Running Disk Defragmenter from a Command Line

The command-line version of Disk Defragmenter allows you to exercise fine-grained control over the defragmentation process and uses the exact same program code as the scheduled version. To use this command for a specific drive, type defrag d: in an elevated Command Prompt window, where d is the drive letter or mount point of an existing volume.To see the full range of the defrag utility's capabilities, type defrag /?.Among the more useful switches are the following:

• -c Defragments all volumes on the computer; use this switch without specifying a specific drive letter or mount point.
• -a Analyzes the specified volume and displays a summary of the analysis report.
• -f Consolidates the free space on the specified volume, reducing the likelihood that large new files will be fragmented.
• /r Defragments multiple volumes in parallel. If your volumes are on physically separate disks, you might save a bit of time by using this switch.
• -v Displays complete (verbose) reports. When used in combination with -a, this switch displays only the analysis report. When used alone, it displays both the analysis and defragmentation reports.
• -w Performs a full defragmentation by consolidating all file fragments, regardless of size

In addition to the documented switches listed, the command-line Defrag utility includes this useful but undocumented switch:

• -b The -b switch optimizes boot files and applications while leaving the rest of the drive undisturbed.