If you have multiple Macs in your home, and you’re running OS X 10.5, you may run into a permissions problem with each user’s Drop Box. For those not familiar, the Drop Box folder (in your user’s Public folder) can be used to copy files and folders between machines and users without logging into the remote machine. When connected as a guest, you have rights to add files to—but not see the contents of—any user’s Drop Box. This makes the Drop Box a fast and easy way to move files from one machine to another, as you can do so without logging in.
If you receive something in your Drop Box, you should be able to access it like any other file in your user’s folder—you should be able to modify it or delete it, for instance. But some users have been having troubles with this—if they open a file that was placed in their Drop Box, it will open as Read Only, indicating they don’t have rights to make changes to that file. You are more likely to experience this problem on a machine that’s been migrated from 10.4, but I’ve also talked to someone who saw it on a brand-new iMac, so it’s not exclusive to those who upgraded to 10.5.
Why does this happen? It’s a long story, some of the details of which are beyond my comprehension, but it’s related to (in some cases) differences in 10.4 and 10.5’s handling of users and groups, and the fact that 10.5 uses access control lists (ACLs) to control how items placed in the Drop Box are handled. If you’re experiencing the problem, the likely cause is that your user is missing an ACL for the Drop Box. There are two fixes for this problem—a one-time fix, and a permanent fix.
The one-time fix is to simply copy—not move—the files out of the drop box. The act of copying (which you can do by Option-dragging) the files to a new location also gives your user full ownership of those files. But it’s annoying (and time-consuming, if the files are large) having to do this every time someone gives you a file or folder. If you receive a lot of files via your Drop Box, consider the permanent fix instead.
The permanent fix to this problem is to add the proper ACL to the Drop Box folder. To do that, open Terminal, and enter this command—note that you can’t just copy and paste it as is, as you need to replace the two occurrences of short_username with your user’s actual short username. For that reason, I suggest copying this into TextEdit, editing it as needed, and then pasting it into Terminal.
chmod +a "short_username allow list,add_file,search,delete,add_subdirectory,delete_child,readattr,writeattr,readextattr,writeextattr,readsecurity,writesecurity,chown,file_inherit,directory_inherit" /Users/short_username/Public/Drop Box
After running this command, you should find that your Drop Box works as expected, and you have full rights to files that others leave for your use. Please note that I haven’t experienced this issue myself, so I haven’t personally tested this solution. However, fellow Macworld author Kirk McElhearn did have this problem, and he reports that the ACL method shown here did, in fact, solve the problem.