Quick and Easy File Backup Using PowerShell and DotNetZip

Backup your files easily, using PowerShell and DotNetZip, from the command line.

Backing Up

There is no shortage of file backup utilities, so there is no excuse not to back up your files. However, over the course of a typical workday, many of us create and edit files on our own computer, as well as files on multiple networked computers. Although these networked computers usually have their own backup processes, restoring lost files from them often requires contacting Support, filling out paperwork, and waiting, and waiting, and…

As a result, I prefer to create my own backup of important files I am working with on networked computers, using a simple PowerShell script. I call the PowerShell script from the command line on an ad-hoc basis, and nightly using a scheduled task. When creating the backup, to save space, the script compresses the files using the free DotNetZip Library, available on CodePlex. This is a popular library used by .NET and PowerShell developers. There are many code examples on the Internet. The script also appends the backup file’s name with a descriptive suffix and timestamp, making the backup file unique.

Using the Script

The script’s main function, Create-ZipBackup, takes three parameters:

1. $target – Target directory or file to be backed up (i.e. ‘\\RemoteServer\ShareName\MyProject’)
2. $destination – Destination directory for backup file (i.e. ‘c:\My Backups’)
3. $fileNameSuffix – File suffix used to name the backup file (i.e. ‘ProjectPlan’ – ‘ProjectPlan.BU.20120908_070913.zip’)

Here is an example of calling the script from the command line, using the above example parameters. To save time when calling the script multiple times, I’ve placed the path to the script into a temporary variable:

SET script=C:\Users\gstaffor\Documents\PowerShell\BackupAndZip.ps1
powershell -command "& { . %script%; Create-ZipBackup -target '\\RemoteServer\ShareName\MyProject' -destination 'c:\My Backups' -fileNameSuffix 'ProjectPlan'}"

Alternately, to call the Create-ZipBackup function from within the script directly, you would use the following PowerShell command:

Create-ZipBackup -target '\\RemoteServer\ShareName\MyProject' -destination 'c:\My Backups' -fileNameSuffix 'ProjectPlan'}"

The Script

################################################
#                                              #
# Compress and backup files using DotNetZip    #
#                                              #
# Gary A. Stafford - rev. 09/08/2012           #
# www.programmaticponderings.com               #
#                                              #
################################################

# Enforce coding rules in expressions & scripts
Set-StrictMode -version 2.0

# Location of Ionic.Zip.dll
[Void] [System.Reflection.Assembly]::LoadFrom(
    "C:\Ionic.Zip.dll")

function Create-ZipBackup
{
    param (
        $target,
        $destination,
        $fileNameSuffix
    )
    
    [string] $date = Get-Date -format yyyyMMdd_HHmmss
    [string] $fileName = "{0}\$fileNameSuffix.BU.{1}.zip" -f $destination, $date
    [IO.FileInfo] $outputFile = [IO.FileInfo] $fileName
    [Ionic.Zip.ZipFile] $zipfile = new-object Ionic.Zip.ZipFile

    [Ionic.Zip.SelfExtractorSaveOptions] $selfExtractOptions = 
        New-Object Ionic.Zip.SelfExtractorSaveOptions
    $selfExtractOptions.Flavor = [Ionic.Zip.SelfExtractorFlavor]::ConsoleApplication
    $selfExtractOptions.DefaultExtractDirectory = $outputFile.Directory.FullName
    $selfExtractOptions.RemoveUnpackedFilesAfterExecute = $false
     
    $zipfile.AddDirectory("$target")
    $zipfile.UseZip64WhenSaving = [Ionic.Zip.Zip64Option]::Always
    $zipfile.SaveSelfExtractor($outputFile.FullName, $selfExtractOptions)
    $zipfile.Dispose();
    
    If (!(Test-Path $fileName))
    {
        Write-Host ("ERROR: Backup file '{0}' not created!" -f $fileName)
        break
    }
    
    Write-Host ("SUCCESS: Backup file '{0}' created." -f $fileName)
}

Error Handling

Note, this basic script does not contain much in the way of error handling. There are a some common reasons the script can fail. For example, a file whose file path exceeds the maximum character length of 260 characters, will throw an error. Trying to back up files which you (logged on user account) does not have permissions to, will also throw an error. To catch these types of errors, you would need to add functionality to iterate recursively through all the target files first, before compressing.