# LVM Migration Guide: Live USB to LVM System

## Overview

This guide provides comprehensive instructions for migrating your current non-LVM system to an LVM-based system on an external M.2 SSD. **This migration MUST be performed from a live USB system** to avoid file system conflicts and ensure data integrity.

## Why Migrate to LVM?

**Benefits of LVM System:**
- **Instant Snapshots**: Create consistent backups without downtime
- **Flexible Storage**: Resize volumes dynamically without repartitioning
- **Advanced Backups**: Snapshot-based backups with rollback capability
- **Space Efficiency**: Snapshots only store changes, not full copies
- **System Recovery**: Easy rollback to previous states

## Prerequisites

### Hardware Requirements
- **Live USB System**: Boot from any Linux live USB (Ubuntu, Debian, etc.)
- **Internal Drive**: Your current system (will remain unchanged)
- **External M.2 SSD**: Target drive for LVM system (will be formatted)
- **Sufficient Space**: External drive should be ≥ size of used space on internal drive

### Software Requirements
- Live USB system with LVM tools (will be installed automatically)
- Network connection for package installation
- Root/sudo access on live system

## Before You Begin

### 1. Create Recovery Environment
```bash
# Prepare live USB with migration tools
# Download latest Ubuntu/Debian live ISO
# Flash to USB drive using dd or balenaEtcher
```

### 2. Backup Important Data
⚠️ **CRITICAL**: While the internal drive remains unchanged, create an additional backup of critical data before proceeding.

### 3. Document Current System
```bash
# Boot your current system and document the configuration
lsblk -f > system_layout.txt
df -h > disk_usage.txt
cat /etc/fstab > fstab_backup.txt
```

## Migration Process

### Step 1: Boot from Live USB System

1. **Shutdown your system** completely
2. **Insert live USB** and connect external M.2 SSD
3. **Configure BIOS/UEFI**:
   - Set USB as first boot device
   - Ensure both internal and external drives are detected
4. **Boot live system**:
   - Select "Try Ubuntu" or "Live System" (not "Install")
   - Wait for desktop to load completely
5. **Open terminal** and gain root access:
   ```bash
   sudo -i
   ```

### Step 2: Prepare Live System

```bash
# Download and prepare the migration tools
cd /tmp
git clone <your-repo> backup_tools
cd backup_tools

# Or if you have the tools on external drive already:
mkdir -p /mnt/temp
mount /dev/sda1 /mnt/temp  # Adjust device as needed
cp -r /mnt/temp/migration_tools/* /tmp/
umount /mnt/temp

# Prepare the live system
./prepare_live_system.sh
```

**This script will:**
- ✅ Verify you're running from live system
- 📦 Install required packages (lvm2, cryptsetup, rsync, etc.)
- 🔧 Load kernel modules for LVM
- 💽 Detect available drives
- 📁 Create migration workspace

### Step 3: Run Migration Script

```bash
# Execute the migration (this will take 30-90 minutes)
./migrate_to_lvm.sh
```

**The migration process includes:**

1. **Drive Detection** (Automatic):
   ```
   Detecting drives...
   Available drives:
   1. /dev/nvme0n1 - 477GB Samsung SSD 980 (Internal)
   2. /dev/sda - 477GB Samsung T7 (External USB)
   
   Selected drives:
   Internal (source): /dev/nvme0n1
   External (target): /dev/sda
   ```

2. **System Analysis**:
   - Automatically detects partition layout
   - Identifies filesystem types
   - Handles encrypted partitions
   - Calculates optimal LVM sizes

3. **Confirmation Prompts**:
   ```
   ⚠️  WARNING: This will DESTROY all data on /dev/sda!
   
   Migration Summary:
   Source: /dev/nvme0n1 (non-LVM system)
   Target: /dev/sda (will become LVM system)
   Root size: 70G
   Home size: 350G
   Swap size: 16G
   Boot size: 2G
   
   Do you want to continue? [y/N]
   ```

4. **LVM Layout Creation**:
   - Creates GPT partition table
   - EFI boot partition (512MB)
   - LVM physical volume (remaining space)
   - Creates volume group and logical volumes

5. **Data Migration**:
   - Mounts source filesystems (handles encryption)
   - Copies all system data with rsync
   - Preserves permissions, links, and attributes
   - Updates system configuration files

6. **System Configuration**:
   - Updates /etc/fstab for LVM volumes
   - Configures initramfs for LVM support
   - Installs and configures GRUB bootloader
   - Creates LVM snapshot backup tools

### Step 4: Validation and Testing

```bash
# Validate the migration
./validate_lvm_migration.sh
```

**Validation checks:**
- ✅ LVM volumes created correctly
- ✅ Filesystems are healthy
- ✅ Boot configuration is valid
- ✅ GRUB installation successful
- ✅ System files copied completely
- ✅ LVM snapshot capability working

