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Columns & Editorials

by Kyle D'Addario
& Wincent Colaiuta

Filesharing In Mac OS X
April 13th, 2001

Last week Kyle provided some tips on using Mac OS X's inbuilt webserving capabilities. In this column I talk about another important way of sharing your data with other users in Mac OS X: Apple's filesharing system.

The Mac OS has long been able to share files across a network via the AppleTalk protocol and over LocalTalk (Macintosh serial) connections. With Mac OS 9, users were first able to share files over TCP/IP connections – the dominant standard on the Internet – within their local networks and even across the globe. This capability existed straight out of the box and no additional software (such as AppleShareIP, for instance) was required.

Mac OS X maintains this functionality with the ability to share files over the Internet built in to the OS as standard. What this means is that, "under the hood", each and every copy of Mac OS X supports AFP (Apple File Protocol) over TCP/IP as both client and server.

On the surface, however, things couldn't get much simpler. To enable file sharing under Mac OS X you just proceed to your Applications folder and:

  1. Launch the "System Preferences" application.
  2. Click the "Sharing" icon.
  3. At the very top of the Sharing pane you'll see, "File Sharing Off", the default setting for Mac OS X. Starting file sharing is as easy as clicking the "Start" button.

File sharing usually starts up quite quickly. On my year 2000 PowerBook it takes about 10 seconds. Once the process is finished the Sharing pane updates to show "File Sharing On" and is easily toggled back off with a click on the "Stop" button.

So what exactly is being shared?

When you activate File sharing you are actually sharing the contents of the "Public" folder inside your home directory. If you navigate to your home directory, select the "Public" folder, press command-I (to display the "Show Info" inspector) and then choose "Privileges" from the popup menu, you will see that everybody is granted read-only access to the "Public" folder by default. You as owner may write to that folder, but nobody else can.

Inside the "Public" folder is a folder called "Drop Box". If you examine the privileges for the Drop Box you'll see that in this case anybody can write to the folder but not read from it. This is useful for those times when people might want to pass on a confidential file; they want to write it to your Drop Box, but they don't want anybody but you to be able to read it.

One thing to note, however, is that under Mac OS X guest access is granted to your Public and Drop Box folders by default. This means that anybody connected to your network can access those folders without a username or password. If you're on the Internet (and not safely hidden behind a firewall) then anybody who knows your IP address can view the contents of your Public folder, and write files to your Drop Box. If this concerns you, then I suggest you change the Privileges for those folders to something more secure; use the Show Info window to make it so that "Everybody else" has a privilege setting of "None". (Thanks to Gino Cerullo for sending in this tip.)

So that's serving your files to other machines on the network. How do you access the files on other machines? It's a simple matter of using the Finder's "Go" menu and selecting "Connect to Server…". At the very least you'll see your own computer listed in the dialog (under "Local Network"). If there are other machines with filesharing turned on then you'll see them listed too.

Try clicking on your machine name. In my case the address field changes to show "afp://". Obviously, if I wanted to connect to a friend's Macintosh over the other side of the Internet, this is the place where I could enter the right address (as either an IP number or a human-readable hostname).

When you choose a machine and click "Connect" you are shown a dialog that will be familiar to users of Mac OS 9's file sharing features (see below). You can connect as a guest, or as a registered user, the latter option requiring a valid username and password.

After clicking "Connect", simply select the volumes you wish to mount (these "volumes" will correspond to users on the machine to which you are connecting). The volume appears on the desktop like a normal disk icon, and can be put away when you're done by dragging it onto the trash.

It's worth noting that when you connect to a home directory using the username and password associated with that home directory, you're given access to the entire home directory, not just the "Public" folder. Connecting as a guest, however, means you only get access to the "Public" section.


At this point we've just scratched the surface of the File Sharing capabilities of Mac OS X. Unlike Mac OS 9, Apple's new operating system does not have a "File Sharing" control panel, nor a "Users and Groups" control panel to control the access to folders and files on a per-user basis. In order to do that in Mac OS X you'll have to use the very powerful "NetInfo Manager" application (in the "Utilities" folder, inside the "Applications" folder). I won't steal Kyle's thunder by telling you what he's planning to write for next week's Hot Cocoa column, but I can reveal that my own column the week after will be on using the User and Group management features of NetInfo Manager and particularly, how to use it to give specific users specific access to folders on your hard drive. Until then good luck!


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You are encouraged to send Richard your comments, or to post them below.

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Kyle D'Addario is the assistant editor of The Mac Observer and has logged about as much time on Mac OS X as is humanly possible. Kyle studies Computer-Mediated Communication, whatever that is, at the graduate level, and was a founding member of the original Webintosh team.

Wincent Colaiuta runs Macintosh news and criticism site,, and joined The Mac Observer team as a contributor in March 2001. He has worked with computers since 1984, and his interests in that area include Macs, PHP programming and security.

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