Sync

Synchronize files and directories between local, remote, and cloud storage reliably.

Security Scan

The skill is an instruction-only helper for rsync/rclone-style file synchronization and its requested resources and instructions are consistent with that purpose.

Purpose & Capability

Name and description match the SKILL.md. The only runtime requirements declared are rsync or rclone binaries, which are exactly what a sync helper would need.

Instruction Scope

SKILL.md contains concrete, narrowly-scoped guidance for rsync, rclone, unison, and SSH usage. It does not instruct the agent to read unrelated system files, harvest credentials, or post data to unexpected endpoints. It explicitly advises not to hardcode cloud credentials.

Install Mechanism

No install spec and no code files — this is instruction-only, so nothing is downloaded or written to disk by the skill itself.

Credentials

The skill declares no environment variables or credentials, and the instructions only reference normal user paths (e.g., ~/.ssh/key) appropriate for SSH-based sync. No unrelated secrets are requested.

Persistence & Privilege

Skill is not always-enabled and does not request persistent modifications. It relies on user-invoked commands and therefore does not require elevated or permanent privileges.

Assessment

This skill is a text-only set of best-practices for using rsync/rclone/unison — it does not include code or request credentials. Still, be mindful: if you let an agent execute these commands, those commands can read and modify local files and contact remote hosts. Before running any destructive sync (especially with --delete or rclone sync), run --dry-run and inspect the exact command the agent will run. Ensure rsync/rclone on your system are the versions you expect, and never let the agent hardcode cloud credentials into scripts. If you prefer, run the suggested commands yourself rather than allowing autonomous execution.

File Synchronization Rules

rsync Fundamentals

• Trailing slash matters: rsync src/ copies contents, rsync src copies the folder itself — this is the #1 cause of wrong directory structures
• Always use -avz baseline: archive mode preserves permissions/timestamps, verbose shows progress, compress speeds transfers
• Add --delete only when you want destination to mirror source exactly — without it, deleted source files remain on destination
• Use --dry-run before any destructive sync — shows what would change without modifying anything

Exclusions

• Create an exclude file instead of multiple --exclude flags: rsync -avz --exclude-from=.syncignore src/ dest/
• Standard excludes for code projects: .git/, node_modules/, __pycache__/, .venv/, *.pyc, .DS_Store, Thumbs.db
• Exclude patterns are relative to source root — /logs/ excludes only top-level logs, logs/ excludes logs/ anywhere

Cloud Storage (rclone)

• rclone sync deletes destination files not in source; rclone copy only adds — use copy when unsure
• Configure remotes interactively: rclone config — never hardcode cloud credentials in scripts
• Test with --dry-run first, then --progress for visual feedback during actual sync
• For S3-compatible storage, set --s3-chunk-size 64M for large files to avoid timeouts

Verification

• After critical syncs, verify with checksums: rsync -avzc uses checksums instead of size/time (slower but certain)
• For rclone, use rclone check source: dest: to compare without transferring
• Log sync operations to file for audit: rsync -avz src/ dest/ | tee sync.log

Bidirectional Sync

• rsync is one-way only — for true bidirectional sync, use unison: unison dir1 dir2
• Unison detects conflicts when both sides change — resolve manually or set prefer rules
• Cloud services like Dropbox/Syncthing handle bidirectional automatically — don't reinvent with rsync

Remote Sync

• For SSH remotes, use key-based auth: rsync -avz -e "ssh -i ~/.ssh/key" src/ user@host:dest/
• Specify non-standard SSH port: -e "ssh -p 2222"
• Use --partial --progress for large files over unreliable connections — allows resume on failure

Common Pitfalls

• Syncing to mounted drives that unmount silently creates a local folder with the mount name — verify mount before sync
• Running sync without --delete repeatedly causes destination to accumulate deleted files forever
• Time-based sync fails across machines with clock skew — use --checksum for accuracy or sync NTP first