-	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-localereader v0.0.1 // indirect
 	github.com/mattn/go-runewidth v0.0.16 // indirect
 	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db // indirect
@@ -102,6 +103,7 @@ require (
 	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.5.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect
 	github.com/tklauser/numcpus v0.6.1 // indirect
@@ -130,6 +132,7 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251103181224-f26f9409b101 // indirect
 	google.golang.org/grpc v1.76.0 // indirect
 	google.golang.org/protobuf v1.36.10 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 	modernc.org/libc v1.67.6 // indirect
 	modernc.org/mathutil v1.7.1 // indirect
 	modernc.org/memory v1.11.0 // indirect

go.sum

@@ -106,6 +106,7 @@ github.com/chengxilo/virtualterm v1.0.4 h1:Z6IpERbRVlfB8WkOmtbHiDbBANU7cimRIof7m
 github.com/chengxilo/virtualterm v1.0.4/go.mod h1:DyxxBZz/x1iqJjFxTFcr6/x+jSpqN0iwWCOK1q10rlY=
 github.com/cncf/xds/go v0.0.0-20250501225837-2ac532fd4443 h1:aQ3y1lwWyqYPiWZThqv1aFbZMiM9vblcSArJRf2Irls=
 github.com/cncf/xds/go v0.0.0-20250501225837-2ac532fd4443/go.mod h1:W+zGtBO5Y1IgJhy4+A9GOqVhqLpfZi+vwmdNXUehLA8=
+github.com/cpuguy83/go-md2man/v2 v2.0.6 h1:XJtiaUW6dEEqVuZiMTn1ldk455QWwEIsMIJlo5vtkx0=
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -177,6 +178,10 @@ github.com/klauspost/compress v1.18.3 h1:9PJRvfbmTabkOX8moIpXPbMMbYN60bWImDDU7L+
 github.com/klauspost/compress v1.18.3/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
 github.com/klauspost/pgzip v1.2.6 h1:8RXeL5crjEUFnR2/Sn6GJNWtSQ3Dk8pq4CL3jvdDyjU=
 github.com/klauspost/pgzip v1.2.6/go.mod h1:Ch1tH69qFZu15pkjo5kYi6mth2Zzwzt50oCQKQE9RUs=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
@@ -216,6 +221,9 @@ github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec/go.mod h1:qq
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
 github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR38lUII=
+github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
+github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/schollz/progressbar/v3 v3.19.0 h1:Ea18xuIRQXLAUidVDox3AbwfUhD0/1IvohyTutOIFoc=
 github.com/schollz/progressbar/v3 v3.19.0/go.mod h1:IsO3lpbaGuzh8zIMzgY3+J8l4C8GjO0Y9S69eFvNsec=
@@ -312,6 +320,8 @@ google.golang.org/grpc v1.76.0/go.mod h1:Ju12QI8M6iQJtbcsV+awF5a4hfJMLi4X0JLo94U
 google.golang.org/protobuf v1.36.10 h1:AYd7cD/uASjIL6Q9LiTjz8JLcrh/88q5UObnmY3aOOE=
 google.golang.org/protobuf v1.36.10/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/backup/estimate.go

@@ -0,0 +1,315 @@
+package backup
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+
+	"github.com/shirou/gopsutil/v3/disk"
+
+	"dbbackup/internal/config"
+	"dbbackup/internal/database"
+	"dbbackup/internal/logger"
+)
+
+// SizeEstimate contains backup size estimation results
+type SizeEstimate struct {
+	DatabaseName        string        `json:"database_name"`
+	EstimatedRawSize    int64         `json:"estimated_raw_size_bytes"`
+	EstimatedCompressed int64         `json:"estimated_compressed_bytes"`
+	CompressionRatio    float64       `json:"compression_ratio"`
+	TableCount          int           `json:"table_count"`
+	LargestTable        string        `json:"largest_table,omitempty"`
+	LargestTableSize    int64         `json:"largest_table_size_bytes,omitempty"`
+	EstimatedDuration   time.Duration `json:"estimated_duration"`
+	RecommendedProfile  string        `json:"recommended_profile"`
+	RequiredDiskSpace   int64         `json:"required_disk_space_bytes"`
+	AvailableDiskSpace  int64         `json:"available_disk_space_bytes"`
+	HasSufficientSpace  bool          `json:"has_sufficient_space"`
+	EstimationTime      time.Duration `json:"estimation_time"`
+}
+
+// ClusterSizeEstimate contains cluster-wide size estimation
