Sync Migrations

Sync Migrations

One-time scripts that run on existing machines when dotfiles changes require cleanup.

When to Use

Create migration for:

• Removing/uninstalling replaced tools (npm → brew)
• Deleting deprecated files/directories
• Cleaning stale symlinks

Don't create for:

• Adding new configs (sync handles this)
• Updating existing configs (symlinks auto-update)

Quick Reference

CLI Flags

Creating a Migration

#!/bin/bash
set -e

# Always check before acting (idempotent)
if [ -d ~/.old-thing ]; then
    rm -rf ~/.old-thing
fi

if command -v old-tool &>/dev/null; then
    brew uninstall old-tool
fi

Requirements:

• Timestamped filename: YYYY-MM-DD-description.sh
• set -e for fail-fast
• Idempotent checks before each action
• Make executable: chmod +x

How It Works

1. Marker file stores last-run date
2. Migrations with timestamp > marker are pending
3. User confirms before running
4. Marker updates after each success

New machines: No marker = all pending. User decides to run or skip (fresh setup doesn't need cleanup).

Troubleshooting Failures

When a migration fails, help the user recover:

1. Read the failed migration script to understand intent
2. Check the sync log at /tmp/dotfiles-sync-*.log for error details
3. Diagnose the issue - missing dependency, permission error, path doesn't exist, etc.
4. Options:
   • Fix the issue and re-run: ./sync --migrate-only
   • Run commands manually, then update marker: echo "YYYY-MM-DD" > ~/.dotfiles-migration-marker
   • Skip the migration entirely by advancing the marker past it

Common failure patterns:

• command not found → tool not installed, check Brewfile ran first
• permission denied → may need sudo (sync doesn't have it)
• No such file → path changed or doesn't exist on this machine (make script idempotent)

Recovery example:

# Migration 2025-01-10-foo.sh failed
# Fix: run the commands manually
brew uninstall old-thing  # or whatever failed

# Then advance marker so it won't retry
echo "2025-01-10" > ~/.dotfiles-migration-marker