Understanding AutoCAD backup and autosave files
Issue:
You want to know more about the backup (. bak) and autosave (. sv$) files that AutoCAD creates, where they are located, and how to use them.
Solution:
• Backup (bak) Files
• Automatic Save (sv$) Files
• Temporary (ac$) Files
• Drawing Recovery Manager
Backup (.bak) Files
Drawing backup files are typically created every time that you manually save a .dwg file. By default the file will be saved in the same location as the .dwg and will have the same name as the drawing but with a .bak extension, such as, site_topo.bak. A backup file is an exact copy of the drawing file prior to the last save. As such, backup files are always one version older than the currently saved drawing. Only one backup file is retained at a time so newly created backups will always replace older backups of the same name.
Note: Backup files are created only if the system variable ISAVEBACK is set to 1.
Backup files are essentially renamed .dwg files. You can recover data saved in .bak files by renaming the .bak extension to dwg and then opening that file in AutoCAD.
MOVEBAK Command
Included in the AutoCAD Express Tools is the MOVEBAK command which allows you to specify an alternative folder for your bak files when created. If you want to keep all your bak files in a single location—as opposed to keeping them in the same folder as the associated drawings—you can use MOVEBAK to specify another folder and all bak files will be automatically moved there when created. Enter "." as a value to reset AutoCAD to the default behavior.