+type ClusterSizeEstimate struct {
+	TotalDatabases      int                      `json:"total_databases"`
+	TotalRawSize        int64                    `json:"total_raw_size_bytes"`
+	TotalCompressed     int64                    `json:"total_compressed_bytes"`
+	LargestDatabase     string                   `json:"largest_database,omitempty"`
+	LargestDatabaseSize int64                    `json:"largest_database_size_bytes,omitempty"`
+	EstimatedDuration   time.Duration            `json:"estimated_duration"`
+	RequiredDiskSpace   int64                    `json:"required_disk_space_bytes"`
+	AvailableDiskSpace  int64                    `json:"available_disk_space_bytes"`
+	HasSufficientSpace  bool                     `json:"has_sufficient_space"`
+	DatabaseEstimates   map[string]*SizeEstimate `json:"database_estimates,omitempty"`
+	EstimationTime      time.Duration            `json:"estimation_time"`
+}
+
+// EstimateBackupSize estimates the size of a single database backup
+func EstimateBackupSize(ctx context.Context, cfg *config.Config, log logger.Logger, databaseName string) (*SizeEstimate, error) {
+	startTime := time.Now()
+
+	estimate := &SizeEstimate{
+		DatabaseName: databaseName,
+	}
+
+	// Create database connection
+	db, err := database.New(cfg, log)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create database instance: %w", err)
+	}
+	defer db.Close()
+
+	if err := db.Connect(ctx); err != nil {
+		return nil, fmt.Errorf("failed to connect to database: %w", err)
+	}
+
+	// Get database size based on engine type
+	rawSize, err := db.GetDatabaseSize(ctx, databaseName)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get database size: %w", err)
+	}
+	estimate.EstimatedRawSize = rawSize
+
+	// Get table statistics
+	tables, err := db.ListTables(ctx, databaseName)
+	if err == nil {
+		estimate.TableCount = len(tables)
+	}
+
+	// For PostgreSQL and MySQL, get additional detailed statistics
+	if cfg.IsPostgreSQL() {
+		pg := db.(*database.PostgreSQL)
+		if err := estimatePostgresSize(ctx, pg.GetConn(), databaseName, estimate); err != nil {
+			log.Debug("Could not get detailed PostgreSQL stats: %v", err)
+		}
+	} else if cfg.IsMySQL() {
+		my := db.(*database.MySQL)
+		if err := estimateMySQLSize(ctx, my.GetConn(), databaseName, estimate); err != nil {
+			log.Debug("Could not get detailed MySQL stats: %v", err)
+		}
+	}
+
+	// Calculate compression ratio (typical: 70-80% for databases)
+	estimate.CompressionRatio = 0.25 // Assume 75% compression (1/4 of original size)
+	if cfg.CompressionLevel >= 6 {
+		estimate.CompressionRatio = 0.20 // Better compression with higher levels
+	}
+	estimate.EstimatedCompressed = int64(float64(estimate.EstimatedRawSize) * estimate.CompressionRatio)
+
+	// Estimate duration (rough: 50 MB/s for pg_dump, 100 MB/s for mysqldump)
+	throughputMBps := 50.0
+	if cfg.IsMySQL() {
+		throughputMBps = 100.0
+	}
+
+	sizeGB := float64(estimate.EstimatedRawSize) / (1024 * 1024 * 1024)
+	durationMinutes := (sizeGB * 1024) / throughputMBps / 60
+	estimate.EstimatedDuration = time.Duration(durationMinutes * float64(time.Minute))
+
+	// Recommend profile based on size
+	if sizeGB < 1 {
+		estimate.RecommendedProfile = "balanced"
+	} else if sizeGB < 10 {
+		estimate.RecommendedProfile = "performance"
+	} else if sizeGB < 100 {
+		estimate.RecommendedProfile = "turbo"
+	} else {
+		estimate.RecommendedProfile = "conservative" // Large DB, be careful
+	}
+
+	// Calculate required disk space (3x compressed size for safety: temp + compressed + checksum)
+	estimate.RequiredDiskSpace = estimate.EstimatedCompressed * 3
+
+	// Check available disk space
+	if cfg.BackupDir != "" {
+		if usage, err := disk.Usage(cfg.BackupDir); err == nil {
+			estimate.AvailableDiskSpace = int64(usage.Free)
