In addition to building deployable packages of applications and other files, Composer allows you to build DMGs of preconfigured operating systems. OS packages can save you time and enhance consistency across your network.

While building an OS package with Composer is similar to building one with the Disk Utility application, Composer allows you to clean up the OS by removing unnecessary files before building the DMG.

Composer allows you to manage the following cleanup options for an OS package:

Compress Disk Image
This option compresses the OS package DMG.

Delete Temp Files
This option ensures the files in /private/tmp are deleted before building an OS package. These files are usually deleted during the startup process.

Delete Virtual Memory Files
This option ensures that Virtual Memory files are deleted before building an OS package, including the potentially large sleepfile. These files are usually deleted and re-created during the startup process.

Delete Special Files
Apple recommends deleting the following files before building an OS package:

/private/var/db/BootCache.playlist /private/var/db/volinfo.database

This option ensures that these files are deleted.

Delete Caches
This option removes files in the /Library/Caches directory before building an OS package.

Remove System Keychain
This option removes the System keychain from the OS to ensure that a new System keychain is created. This can prevent the “This computer already exists” error when binding a computer to a directory service.

Ensure Trashes are Empty
This option empties the Trash for any user with items in the ~/.Trash folder. It also updates a user’s com.apple.dock.plist file to reflect that the Trash is empty.

Delete MCX Records in the Local Directory Service
This option removes the /var/db/dslocal/nodes/Default/computers/localhost.plist file before building an OS package.