You're sat in the lounge with your family, and you want to show them your holiday videos on the Mac mini you use as a media centre. But the videos are on your iMac. How do you transfer them?
Or maybe you've just finished a Keynote presentation, and need to share it with a colleague who has his own user account on your Mac. It's too big to email, so how do you get it to him?
Article continues below
You could use a USB stick, or email smaller files to yourself. Or for your home network, you could invest in a network attached storage (NAS) drive, accessible to everyone. But there's another way.
Using OS X's file-sharing abilities, you can define a folder as 'shared', enabling other computers on your network - and other user accounts on your Mac - to access them. Privileges can be set to give different access rights to different accounts, allowing people or groups to read, write or both.
Every OS X user account has a Public folder, which is used to share files with other people. It's always accessible to other user accounts on the same machine, and if File Sharing is enabled, it can be used to share files over a network too.
Your Public folder is found in Hard Drive/Users/[username]. Inside is another folder called Drop Box. By default, anyone connected to your Mac can read from (and copy files from) your Public folder, and write to (but not open) the Drop Box, though this can be configured if you wish. File Sharing also lets you define other folders as publicly accessible.
To activate and configure your Mac's File Sharing function, you must be logged on as an administrator, or at least know an administrator's username and password. Under the Apple menu, choose System Preferences. Open the Sharing pane - the one that looks like a folder with a figure in a yellow diamond on it.
If you're logged into an account that doesn't have administrator privileges, click on the lock in the bottom-left corner of the window, and enter the name and password of an administrator. If you're using an admin account, it should already be open.
Click on the check box labelled File Sharing to enable this feature. Your public folder is now accessible to other users on the network, and can be accessed by clicking on your computer in the Shared column in a Finder window's side bar (if the side bar is missing, toggle it on or off by pressing the pill-shaped button in the top-right corner).
You can now make files accessible to others by moving or copying them to your Public folder, and they can give files to you by putting them in your Drop Box folder, which everyone can see, but only you can open.
Once again, these are default settings, and can be configured to behave differently, as we'll cover in more depth later. But what if you want to share other folders?
For example, to give everyone in your house access to your Movies folder, without moving it into your Public folder? To do this, we must define Movies (or indeed any folder) as 'shared'. With File Sharing highlighted, two panels appear to the right, one titled Shared Folders and one called Users. Both have little boxes underneath labelled '+' and '-'.
To share a folder with everyone on your network, press the '+' button under the Shared Folders panel and navigate to the folder to share. To remove a folder from this list, highlight it and press the '-' button.
The Users panel
The Users panel allows you to set privileges for individuals and groups. In the Shared Folders panel, select the folder you wish to affect. The Users panel shows the access rights currently enjoyed by yourself and others.
By pressing the '+' button under the panel, you can add individual users and groups. Again, highlight and press '-' to remove them.
New user or group accounts can be created in the Accounts system preference, or you can set up a new user without creating a new account on your Mac by pressing the New Person button in the dialog window that appears when you press '+'. A password can also be set for this new person.
To add him or her to the Users panel, highlight his or her new account and press Select. By default, a new user or group added to the Users list has Read Only access. To change this, click on the words Read Only and select another option from the pull-down.
Read Only access means that a person or group can open that folder and take files, but cannot put anything in it or edit files that are already there. Write Only access is the exact opposite - the user can copy files into that folder for the account holder to use, but cannot open it or take anything from it. A person or group with Read & Write privileges has full access to that folder, and can open, edit or take files, copy data to the folder or delete items.
The group titled Everyone is a global setting, and can also be set to the self-explanatory No Access. Note that if a user account is set up for someone who's also a member of a group, personal settings override group restrictions.
For example, if Fred Smith is given Read & Write access, but he's included in a group that has Write Only privileges, Fred can Read & Write.
An alternative way of creating and managing shared folders exists, apart from System Preferences. In Finder, highlight the folder you want to share, and press Command+i or right-click and select Get Info. This brings up that folder's Info window. At the foot of the General section is a check box entitled Shared Folder. Checking this makes it shared (if you check it with File Sharing off, you're invited to activate this feature).