+			estimate.HasSufficientSpace = estimate.AvailableDiskSpace > estimate.RequiredDiskSpace
+		}
+	}
+
+	estimate.EstimationTime = time.Since(startTime)
+	return estimate, nil
+}
+
+// EstimateClusterBackupSize estimates the size of a full cluster backup
+func EstimateClusterBackupSize(ctx context.Context, cfg *config.Config, log logger.Logger) (*ClusterSizeEstimate, error) {
+	startTime := time.Now()
+
+	estimate := &ClusterSizeEstimate{
+		DatabaseEstimates: make(map[string]*SizeEstimate),
+	}
+
+	// Create database connection
+	db, err := database.New(cfg, log)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create database instance: %w", err)
+	}
+	defer db.Close()
+
+	if err := db.Connect(ctx); err != nil {
+		return nil, fmt.Errorf("failed to connect to database: %w", err)
+	}
+
+	// List all databases
+	databases, err := db.ListDatabases(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list databases: %w", err)
+	}
+
+	estimate.TotalDatabases = len(databases)
+
+	// Estimate each database
+	for _, dbName := range databases {
+		dbEstimate, err := EstimateBackupSize(ctx, cfg, log, dbName)
+		if err != nil {
+			log.Warn("Failed to estimate database size", "database", dbName, "error", err)
+			continue
+		}
+
+		estimate.DatabaseEstimates[dbName] = dbEstimate
+		estimate.TotalRawSize += dbEstimate.EstimatedRawSize
+		estimate.TotalCompressed += dbEstimate.EstimatedCompressed
+
+		// Track largest database
+		if dbEstimate.EstimatedRawSize > estimate.LargestDatabaseSize {
+			estimate.LargestDatabase = dbName
+			estimate.LargestDatabaseSize = dbEstimate.EstimatedRawSize
+		}
+	}
+
+	// Estimate total duration (assume some parallelism)
+	parallelism := float64(cfg.Jobs)
+	if parallelism < 1 {
+		parallelism = 1
+	}
+
+	// Calculate serial duration first
+	var serialDuration time.Duration
+	for _, dbEst := range estimate.DatabaseEstimates {
+		serialDuration += dbEst.EstimatedDuration
+	}
+
+	// Adjust for parallelism (not perfect but reasonable)
+	estimate.EstimatedDuration = time.Duration(float64(serialDuration) / parallelism)
+
+	// Calculate required disk space
+	estimate.RequiredDiskSpace = estimate.TotalCompressed * 3
+
+	// Check available disk space
+	if cfg.BackupDir != "" {
+		if usage, err := disk.Usage(cfg.BackupDir); err == nil {
+			estimate.AvailableDiskSpace = int64(usage.Free)
+			estimate.HasSufficientSpace = estimate.AvailableDiskSpace > estimate.RequiredDiskSpace
+		}
+	}
+
+	estimate.EstimationTime = time.Since(startTime)
+	return estimate, nil
+}
+
+// estimatePostgresSize gets detailed statistics from PostgreSQL
+func estimatePostgresSize(ctx context.Context, conn *sql.DB, databaseName string, estimate *SizeEstimate) error {
+	// Note: EstimatedRawSize and TableCount are already set by interface methods
+
+	// Get largest table size
+	largestQuery := `
+		SELECT 
+			schemaname || '.' || tablename as table_name,
+			pg_total_relation_size(schemaname||'.'||tablename) as size_bytes
+		FROM pg_tables
+		WHERE schemaname NOT IN ('pg_catalog', 'information_schema')
+		ORDER BY pg_total_relation_size(schemaname||'.'||tablename) DESC
+		LIMIT 1
+	`
+	var tableName string
+	var tableSize int64
+	if err := conn.QueryRowContext(ctx, largestQuery).Scan(&tableName, &tableSize); err == nil {
+		estimate.LargestTable = tableName
+		estimate.LargestTableSize = tableSize
+	}
+
+	return nil
+}
+
+// estimateMySQLSize gets detailed statistics from MySQL/MariaDB
+func estimateMySQLSize(ctx context.Context, conn *sql.DB, databaseName string, estimate *SizeEstimate) error {
+	// Note: EstimatedRawSize and TableCount are already set by interface methods
+
+	// Get largest table
+	largestQuery := `
+		SELECT 
+			table_name,
+			data_length + index_length as size_bytes
+		FROM information_schema.TABLES
+		WHERE table_schema = ?
