[nix-book] Add btrfs migration plan
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machines/nix-book/nixbook-btrfs-migration.md
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machines/nix-book/nixbook-btrfs-migration.md
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# NixBook ext4 to btrfs Migration Guide
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## Overview
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This guide converts your nixbook machine from ext4 to btrfs with zstd compression and beesd deduplication while preserving your LUKS encryption and all data.
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## Current System Info
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- **Hostname**: nix-book
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- **Root filesystem**: ext4 on `/dev/disk/by-uuid/bd396529-e2c4-47cb-b844-8d6ed841f81a`
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- **Encryption**: LUKS with two devices configured
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- **Current usage**: 138GB used / 225GB total (65% full)
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- **Free space**: 76GB available (sufficient for conversion)
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## Pre-Migration Checklist
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### 1. Create Full System Backup (CRITICAL)
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```bash
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# Boot from NixOS live USB
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# Mount encrypted filesystem
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cryptsetup luksOpen /dev/disk/by-uuid/4126fbd4-bd09-4ece-af0d-6fff414c21b3 luks-nixbook
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mount /dev/mapper/luks-nixbook /mnt
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# Create backup to external drive (adjust target as needed)
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rsync -avxHAX --progress /mnt/ /path/to/backup/nixbook-backup/
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```
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### 2. Verify Configuration Changes
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The following files have been updated for btrfs:
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- `machines/nix-book/configuration.nix` - Added beesd service
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- `machines/nix-book/hardware-configuration.nix` - Changed fsType to btrfs with compression
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## Migration Process
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### Phase 1: Boot to Live Environment
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1. **Create NixOS live USB**:
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```bash
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# Download latest NixOS ISO
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# Flash to USB drive
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dd if=nixos-minimal-xx.xx-x86_64-linux.iso of=/dev/sdX bs=4M status=progress
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```
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2. **Boot from live USB** and ensure you can access the encrypted drives
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### Phase 2: Filesystem Conversion
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3. **Unlock LUKS volumes**:
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```bash
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cryptsetup luksOpen /dev/disk/by-uuid/4126fbd4-bd09-4ece-af0d-6fff414c21b3 luks-nixbook
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cryptsetup luksOpen /dev/disk/by-uuid/b614167b-9045-4234-a441-ac6f60a96d81 luks-nixbook2
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```
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4. **Check filesystem before conversion**:
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```bash
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fsck.ext4 -f /dev/mapper/luks-nixbook
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```
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5. **Convert ext4 to btrfs** (this preserves all data):
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```bash
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# Install btrfs-progs if not available
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nix-shell -p btrfs-progs
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# Convert the filesystem (takes 15-45 minutes depending on data)
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btrfs-convert /dev/mapper/luks-nixbook
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# Verify conversion succeeded
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mount /dev/mapper/luks-nixbook /mnt
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ls -la /mnt # Should show your normal filesystem
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btrfs filesystem show /mnt
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```
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6. **Get new filesystem UUID** (may have changed):
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```bash
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blkid /dev/mapper/luks-nixbook
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# Note the new UUID if it changed
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```
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### Phase 3: Configuration Update
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7. **Mount and chroot into system**:
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```bash
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mount -o compress=zstd,noatime /dev/mapper/luks-nixbook /mnt
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mount /dev/disk/by-uuid/7A0B-CF88 /mnt/boot
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nixos-enter --root /mnt
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```
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8. **Update hardware-configuration.nix** if UUID changed:
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```bash
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# Edit /etc/nixos/hardware-configuration.nix if needed
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# Update the UUID in fileSystems."/" section
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```
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9. **Rebuild system with btrfs configuration**:
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```bash
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cd /home/johno/nixos-configs
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nixos-rebuild switch --flake .#nix-book
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```
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### Phase 4: Enable Compression and Deduplication
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10. **Reboot into new btrfs system**:
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```bash
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exit # Exit chroot
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umount -R /mnt
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reboot
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```
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11. **Verify btrfs is working**:
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```bash
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mount | grep btrfs
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btrfs filesystem usage /
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```
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12. **Enable and start beesd**:
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```bash
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systemctl status beesd-root
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systemctl start beesd-root
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systemctl enable beesd-root
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```
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13. **Force compression on existing files** (optional but recommended):
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```bash
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# This will compress existing files with zstd
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btrfs filesystem defragment -r -czstd /
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```
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## Post-Migration Verification
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### Check System Health
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```bash
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# Verify btrfs health
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btrfs scrub start /
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btrfs scrub status /
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# Check compression effectiveness
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compsize /
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# Monitor beesd deduplication
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journalctl -u beesd-root -f
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# Check filesystem usage
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btrfs filesystem usage /
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df -h /
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```
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### Performance Monitoring
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```bash
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# Monitor beesd hash table
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ls -lh /.beeshash
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# Check compression ratio over time
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compsize /home /nix /var
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```
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## Expected Benefits
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### Space Savings
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- **Compression**: 20-30% reduction in disk usage from zstd
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- **Deduplication**: Additional 10-20% savings on duplicate files
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- **Combined**: Potentially 30-40% total space savings
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### Performance Impact
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- **Compression**: Minimal CPU overhead, often improves I/O performance
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- **Deduplication**: Background process, minimal impact during normal use
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- **Overall**: Should be neutral to positive performance impact
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## Rollback Plan (Emergency)
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If something goes wrong:
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1. **Boot from live USB**
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2. **Restore from backup**:
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```bash
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cryptsetup luksOpen /dev/disk/by-uuid/4126fbd4-bd09-4ece-af0d-6fff414c21b3 luks-nixbook
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mkfs.ext4 /dev/mapper/luks-nixbook
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mount /dev/mapper/luks-nixbook /mnt
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rsync -avxHAX --progress /path/to/backup/nixbook-backup/ /mnt/
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```
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3. **Restore original hardware-configuration.nix** with ext4 settings
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4. **Rebuild and reboot**
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## Troubleshooting
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### Common Issues
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**"Device busy" during conversion**:
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- Ensure no processes are accessing the filesystem
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- Check with `lsof` and `fuser`
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**UUID changed after conversion**:
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- Update hardware-configuration.nix with new UUID
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- Regenerate initrd: `nixos-rebuild switch`
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**Beesd service fails to start**:
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- Check disk space for hash table
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- Verify filesystem is btrfs: `mount | grep btrfs`
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- Check logs: `journalctl -u beesd-root`
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**Boot issues after conversion**:
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- Boot from live USB
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- Check /boot partition is mounted correctly
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- Verify LUKS UUIDs match in configuration
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- Rebuild bootloader: `nixos-rebuild switch --install-bootloader`
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## Maintenance
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### Regular Tasks
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```bash
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# Monthly scrub (checks for corruption)
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btrfs scrub start /
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# Monitor compression effectiveness
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compsize /
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# Check beesd deduplication status
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systemctl status beesd-root
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```
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### Space Management
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```bash
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# Balance filesystem (defragments and optimizes)
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btrfs balance start -dusage=50 /
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# Check for space issues
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btrfs filesystem usage /
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```
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This migration preserves all your data while gaining the benefits of modern btrfs features including transparent compression and automatic deduplication.
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Reference in New Issue
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