### Step 5: First Boot Test

1. **Cleanup and shutdown**:
   ```bash
   # Clean up and prepare for reboot
   sync
   umount -a
   shutdown -h now
   ```

2. **Configure BIOS/UEFI**:
   - Boot into BIOS/UEFI settings
   - Change boot order: External M.2 SSD as first boot device
   - Save and exit

3. **Test boot from external M.2**:
   - System should boot normally from external drive
   - Login and verify everything works
   - Check that all your files and settings are present

4. **Verify LVM system**:
   ```bash
   # Check LVM status
   sudo lvs
   sudo vgs
   sudo pvs
   
   # Check filesystem mounts
   df -h
   cat /proc/mounts | grep mapper
   ```

## System Configuration Details

### LVM Layout Created
```
Physical Volume: /dev/sda2
Volume Group: system-vg
Logical Volumes:
├── root (70G) - ext4 - mounted at /
├── home (350G) - ext4 - mounted at /home  
├── boot (2G) - ext4 - mounted at /boot
└── swap (16G) - swap - swap space

Additional:
├── /dev/sda1 (512M) - vfat - EFI boot partition - mounted at /boot/efi
└── Free space (~38G) - available for snapshots and volume expansion
```

### Migration Advantages

**Flexibility:**
- Resize any volume without repartitioning
- Add new drives to volume group
- Move logical volumes between physical drives

**Backup & Recovery:**
- Create instant snapshots of any volume
- Rollback changes using snapshots
- Consistent backups without downtime

**Space Management:**
- Thin provisioning support
- Automatic space allocation
- Easy expansion and shrinking

## Using LVM Snapshots

### Basic Snapshot Operations

```bash
# Create snapshots for backup
sudo ./lvm_snapshot_backup.sh backup

# Snapshots are mounted at:
/mnt/backup/root  # Snapshot of root filesystem
/mnt/backup/home  # Snapshot of home filesystem
/mnt/backup/boot  # Snapshot of boot filesystem

# Perform backup to external storage
rsync -avH /mnt/backup/ /path/to/external/backup/

# Clean up snapshots
sudo ./lvm_snapshot_backup.sh remove
```

### Advanced LVM Operations

```bash
# Extend a logical volume (add 10GB to home)
sudo lvextend -L +10G /dev/system-vg/home
sudo resize2fs /dev/system-vg/home

# Create additional logical volume
sudo lvcreate -L 20G -n data system-vg
sudo mkfs.ext4 /dev/system-vg/data
sudo mkdir /data
sudo mount /dev/system-vg/data /data

# Snapshot before system changes
sudo lvcreate -L 5G -s -n root-before-update /dev/system-vg/root

# Rollback if needed
sudo umount /
sudo lvconvert --merge /dev/system-vg/root-before-update
# Reboot to activate rollback
```

## Troubleshooting Guide

### Migration Issues

**Migration Script Fails**
```bash
# Check logs for detailed error information
tail -f /var/log/lvm-migration.log

# Common issues and solutions:
```

| Issue | Cause | Solution |
|-------|-------|----------|
| "Drive not found" | Drive not connected/detected | Check connections, try different USB port |
| "Insufficient space" | Target drive too small | Use larger drive or reduce partition sizes |
| "LVM tools not found" | Missing packages | Run `prepare_live_system.sh` first |
| "Permission denied" | Not running as root | Use `sudo` or `sudo -i` |
| "Mount failed" | Filesystem corruption | Check drive with `fsck` |

**Encrypted Partition Issues**
```bash
# If encrypted partition unlock fails:
sudo cryptsetup luksOpen /dev/nvme0n1p3 temp-unlock
# Enter correct password
sudo cryptsetup close temp-unlock
```

**Drive Detection Problems**
```bash
# Manually check drives
lsblk -dpno NAME,SIZE,MODEL
sudo fdisk -l

# If drives not detected:
sudo partprobe  # Re-read partition tables
sudo udevadm settle  # Wait for device detection
```

### Boot Issues After Migration

**System Won't Boot from External Drive**

1. **Check BIOS/UEFI Settings**:
   - Verify external M.2 is detected in BIOS
   - Set correct boot priority
   - Enable UEFI boot mode
   - Disable Secure Boot if necessary

2. **Repair GRUB from Live USB**:
   ```bash
   # Boot from live USB and mount LVM system
   sudo vgchange -ay system-vg
   sudo mount /dev/system-vg/root /mnt
   sudo mount /dev/system-vg/boot /mnt/boot
   sudo mount /dev/sda1 /mnt/boot/efi
   
   # Reinstall GRUB
   sudo mount --bind /dev /mnt/dev
   sudo mount --bind /proc /mnt/proc
   sudo mount --bind /sys /mnt/sys
   sudo chroot /mnt
   grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian
   update-grub
   exit
   
   # Cleanup and reboot
   sudo umount /mnt/dev /mnt/proc /mnt/sys
   sudo umount /mnt/boot/efi /mnt/boot /mnt
   sudo reboot
   ```