+		ORDER BY (data_length + index_length) DESC
+		LIMIT 1
+	`
+	var tableName string
+	var tableSize int64
+	if err := conn.QueryRowContext(ctx, largestQuery, databaseName).Scan(&tableName, &tableSize); err == nil {
+		estimate.LargestTable = tableName
+		estimate.LargestTableSize = tableSize
+	}
+
+	return nil
+}
+
+// FormatSizeEstimate returns a human-readable summary
+func FormatSizeEstimate(estimate *SizeEstimate) string {
+	return fmt.Sprintf(`Database: %s
+  Raw Size:           %s
+  Compressed Size:    %s (%.0f%% compression)
+  Tables:             %d
+  Largest Table:      %s (%s)
+  Estimated Duration: %s
+  Recommended Profile: %s
+  Required Disk Space: %s
+  Available Space:    %s
+  Status:             %s`,
+		estimate.DatabaseName,
+		formatBytes(estimate.EstimatedRawSize),
+		formatBytes(estimate.EstimatedCompressed),
+		(1.0-estimate.CompressionRatio)*100,
+		estimate.TableCount,
+		estimate.LargestTable,
+		formatBytes(estimate.LargestTableSize),
+		estimate.EstimatedDuration.Round(time.Second),
+		estimate.RecommendedProfile,
+		formatBytes(estimate.RequiredDiskSpace),
+		formatBytes(estimate.AvailableDiskSpace),
+		getSpaceStatus(estimate.HasSufficientSpace))
+}
+
+// FormatClusterSizeEstimate returns a human-readable summary
+func FormatClusterSizeEstimate(estimate *ClusterSizeEstimate) string {
+	return fmt.Sprintf(`Cluster Backup Estimate:
+  Total Databases:    %d
+  Total Raw Size:     %s
+  Total Compressed:   %s
+  Largest Database:   %s (%s)
+  Estimated Duration: %s
+  Required Disk Space: %s
+  Available Space:    %s
+  Status:             %s
+  Estimation Time:    %v`,
+		estimate.TotalDatabases,
+		formatBytes(estimate.TotalRawSize),
+		formatBytes(estimate.TotalCompressed),
+		estimate.LargestDatabase,
+		formatBytes(estimate.LargestDatabaseSize),
+		estimate.EstimatedDuration.Round(time.Second),
+		formatBytes(estimate.RequiredDiskSpace),
+		formatBytes(estimate.AvailableDiskSpace),
+		getSpaceStatus(estimate.HasSufficientSpace),
+		estimate.EstimationTime)
+}
+
+func getSpaceStatus(hasSufficient bool) string {
+	if hasSufficient {
+		return "✅ Sufficient"
+	}
+	return "⚠️  INSUFFICIENT - Free up space first!"