At the foot of the Info window, in a section labelled Sharing & Permissions, you can set read and write privileges. If you want to share with computers running Windows or Linux, you have to activate the necessary network protocols to allow your Mac to communicate with the operating system that needs to access your files.
In the Sharing preference pane, click on Options. Apple Filing Protocol (AFP) is active by default, and allows you to share with Macs. To share with Linux and Unix systems, check the File Transfer Protocol (FTP) box. You're given a server address for Linux/Unix users to access, or they can browse for your computer by name. To share with Windows users, check the Server Message Block (SMB) box.
Check the user accounts you wish to enable for SMB, and enter the password for that account. When you're ready, click Done to finish.
Of course, MobileMe subscribers have another option. MobileMe's iDisk feature gives you 20GB of cloud storage, and a couple of easy ways to share your files with others. By uploading a file to your iDisk's Public folder, it can be downloaded by anyone.
To upload a file to iDisk through Finder, select iDisk from a Finder window's side bar or click on Finder's Go pull-down menu, scroll down to iDisk and select My iDisk. If you're not already logged on in System Preferences, you have to enter your details when prompted. You can then transfer files to any of your iDisk folders (including Public) through the Finder.
Alternatively, upload from the MobileMe website. Go to www.me.com and log in to your account. Click on the cloud icon in the top-left corner, and switch to iDisk. Select the folder you wish to upload to, and press the up arrow in the blue bar at the top of the website.
Now, navigate to the file you want to upload. If you want to password-protect your iDisk's Public folder, in the iDisk section of www.me.com, click the cog icon in the top bar and select Preferences; here you can opt to set, change or remove a password. You can also edit permissions to write to or delete files from the Public folder.
To access another user's Public folder from your own Mac, in Finder's Go menu, select iDisk > Another User's Public Folder. Enter the MobileMe account name of the person whose Public folder you wish to access, and the password if necessary. You can now download files from that person's folder, and also upload and delete files, if they've enabled this in their iDisk preferences.
Note that your iDisk's Public folder is stored on a cloud server as part of your MobileMe account's alloted storage space, and is not the same as your OS X account's Public folder.
If you want to give someone access to a specific file on your iDisk without putting it into the Public folder, you can invite them to download it by email. Log onto www.me.com/idisk, and navigate to the file you wish to share. Click on it, and then click on the Share File button in the right-hand column.
You're then given a URL at which the file can be downloaded. Enter the email address of the person you want to share it with and a message in the fields provided, and press Share; the URL is emailed, and the recipient can download the file just by clicking on the link. If you want to send the email from an account other than your me.com address, you can copy and paste the URL and leave the email and message fields blank. You still have to click on Share, though, or the file won't be shared and the link won't work.
Finally, MobileMe service Back to My Mac is an easy and convenient way of remotely accessing another Mac that's logged into the same account, from both your home network and over the internet. It's a great way of using your notebook to retrieve files from your home machine while out and about, but it must be switched on if you're to do it.
How to activate and use OS X File Sharing
1. System Preferences
Open System Preferences from the Apple menu, and go into the Sharing preference pane, found in the Internet & Wireless section. It looks like a folder badged with a stick man on a yellow diamond. It's here that you activate File Sharing, and other sharing services.
2. Switch File Sharing on
Click the File Sharing check box to turn on File Sharing. You'll need to be an administrator, or know an admin's name and password. File Sharing is switched on, and a list of currently shared folders appears in the central panel. Each user account has its own shared Public folder.
3. Add folder to share
To define another folder as shared, click the '+' button under the Shared Folders panel. Navigate to the folder you wish to share (such as Movies, as shown here) and click on Add. It appears in the Shared Folders panel. If you want to unshare a folder, highlight it and click '-'.
4. Add users
You can add new users in the Users panel. Highlight the shared folder you wish to give access to, and click the '+' button under the panel. Choose a user or group that's already set up in the Accounts pane, or click New Person.
5. Access Privileges
Modify a user's access privileges via the pull-downs in the second column of the Users panel. Read & Write gives full access to a folder, Read Only lets them take files but not put any in, and Write Only lets them copy to, not from it.
6. Use the Info Window
Most of these functions can be accessed via a folder's Info window. Highlight the folder in question, press Command-i, or right-click and select Get Info. From this window, you can share and unshare the folder and modify permissions.