What are "Paste Item Exactly" and "Duplicate Exactly" in Finder?

When duplicating or pasting a file, the new file isn't exactly like the original. While it has the same contents, modification date, permissions, and extended attributes, it lacks the original's ownership information: You are the owner of the file you create!

Especially when changing system-wide configuration files, or doing administrative tasks using other users' files, it's important to mind the permissions, otherwise some services refuse to work, or the other user accounts might no longer be able to access or edit the files.

Duplicate Exactly and Paste Item Exactly preserves the original's basic ownership information (user and group). This isn't usually possible, and require administrative permissions to perform. It's an easy way to make temporary backups with correct original permissions before replacing system files.

Access control lists aren't preserved though, even when using the … Exactly commands.