+}

internal/checks/diagnostics.go

@@ -0,0 +1,386 @@
+package checks
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/shirou/gopsutil/v3/disk"
+	"github.com/shirou/gopsutil/v3/mem"
+)
+
+// ErrorContext provides environmental context for debugging errors
+type ErrorContext struct {
+	// System info
+	AvailableDiskSpace  uint64  `json:"available_disk_space"`
+	TotalDiskSpace      uint64  `json:"total_disk_space"`
+	DiskUsagePercent    float64 `json:"disk_usage_percent"`
+	AvailableMemory     uint64  `json:"available_memory"`
+	TotalMemory         uint64  `json:"total_memory"`
+	MemoryUsagePercent  float64 `json:"memory_usage_percent"`
+	OpenFileDescriptors uint64  `json:"open_file_descriptors,omitempty"`
+	MaxFileDescriptors  uint64  `json:"max_file_descriptors,omitempty"`
+
+	// Database info (if connection available)
+	DatabaseVersion    string `json:"database_version,omitempty"`
+	MaxConnections     int    `json:"max_connections,omitempty"`
+	CurrentConnections int    `json:"current_connections,omitempty"`
+	MaxLocksPerTxn     int    `json:"max_locks_per_transaction,omitempty"`
+	SharedMemory       string `json:"shared_memory,omitempty"`
+
+	// Network info
+	CanReachDatabase bool   `json:"can_reach_database"`
+	DatabaseHost     string `json:"database_host,omitempty"`
+	DatabasePort     int    `json:"database_port,omitempty"`
+
+	// Timing
+	CollectedAt time.Time `json:"collected_at"`
+}
+
+// DiagnosticsReport combines error classification with environmental context
+type DiagnosticsReport struct {
+	Classification  *ErrorClassification `json:"classification"`
+	Context         *ErrorContext        `json:"context"`
+	Recommendations []string             `json:"recommendations"`
+	RootCause       string               `json:"root_cause,omitempty"`
+}
+
+// GatherErrorContext collects environmental information for error diagnosis
+func GatherErrorContext(backupDir string, db *sql.DB) *ErrorContext {
+	ctx := &ErrorContext{
+		CollectedAt: time.Now(),
+	}
+
+	// Gather disk space information
+	if backupDir != "" {
+		usage, err := disk.Usage(backupDir)
+		if err == nil {
+			ctx.AvailableDiskSpace = usage.Free
+			ctx.TotalDiskSpace = usage.Total
+			ctx.DiskUsagePercent = usage.UsedPercent
+		}
+	}
+
+	// Gather memory information
+	vmStat, err := mem.VirtualMemory()
+	if err == nil {
+		ctx.AvailableMemory = vmStat.Available
+		ctx.TotalMemory = vmStat.Total
+		ctx.MemoryUsagePercent = vmStat.UsedPercent
+	}
+
+	// Gather file descriptor limits (Linux/Unix only)
+	if runtime.GOOS != "windows" {
+		var rLimit syscall.Rlimit
+		if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit); err == nil {
+			ctx.MaxFileDescriptors = rLimit.Cur
+			// Try to get current open FDs (this is platform-specific)
+			if fds, err := countOpenFileDescriptors(); err == nil {
+				ctx.OpenFileDescriptors = fds
+			}
+		}
+	}
+
+	// Gather database-specific context (if connection available)
+	if db != nil {
+		gatherDatabaseContext(db, ctx)
+	}
+
+	return ctx
+}
+
+// countOpenFileDescriptors counts currently open file descriptors (Linux only)
+func countOpenFileDescriptors() (uint64, error) {
+	if runtime.GOOS != "linux" {
+		return 0, fmt.Errorf("not supported on %s", runtime.GOOS)
+	}
+
+	pid := os.Getpid()
+	fdDir := fmt.Sprintf("/proc/%d/fd", pid)
+	entries, err := os.ReadDir(fdDir)
+	if err != nil {
+		return 0, err
+	}
+	return uint64(len(entries)), nil
+}
+
+// gatherDatabaseContext collects PostgreSQL-specific diagnostics
+func gatherDatabaseContext(db *sql.DB, ctx *ErrorContext) {
+	// Set timeout for diagnostic queries
+	diagCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	// Get PostgreSQL version
+	var version string
+	if err := db.QueryRowContext(diagCtx, "SELECT version()").Scan(&version); err == nil {
+		// Extract short version (e.g., "PostgreSQL 14.5")
