Moving a folder with “sudo mv”, how to preserve ACLs?

Question

I'm moving a whole folder from one volume to another (both HFS+), using sudo mv, and thought ACLs would be preserved. However at the end of transfer I see that they haven't been kept, and since mv deleted the files in the original volume I can't restore them.

Why did this happen, and how to do it right next time?

Answer 1

mv uses cp when moving files between different volumes, and it looks like the -p option isn't used, so ACL aren't preserved.

However if moved in the same volume ACLs are of course preserved.

Answer 2

It would be better to use the ditto command since it is aware of resource forks, HFS attributes as well as ACL. You can alias it or just rewitpre your brain to use ditto as best fits your workflow.

Answer 3

I'm quite suprised to read that ACLs weren't preserved. Do you have GNU mv installed and set to take precedence over /bin/mv?

According to the man page for mv (on both 10.5.8 and 10.8.2) cp -p is used when moving files across a filesystem boundary:

As the rename(2) call does not work across file systems, mv uses cp(1) and rm(1) to accomplish the move. The effect is equivalent to:

rm -f destination_path && cp-pRPsource_file destination && rm -rf source_file

cp -p preserves ACLs:

-p Cause cp to preserve the following attributes of each source file

in the copy: modification time, access time, file flags, file mode, user ID, and group ID, as allowed by permissions. Access Control Lists (ACLs) and Extended Attributes (EAs), including resource forks, will also be preserved.

I moved a file to a flash drive and back with mv and ACLs were preserved (tested on my old PowerBook running Mac OS X 10.5.8 "Leopard" and with OS X 10.8.2 "Mountain Lion").

If both filesystems were HFS+ formatted, as you state, and there is no GNU mv around, I have to conclude that you are using some (very) old Mac OS X version. In that case either use the Finder, cp/rm or, as explained in bmike's answer above, ditto.