---
tags:
  - Rclone
  - PowerShell
  - Synchronization
  - Google Drive
---

## Purpose
This document explains the practical differences between the rclone `copy`, `sync`, `check`, and `bisync` commands and links to the separate workflow for configuring and recovering a bidirectional synchronization pair.  The examples use PowerShell and assume that one side of the synchronization is a Google Drive remote.

Rclone is a command-line file-management program that supports cloud storage providers, object-storage platforms, local filesystems, and standard transfer protocols.

[Download rClone](https://rclone.org/downloads)

[Official rClone Documentation](https://rclone.org/docs/)

!!! info "Version Context"
    This document was reviewed against rclone `v1.75.0`.  Older releases may not support every bisync flag documented here, and future versions may change some recovery behavior.

!!! danger "Rclone Can Delete or Overwrite Data"
    The `sync` and `bisync` commands can delete, replace, rename, or propagate the deletion of files.  Always confirm the source and destination paths, maintain a separate backup or snapshot, and preview unfamiliar operations with `--dry-run` before allowing them to modify data.

    A dry run is a preview and is not a replacement for a backup.

## Prepare the Command
Set the executable path in the PowerShell session before using the command examples.  Replace the example path with the location of `rclone.exe` on the target machine.

```powershell
$Rclone = "C:\Path\To\rclone.exe"
```

## Command Behavior
The correct command depends on the intended relationship between the source and destination.

| **Command** | **Primary Behavior** | **Deletes Destination-Only Files** | **Direction** |
| :--- | :--- | :--- | :--- |
| `copy` | Adds or updates source files at the destination while retaining unrelated destination files | No | One-way |
| `sync` | Makes the destination match the source | Yes | One-way |
| `check` | Compares files without modifying either side | No | Read-only |
| `bisync` | Detects and propagates changes made on either side by comparing the current state against prior listings | Yes | Two-way |

### Use `copy` for Additive Transfers
Use `copy` when you need to add or update files without deleting files that already exist only at the destination.

```powershell
& $Rclone copy "Source" "Destination" --update --dry-run --verbose
```

The `--update` flag skips a source file when the corresponding destination file has a newer modification time.  It does not create version history, and it does not prevent an older destination file from being replaced by a newer source file.

After reviewing the dry-run output, repeat the operation without `--dry-run`:

```powershell
& $Rclone copy "Source" "Destination" --update --verbose
```

### Use `sync` Only for Intentional Mirroring
Use `sync` when the destination must become a one-way mirror of the source.

!!! danger "`sync` Deletes Destination-Only Files"
    The `sync` command removes files from the destination when they do not exist in the source.  This is true even when `--update` is present.

    The `--update` flag only prevents a newer destination file from being replaced by an older source file.  It does not convert `sync` into an additive operation and does not protect destination-only files from deletion.

Preview the operation first:

```powershell
& $Rclone sync "Source" "Destination" --dry-run --verbose
```

Only remove `--dry-run` after confirming that every proposed copy, replacement, and deletion is intentional:

```powershell
& $Rclone sync "Source" "Destination" --verbose
```

### Use `check` for Read-Only Comparison
The `check` command compares files on both sides without copying, replacing, or deleting them.

```powershell
& $Rclone check "Source" "Destination" --combined "rclone-comparison.txt" --log-level INFO --log-file "rclone-check.log"
```

The combined report uses the following symbols:

| **Symbol** | **Meaning** |
| :--- | :--- |
| `=` | The file exists on both sides and matches |
| `+` | The file exists only in the source |
| `-` | The file exists only in the destination |
| `*` | The same path exists on both sides, but the files differ |
| `!` | The file could not be read or compared |

The `check` command compares files but does not report missing empty directories.

## Configure Two-Way Synchronization
Use [Configure and Recover Rclone Bisync](<../../../workflows/Applications/Files and Collaboration/Configure and Recover Rclone Bisync.md>) for initialization, normal runs, state handling, and recovery.

## Related Documentation
- [Related Files and Collaboration Documentation](<index.md>) — Find the connected deployments, procedures, and references for this subject.