+		parts := strings.Fields(version)
+		if len(parts) >= 2 {
+			ctx.DatabaseVersion = parts[0] + " " + parts[1]
+		}
+	}
+
+	// Get max_connections
+	var maxConns int
+	if err := db.QueryRowContext(diagCtx, "SHOW max_connections").Scan(&maxConns); err == nil {
+		ctx.MaxConnections = maxConns
+	}
+
+	// Get current connections
+	var currConns int
+	query := "SELECT count(*) FROM pg_stat_activity"
+	if err := db.QueryRowContext(diagCtx, query).Scan(&currConns); err == nil {
+		ctx.CurrentConnections = currConns
+	}
+
+	// Get max_locks_per_transaction
+	var maxLocks int
+	if err := db.QueryRowContext(diagCtx, "SHOW max_locks_per_transaction").Scan(&maxLocks); err == nil {
+		ctx.MaxLocksPerTxn = maxLocks
+	}
+
+	// Get shared_buffers
+	var sharedBuffers string
+	if err := db.QueryRowContext(diagCtx, "SHOW shared_buffers").Scan(&sharedBuffers); err == nil {
+		ctx.SharedMemory = sharedBuffers
+	}
+}
+
+// DiagnoseError analyzes an error with full environmental context
+func DiagnoseError(errorMsg string, backupDir string, db *sql.DB) *DiagnosticsReport {
+	classification := ClassifyError(errorMsg)
+	context := GatherErrorContext(backupDir, db)
+
+	report := &DiagnosticsReport{
+		Classification:  classification,
+		Context:         context,
+		Recommendations: make([]string, 0),
+	}
+
+	// Generate context-specific recommendations
+	generateContextualRecommendations(report)
+
+	// Try to determine root cause
+	report.RootCause = analyzeRootCause(report)
+
+	return report
+}
+
+// generateContextualRecommendations creates recommendations based on error + environment
+func generateContextualRecommendations(report *DiagnosticsReport) {
+	ctx := report.Context
+	classification := report.Classification
+
+	// Disk space recommendations
+	if classification.Category == "disk_space" || ctx.DiskUsagePercent > 90 {
+		report.Recommendations = append(report.Recommendations,
+			fmt.Sprintf("⚠ Disk is %.1f%% full (%s available)",
+				ctx.DiskUsagePercent, formatBytes(ctx.AvailableDiskSpace)))
+		report.Recommendations = append(report.Recommendations,
+			"• Clean up old backups: find /mnt/backups -type f -mtime +30 -delete")
+		report.Recommendations = append(report.Recommendations,
+			"• Enable automatic cleanup: dbbackup cleanup --retention-days 30")
+	}
+
+	// Memory recommendations
+	if ctx.MemoryUsagePercent > 85 {
+		report.Recommendations = append(report.Recommendations,
+			fmt.Sprintf("⚠ Memory is %.1f%% full (%s available)",
+				ctx.MemoryUsagePercent, formatBytes(ctx.AvailableMemory)))
+		report.Recommendations = append(report.Recommendations,
+			"• Consider reducing parallel jobs: --jobs 2")
+		report.Recommendations = append(report.Recommendations,
+			"• Use conservative restore profile: dbbackup restore --profile conservative")
+	}
+
+	// File descriptor recommendations
+	if ctx.OpenFileDescriptors > 0 && ctx.MaxFileDescriptors > 0 {
+		fdUsagePercent := float64(ctx.OpenFileDescriptors) / float64(ctx.MaxFileDescriptors) * 100
+		if fdUsagePercent > 80 {
+			report.Recommendations = append(report.Recommendations,
+				fmt.Sprintf("⚠ File descriptors at %.0f%% (%d/%d used)",
+					fdUsagePercent, ctx.OpenFileDescriptors, ctx.MaxFileDescriptors))
+			report.Recommendations = append(report.Recommendations,
+				"• Increase limit: ulimit -n 8192")
+			report.Recommendations = append(report.Recommendations,
+				"• Or add to /etc/security/limits.conf: dbbackup soft nofile 8192")
+		}
+	}
+
+	// PostgreSQL lock recommendations
+	if classification.Category == "locks" && ctx.MaxLocksPerTxn > 0 {
+		totalLocks := ctx.MaxLocksPerTxn * (ctx.MaxConnections + 100)
+		report.Recommendations = append(report.Recommendations,
+			fmt.Sprintf("Current lock capacity: %d locks (max_locks_per_transaction × max_connections)",
+				totalLocks))
+