**Emergency Recovery**

If external system is completely broken:
1. Change BIOS boot order back to internal drive
2. Boot from original system (unchanged)
3. Re-attempt migration or continue with original system

### LVM Issues

**Volume Group Not Found**
```bash
# Activate volume group manually
sudo vgchange -ay system-vg

# Scan for volume groups
sudo vgscan
sudo pvscan
```

**Snapshot Issues**
```bash
# Remove stuck snapshots
sudo umount /mnt/backup/root /mnt/backup/home 2>/dev/null || true
sudo lvremove -f system-vg/root-snapshot
sudo lvremove -f system-vg/home-snapshot

# Check volume group free space
sudo vgs system-vg
```

**File System Corruption**
```bash
# Check and repair LVM volumes
sudo fsck /dev/system-vg/root
sudo fsck /dev/system-vg/home
sudo fsck /dev/system-vg/boot
```

## Recovery Procedures

### Complete Rollback to Original System

If you decide to abandon LVM migration:

1. **Boot from internal drive**:
   - Change BIOS boot order to internal drive
   - Boot normally from original system

2. **Reformat external drive** (optional):
   ```bash
   # Wipe LVM configuration
   sudo dd if=/dev/zero of=/dev/sda bs=1M count=100
   # Or use backup tools to restore external drive
   ```

3. **Continue with original system**:
   - Everything remains as before migration
   - Use existing backup tools for regular backups

### Retry Migration

If you want to attempt migration again:

1. **Boot from live USB**
2. **Run migration script again**:
   ```bash
   ./migrate_to_lvm.sh
   ```
   - Script will destroy existing LVM setup and recreate
   - Source system (internal) remains unchanged

### Disaster Recovery

**If both systems fail:**

1. **Boot from live USB**
2. **Mount internal drive** for data recovery:
   ```bash
   mkdir -p /mnt/recovery
   
   # Mount root partition
   sudo mount /dev/nvme0n1p1 /mnt/recovery
   
   # If home is encrypted:
   sudo cryptsetup open /dev/nvme0n1p3 recovery-home
   sudo mkdir -p /mnt/recovery/home
   sudo mount /dev/mapper/recovery-home /mnt/recovery/home
   
   # Copy important data to external storage
   rsync -avH /mnt/recovery/home/username/ /path/to/safe/backup/
   ```

3. **Fresh OS installation** if needed:
   - Install fresh OS on any drive
   - Restore personal data from backup

## Performance Optimization

### LVM Performance Tuning

```bash
# Enable read-ahead for better performance
sudo blockdev --setra 2048 /dev/system-vg/root
sudo blockdev --setra 2048 /dev/system-vg/home

# Add to /etc/fstab for persistent read-ahead:
# /dev/system-vg/root / ext4 defaults,noatime 0 1
# /dev/system-vg/home /home ext4 defaults,noatime 0 2
```

### Snapshot Management

```bash
# Monitor snapshot usage
sudo lvs -a -o lv_name,lv_size,data_percent system-vg

# Remove old snapshots regularly
sudo lvremove system-vg/old-snapshot-name

# Set up automatic snapshot cleanup (cron job)
echo '0 2 * * * root /usr/local/bin/lvm-snapshot-backup.sh remove' >> /etc/crontab
```

## Best Practices

### Regular Maintenance

1. **Monitor disk space**:
   ```bash
   sudo vgs system-vg  # Check volume group free space
   df -h  # Check filesystem usage
   ```

2. **Regular snapshots**:
   ```bash
   # Before system updates
   sudo lvcreate -L 5G -s -n pre-update-$(date +%Y%m%d) /dev/system-vg/root
   
   # Before major changes
   sudo ./lvm_snapshot_backup.sh backup
   ```

3. **Backup strategy**:
   - Daily: LVM snapshots to external storage
   - Weekly: Full system backup using existing tools
   - Monthly: Verify backup integrity

### Security Considerations

- **Encryption**: Home data is no longer encrypted in LVM setup
  - Consider full disk encryption if security is critical
  - Use file-level encryption for sensitive data

- **Access Control**: Secure LVM management commands
  ```bash
  # Restrict LVM command access
  sudo chmod 750 /usr/local/bin/lvm-*
  ```

## Summary

The migration successfully transforms your system from traditional partitions to a flexible LVM-based setup, providing:

✅ **Instant snapshots** for consistent backups  
✅ **Dynamic volume resizing** without downtime  
✅ **Advanced backup strategies** with rollback capability  
✅ **Space efficiency** with thin provisioning  
✅ **System recovery** options with snapshots  

Your original system remains intact as a fallback, making this a low-risk enhancement to your backup and storage capabilities.