Robocopy

robocopy (Robust File Copy) is the built-in Windows tool for copying and mirroring folder trees, with retries, logging, multithreading and permission handling. Run it from cmd or PowerShell (PowerShell Cheat-Sheet). On Linux the equivalent is rsync; see Linux Basics.

Syntax: robocopy <SOURCE> <DEST> [FILES] [OPTIONS]. It copies the contents of the source folder into the destination folder.

Documentation: robocopy reference

Common Commands #

Copy vs Mirror #

/MIR is /E /PURGE. A wrong destination, or an empty or unavailable source, can wipe the destination. Always do a dry run first and double check the argument order:

robocopy C:\data E:\backup\data /MIR /L /NP /NJH /NJS   # preview only
robocopy C:\data E:\backup\data /MIR /R:2 /W:5 /XA:SH /LOG+:C:\Logs\mirror.log

A mirror is not a backup: deletions and corruption replicate too, so keep versioned backups as well. Never mirror onto the root of a drive unless you mean it: /MIR can delete protected System Volume Information content, so exclude it with /XD "System Volume Information" '$RECYCLE.BIN'.

Retries and Timing #

Always set /R and /W for unattended jobs, for example /R:3 /W:10.

What Gets Copied #

/COPY:<flags> picks the file info (default DAT): D data, A attributes, T timestamps, S NTFS security (ACLs), O owner, U auditing.

For a full file server migration with permissions: robocopy <SRC> <DST> /MIR /COPYALL /DCOPY:DAT /R:3 /W:5 /MT:16 /XJ /LOG:C:\Logs\migrate.log /TEE /NP.

Logging and Output #

Exit Codes #

The exit code is a bit field, so it is a sum. Codes 0 to 7 are success or partial success; 8 and above indicate failures.

Add them: 9 means files copied plus failures. In scripts treat -ge 8 as an error:

robocopy C:\src D:\dst /E /R:2 /W:5 /LOG:C:\Logs\job.log /NP
if ($LASTEXITCODE -ge 8) { Write-Error "Robocopy failed with code $LASTEXITCODE"; exit $LASTEXITCODE }
else { $global:LASTEXITCODE = 0 }   # reset so schedulers and CI do not see 1 to 7 as failure

In batch files use if %ERRORLEVEL% GEQ 8 (echo failed).

Scheduled Backup Example #

$roboArgs = '"D:\Data" "\\<NAS>\backup\Data" /MIR /R:3 /W:10 /MT:8 /XJ /NP /LOG+:"C:\Logs\backup.log"'
$action  = New-ScheduledTaskAction -Execute "robocopy.exe" -Argument $roboArgs
$trigger = New-ScheduledTaskTrigger -Daily -At 2am
Register-ScheduledTask -TaskName "NightlyRobocopy" -Action $action -Trigger $trigger -User "SYSTEM" -RunLevel Highest

Scheduled tasks are covered in PowerShell Cheat-Sheet.

Troubleshooting #

Alternatives #

Not Verified #

Options and exit codes were written from the Microsoft documentation and not executed. /COMPRESS needs recent Windows and SMB versions.