+		if ctx.MaxLocksPerTxn < 2048 {
+			report.Recommendations = append(report.Recommendations,
+				fmt.Sprintf("⚠ max_locks_per_transaction is low (%d)", ctx.MaxLocksPerTxn))
+			report.Recommendations = append(report.Recommendations,
+				"• Increase: ALTER SYSTEM SET max_locks_per_transaction = 4096;")
+			report.Recommendations = append(report.Recommendations,
+				"• Then restart PostgreSQL: sudo systemctl restart postgresql")
+		}
+
+		if ctx.MaxConnections < 20 {
+			report.Recommendations = append(report.Recommendations,
+				fmt.Sprintf("⚠ Low max_connections (%d) reduces total lock capacity", ctx.MaxConnections))
+			report.Recommendations = append(report.Recommendations,
+				"• With fewer connections, you need HIGHER max_locks_per_transaction")
+		}
+	}
+
+	// Connection recommendations
+	if classification.Category == "network" && ctx.CurrentConnections > 0 {
+		connUsagePercent := float64(ctx.CurrentConnections) / float64(ctx.MaxConnections) * 100
+		if connUsagePercent > 80 {
+			report.Recommendations = append(report.Recommendations,
+				fmt.Sprintf("⚠ Connection pool at %.0f%% capacity (%d/%d used)",
+					connUsagePercent, ctx.CurrentConnections, ctx.MaxConnections))
+			report.Recommendations = append(report.Recommendations,
+				"• Close idle connections or increase max_connections")
+		}
+	}
+
+	// Version recommendations
+	if classification.Category == "version" && ctx.DatabaseVersion != "" {
+		report.Recommendations = append(report.Recommendations,
+			fmt.Sprintf("Database version: %s", ctx.DatabaseVersion))
+		report.Recommendations = append(report.Recommendations,
+			"• Check backup was created on same or older PostgreSQL version")
+		report.Recommendations = append(report.Recommendations,
+			"• For major version differences, review migration notes")
+	}
+}
+
+// analyzeRootCause attempts to determine the root cause based on error + context
+func analyzeRootCause(report *DiagnosticsReport) string {
+	ctx := report.Context
+	classification := report.Classification
+
+	// Disk space root causes
+	if classification.Category == "disk_space" {
+		if ctx.DiskUsagePercent > 95 {
+			return "Disk is critically full - no space for backup/restore operations"
+		}
+		return "Insufficient disk space for operation"
+	}
+
+	// Lock exhaustion root causes
+	if classification.Category == "locks" {
+		if ctx.MaxLocksPerTxn > 0 && ctx.MaxConnections > 0 {
+			totalLocks := ctx.MaxLocksPerTxn * (ctx.MaxConnections + 100)
+			if totalLocks < 50000 {
+				return fmt.Sprintf("Lock table capacity too low (%d total locks). Likely cause: max_locks_per_transaction (%d) too low for this database size",
+					totalLocks, ctx.MaxLocksPerTxn)
+			}
+		}
+		return "PostgreSQL lock table exhausted - need to increase max_locks_per_transaction"
+	}
+
+	// Memory pressure
+	if ctx.MemoryUsagePercent > 90 {
+		return "System under memory pressure - may cause slow operations or failures"
+	}
+
+	// Connection exhaustion
+	if classification.Category == "network" && ctx.MaxConnections > 0 && ctx.CurrentConnections > 0 {
+		if ctx.CurrentConnections >= ctx.MaxConnections {
+			return "Connection pool exhausted - all connections in use"
+		}
+	}
+
+	return ""
+}
+
+// FormatDiagnosticsReport creates a human-readable diagnostics report
+func FormatDiagnosticsReport(report *DiagnosticsReport) string {
+	var sb strings.Builder
+
+	sb.WriteString("═══════════════════════════════════════════════════════════\n")
+	sb.WriteString("  DBBACKUP ERROR DIAGNOSTICS REPORT\n")
+	sb.WriteString("═══════════════════════════════════════════════════════════\n\n")
+
+	// Error classification
+	sb.WriteString(fmt.Sprintf("Error Type: %s\n", strings.ToUpper(report.Classification.Type)))
+	sb.WriteString(fmt.Sprintf("Category:   %s\n", report.Classification.Category))
