BackupWindowsToLinux

A PowerShell module for backing up files from Windows to remote Linux systems using native OpenSSH. Only transfers new or modified files for efficient incremental backups.

Features

• Incremental backups — Only transfers new or modified files (compares size + timestamp)
• Native OpenSSH — Uses Windows 10+ built-in SSH (no third-party modules needed)
• SSH key authentication — Secure, password-less backups
• Exclusion patterns — Skip files and directories by pattern (e.g., node_modules, .git, *.tmp)
• Orphaned cleanup — Optionally delete files/directories on remote that no longer exist locally
• Dry run mode — Preview changes without transferring
• Progress tracking — Real-time progress display
• Timestamp preservation — Maintains original file modification times

Prerequisites

Windows OpenSSH Client — Already installed on Windows 10/11 and Server 2019+

To verify:

ssh -V

If not installed:

Add-WindowsCapability -Online -Name OpenSSH.Client~~~~0.0.1.0

Installation

From PowerShell Gallery

Install-Module BackupWindowsToLinux

Manual

Copy the module folder to a directory in your $env:PSModulePath.

Quick Start

1. Set Up SSH Keys (One-time)

# Generate key
ssh-keygen -t ed25519 -f "$env:USERPROFILE\.ssh\id_ed25519" -C "backup@mypc"

# Copy to server
type "$env:USERPROFILE\.ssh\id_ed25519.pub" | ssh admin@192.168.1.100 "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"

# Test
ssh -i "$env:USERPROFILE\.ssh\id_ed25519" admin@192.168.1.100

2. Run Backup

Import-Module BackupWindowsToLinux

Sync-ToLinux `
    -Source "C:\Documents" `
    -Destination "/backup/documents" `
    -HostName "192.168.1.100" `
    -UserName "admin" `
    -KeyFile "$env:USERPROFILE\.ssh\id_ed25519"

Usage Examples

Basic Backup

Sync-ToLinux `
    -Source "C:\Data" `
    -Destination "/backup/data" `
    -HostName "myserver.com" `
    -UserName "admin" `
    -KeyFile "$env:USERPROFILE\.ssh\id_rsa"

Exclude Directories/Files

Sync-ToLinux `
    -Source "C:\Projects" `
    -Destination "/backup/projects" `
    -HostName "server.com" `
    -UserName "admin" `
    -KeyFile "$env:USERPROFILE\.ssh\id_rsa" `
    -ExcludePatterns @("node_modules", ".git", "bin", "obj", "*.tmp")

Dry Run (Preview)

Sync-ToLinux `
    -Source "C:\Data" `
    -Destination "/backup" `
    -HostName "192.168.1.100" `
    -UserName "admin" `
    -KeyFile "$env:USERPROFILE\.ssh\id_rsa" `
    -DryRun

Mirror Mode (Delete Orphans)

Sync-ToLinux `
    -Source "C:\Sync" `
    -Destination "/home/user/sync" `
    -HostName "nas.local" `
    -UserName "admin" `
    -KeyFile "$env:USERPROFILE\.ssh\id_rsa" `
    -DeleteOrphaned

Parameters

Parameter	Required	Description
Source	Yes	Local Windows path to backup
Destination	Yes	Remote Linux destination path
HostName	Yes	Remote server hostname or IP
UserName	Yes	SSH username
KeyFile	No	Path to SSH private key (recommended)
Port	No	SSH port (default: 22)
ExcludePatterns	No	Array of patterns to exclude
DryRun	No	Preview mode — don't transfer
DeleteOrphaned	No	Delete remote files/dirs not in source
Verbose	No	Show detailed progress

Exclusion Patterns

Pattern	Excludes
*.tmp	All .tmp files
node_modules	node_modules directory + contents
.git	.git directory + contents
bin	bin directory + contents
*.log	All .log files

Common examples:

# Development
-ExcludePatterns @("node_modules", ".git", "bin", "obj", "*.tmp", ".vs")

# General
-ExcludePatterns @("Temp", "Cache", "*.tmp", "*.bak", "Thumbs.db")

Automated Backups

Create C:\Scripts\DailyBackup.ps1:

$logFile = "C:\Logs\backup-$(Get-Date -Format 'yyyyMMdd-HHmmss').log"
Start-Transcript -Path $logFile

try {
    Import-Module BackupWindowsToLinux

    Sync-ToLinux `
        -Source "C:\Data" `
        -Destination "/backup/data" `
        -HostName "backup-server.local" `
        -UserName "backupuser" `
        -KeyFile "$env:USERPROFILE\.ssh\backup_key" `
        -Verbose

    Write-Host "Backup completed successfully" -ForegroundColor Green
}
catch {
    Write-Error "Backup failed: $_"
}
finally {
    Stop-Transcript
}

Schedule it:

$action = New-ScheduledTaskAction -Execute "powershell.exe" `
    -Argument "-ExecutionPolicy Bypass -File C:\Scripts\DailyBackup.ps1"
$trigger = New-ScheduledTaskTrigger -Daily -At 2am
Register-ScheduledTask -TaskName "Daily Linux Backup" -Action $action -Trigger $trigger

How It Works

1. Connects to remote via SSH
2. Scans local files recursively
3. Builds remote file index (path, size, timestamp)
4. Compares each file (size + timestamp with 2s tolerance)
5. Transfers only changed files via SCP
6. Preserves modification timestamps
7. Optionally deletes orphaned files/directories

Troubleshooting

"OpenSSH client not found"

Add-WindowsCapability -Online -Name OpenSSH.Client~~~~0.0.1.0

"SSH connection failed"

• Verify: ping 192.168.1.100
• Test SSH: ssh -i "keyfile" user@host
• Check firewall allows port 22

"Permission denied (publickey)"

# On Linux server:
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Files always transfer

• Check clock sync (both systems should use NTP)
• Verify filesystems preserve timestamps

Security Best Practices

1. Use SSH keys (never passwords for automated backups)
2. Protect private keys with passphrases
3. Use dedicated backup user with minimal permissions
4. Rotate SSH keys annually
5. Keep audit logs of backup operations
6. Restrict SSH access by IP in firewall

License

MIT — see LICENSE