# GRUB Repair Quick Reference

## Essential Commands

### 1. System Detection
```bash
sudo ./grub-repair.sh detect
```
**What this does**: Shows all available disks, partitions, and identifies which ones are bootable Linux systems.
**When to use**: First step - always run this to see what systems are available before attempting repairs.
**Output**: Lists disks, partitions, filesystem types, and mount points.

### 2. Complete Boot Repair (Recommended)
```bash
sudo ./grub-repair.sh -d /dev/sda -p 1 -b fix-boot
```
**What this does**: Mounts your system, installs GRUB, updates configuration, and repairs EFI - all in one command with automatic backup.
**When to use**: Your system won't boot, GRUB is missing/corrupted, or you need a complete boot recovery.
**Device note**: Replace `/dev/sda` with your actual disk (use `lsblk` to find it).

### 3. Check Status
```bash
sudo ./grub-repair.sh status
```
**What this does**: Shows current mount status, available GRUB configurations, EFI partition status, and backup information.
**When to use**: After mounting or during troubleshooting to see what's currently available and mounted.
**Output**: Current system state, mounted filesystems, and backup locations.

### 4. Clean Up
```bash
sudo ./grub-repair.sh clean
```
**What this does**: Safely unmounts all systems, removes temporary mount points, and cleans up resources.
**When to use**: After completing repairs, when switching between systems, or if something goes wrong.
**Safety**: Automatically unmounts everything in the correct order to prevent data loss.

## Common Scenarios

### Fresh Boot Repair
```bash
# Detect your system first
sudo ./grub-repair.sh detect

# Then repair (replace /dev/sda with your device)
sudo ./grub-repair.sh -d /dev/sda -p 1 -b fix-boot
```
**Step-by-step process**:
1. **Detect**: Identify available systems and their locations
2. **Repair**: Complete boot repair with automatic backup
3. **Reboot**: Restart your system to test the repair

**Device identification**: Use `lsblk` or `fdisk -l` to find your disk name if unsure.

### GRUB Reinstall Only
```bash
# Mount system
sudo ./grub-repair.sh -d /dev/sda -p 1 mount

# Install GRUB
sudo ./grub-repair.sh install-grub

# Update config
sudo ./grub-repair.sh update-grub

# Unmount
sudo ./grub-repair.sh unmount
```
**When to use**: You only need to reinstall GRUB, not perform a complete repair.
**Manual control**: Gives you step-by-step control over the GRUB installation process.
**Safety**: Each step can be verified before proceeding to the next.

### EFI Partition Check and Repair
```bash
sudo ./grub-repair.sh -d /dev/sda check-efi
```
**What this does**: Checks EFI partition health, repairs boot entries, and creates new GRUB boot entries if needed.
**When to use**: EFI boot issues, missing boot entries, or when GRUB isn't showing up in UEFI boot menu.
**Advanced**: Automatically detects your Linux distribution for proper bootloader ID.

## Device Identification

- **Find your disk**: `lsblk` or `fdisk -l`
- **EFI partition**: Usually the first partition (e.g., `/dev/sda1`)
- **Root partition**: Usually the second partition (e.g., `/dev/sda2`)

**Common device names**:
- **SATA drives**: `/dev/sda`, `/dev/sdb`, `/dev/sdc`
- **NVMe drives**: `/dev/nvme0n1`, `/dev/nvme1n1`
- **USB drives**: `/dev/sdd`, `/dev/sde` (when booted from USB)

## Safety Tips

- **Always use `-b` flag for backup** - Creates automatic backups before making changes
- **Test on non-critical systems first** - Verify the script works in your environment
- **Keep live ISO handy for recovery** - You may need to boot from it again if issues arise
- **Document your partition layout** - Note down which partitions are which before starting
- **Use `-v` flag for verbose output** - Get detailed information during operations for troubleshooting

## Troubleshooting

- **Permission denied**: Use `sudo` - Script requires root access for system operations
- **Device not found**: Check with `lsblk` - Verify device names and partition layout
- **Mount fails**: Use `clean` command first - Cleans up any partial mounts
- **Verbose output**: Add `-v` flag - Shows detailed operation information
- **Force mode**: Use `-f` flag - Bypass live ISO detection if needed
- **Custom mount point**: Use `-m /path` - Specify custom mount location

## Additional Useful Commands

### Manual Mounting
```bash
# Mount a specific system
sudo ./grub-repair.sh -d /dev/sda -p 1 mount

# Unmount current system
sudo ./grub-repair.sh unmount

# Check what's mounted
sudo ./grub-repair.sh status
```

### Backup and Recovery
```bash
# Create backup only
sudo ./grub-repair.sh backup

# Check backup status
sudo ./grub-repair.sh status
```

### Advanced Options
```bash
# Force mode (bypass live ISO check)
sudo ./grub-repair.sh -f -d /dev/sda detect

# Verbose output for debugging
sudo ./grub-repair.sh -v -d /dev/sda check-efi

# Custom mount point
sudo ./grub-repair.sh -m /mnt/custom -d /dev/sda mount
```

## Quick Recovery Workflow

1. **Boot from Live ISO** - Start your system from a live Linux ISO
2. **Detect Systems** - `sudo ./grub-repair.sh detect`
3. **Identify Target** - Note the device name and partition number
4. **Complete Repair** - `sudo ./grub-repair.sh -d /dev/DEVICE -p PARTITION -b fix-boot`
5. **Clean Up** - `sudo ./grub-repair.sh clean`
6. **Reboot** - Restart and test your system

**Pro tip**: The `-b` flag creates automatic backups, so you can always restore if something goes wrong!