+	sb.WriteString(fmt.Sprintf("Severity:   %d/3\n\n", report.Classification.Severity))
+
+	// Error message
+	sb.WriteString("Message:\n")
+	sb.WriteString(fmt.Sprintf("  %s\n\n", report.Classification.Message))
+
+	// Hint
+	if report.Classification.Hint != "" {
+		sb.WriteString("Hint:\n")
+		sb.WriteString(fmt.Sprintf("  %s\n\n", report.Classification.Hint))
+	}
+
+	// Root cause (if identified)
+	if report.RootCause != "" {
+		sb.WriteString("Root Cause:\n")
+		sb.WriteString(fmt.Sprintf("  %s\n\n", report.RootCause))
+	}
+
+	// System context
+	sb.WriteString("System Context:\n")
+	sb.WriteString(fmt.Sprintf("  Disk Space:  %s / %s (%.1f%% used)\n",
+		formatBytes(report.Context.AvailableDiskSpace),
+		formatBytes(report.Context.TotalDiskSpace),
+		report.Context.DiskUsagePercent))
+	sb.WriteString(fmt.Sprintf("  Memory:      %s / %s (%.1f%% used)\n",
+		formatBytes(report.Context.AvailableMemory),
+		formatBytes(report.Context.TotalMemory),
+		report.Context.MemoryUsagePercent))
+
+	if report.Context.OpenFileDescriptors > 0 {
+		sb.WriteString(fmt.Sprintf("  File Descriptors: %d / %d\n",
+			report.Context.OpenFileDescriptors,
+			report.Context.MaxFileDescriptors))
+	}
+
+	// Database context
+	if report.Context.DatabaseVersion != "" {
+		sb.WriteString("\nDatabase Context:\n")
+		sb.WriteString(fmt.Sprintf("  Version:     %s\n", report.Context.DatabaseVersion))
+		if report.Context.MaxConnections > 0 {
+			sb.WriteString(fmt.Sprintf("  Connections: %d / %d\n",
+				report.Context.CurrentConnections,
+				report.Context.MaxConnections))
+		}
+		if report.Context.MaxLocksPerTxn > 0 {
+			sb.WriteString(fmt.Sprintf("  Max Locks:   %d per transaction\n", report.Context.MaxLocksPerTxn))
+			totalLocks := report.Context.MaxLocksPerTxn * (report.Context.MaxConnections + 100)
+			sb.WriteString(fmt.Sprintf("  Total Lock Capacity: ~%d\n", totalLocks))
+		}
+		if report.Context.SharedMemory != "" {
+			sb.WriteString(fmt.Sprintf("  Shared Memory: %s\n", report.Context.SharedMemory))
+		}
+	}
+
+	// Recommendations
+	if len(report.Recommendations) > 0 {
+		sb.WriteString("\nRecommendations:\n")
+		for _, rec := range report.Recommendations {
+			sb.WriteString(fmt.Sprintf("  %s\n", rec))
+		}
+	}
+
+	// Action
+	if report.Classification.Action != "" {
+		sb.WriteString("\nSuggested Action:\n")
+		sb.WriteString(fmt.Sprintf("  %s\n", report.Classification.Action))
+	}
+
+	sb.WriteString("\n═══════════════════════════════════════════════════════════\n")
+	sb.WriteString(fmt.Sprintf("Report generated: %s\n", report.Context.CollectedAt.Format("2006-01-02 15:04:05")))
+	sb.WriteString("═══════════════════════════════════════════════════════════\n")
+
+	return sb.String()
+}

internal/database/interface.go

@@ -117,6 +117,10 @@ func (b *baseDatabase) Close() error {
 	return nil
 }
 
+func (b *baseDatabase) GetConn() *sql.DB {
+	return b.db
+}
+
 func (b *baseDatabase) Ping(ctx context.Context) error {
 	if b.db == nil {
 		return fmt.Errorf("database not connected")

internal/database/postgresql.go

@@ -339,8 +339,9 @@ func (p *PostgreSQL) BuildBackupCommand(database, outputFile string, options Bac
 		cmd = append(cmd, "--compress="+strconv.Itoa(options.Compression))
 	}
 
-	// Parallel jobs (only for directory format)
-	if options.Parallel > 1 && options.Format == "directory" {
+	// Parallel jobs (supported for directory and custom formats since PostgreSQL 9.3)
+	// NOTE: plain format does NOT support --jobs (it's single-threaded by design)
+	if options.Parallel > 1 && (options.Format == "directory" || options.Format == "custom") {
 		cmd = append(cmd, "--jobs="+strconv.Itoa(options.Parallel))
 	}
 

main.go

@@ -16,7 +16,7 @@ import (
 
 // Build information (set by ldflags)
 var (
-	version   = "4.2.8"
+	version   = "4.2.15"
 	buildTime = "unknown"
 	gitCommit = "unknown"
 )