Share Group Folders

Aside from the files an OS X Server shares across your entire enterprise, there's often the desire within individual workgroups to have private storage areas for their own projects. These group folders are essential for departments like HR and Accounting, but they can also be helpful for less security-conscious groups as a staging area before sharing their final work company-wide. Fortunately, while the process of creating these file shares isn't obvious, it also isn't complicated.

First, select a group from your Open Directory domain in the "Accounts" pane of Workgroup Manager. Then click the "Group Folders" button, and select a share point under which you'd like the group folders to appear. By default, Mac OS X uses /Groups, which comes pre-configured as a share on a new installation. Next, you'll need to choose an owner for your new folder. Your directory administrator account makes the most sense here, as you'll be using the group (not owner) attribute to determine access permissions. With these options configured, hit "Save".

For whatever reason, you can't actually use Workgroup Manager to create the folder you've just configured (as you can with user's home directories). Instead, you'll need to open the Terminal and type:

sudo CreateGroupFolder

This will build a folder for every group assigned a share point, not just the most recent, so if you're deploying multiple group folders it makes sense to run this command after they've all been set up in Workgroup Manager. This also sets the permissions for each group folder as read-only to the group itself, and only read-write to the individual user defined as it's owner. To remedy this in the Terminal, type the following, replacing PATH-TO-FOLDER with the full Unix path to each group folder:

cd PATH-TO-FOLDER
sudo chmod 770 Documents/ Library/

This will allow access by workgroups to their own group folders with a simple permissions scheme. For more complex sharing setups, you may wish to add an access control list as well, in the sharing pane of Server Admin.

Finally, if you're utilizing managed preferences in an Open Directory environment, you can set group folders to automatically mount when a member of that group logs in to their workstation. Moving to the "Preferences" pane of Workgroup Manager, click the "Login" icon, then the Items button on the far right. Check "Mount share point with user's name and password" and "Add group share point", then click "Apply Now".

Not only can each workgroup have their own private file share, but users will connect to those shares automatically when logging in to their Open Directory account.

Portable Home Directories — Part 2

Last week, in part one of this series, we took began deploying Portable Home Directories, reviewing their prerequisites and enabling the mobile managed preferences. This week we'll continue the process, by setting up an AFP share to host our user homes and configuring our Open Directory accounts to take advantage of them.

Sharing Portable Home Directory Files:

In order to make your server-based home directories available to other machines, you'll need to share them out to your network (preferably via AFP). In Leopard, the "File Sharing" settings reside in the Server Admin application. Open it, then select your server name, and choose the gear-shaped "Settings" button from the toolbar. You'll see a collection of potential server features to enable (such as allowing SSH and ARD access) including a listing for "Server Side File Tracking". Checking the box and clicking "Save" will allow Mac OS X server to cache file changes prior to synchronizing home directories, which offers a significant performance boost over Tiger's system of scanning and comparing home directory contents.

Next, select "File Sharing" from the Server Admin toolbar (or the equivalent settings in Tiger's Workgroup Manager). If your server has fast redundant disk space available to hold your portable home directories, there's not a compelling reason to not just share out /Users. If you have a large number of users (or a small boot disk), you'll want to create a separate share on external storage. In either case, select the "Volumes" and "Browse" buttons below the toolbar and select the folder you'll be using for your Portable Home Directories, then click the "Share" button right above the file browser and "Save" at the window's bottom-right.

Once you share the directory, a new "Share Point" button will appear at the center of the "Sharing" pane. Select it, then check "Enable Automount". You'll then be asked to enter an administrative user name and password for your Open Directory domain. Keep the default setting of mounting user home folders over AFP by clicking "OK", then move on to the "Protocol Options" button below it.

When Portable Home Directory deployments go wrong, it's usually at this stage. In the AFP "Protocol Options", be sure that "Allow AFP guest access" is checked (you'll also want to uncheck the options to share via SMB, FTP, or NFS). If you have other AFP shares active (which you most likely do), be sure guest access is turned off on the rest of them. Then select "AFP" from the service list on the left of the Server Admin window, choose the "Access" pane, and check "Enable Guest access" there as well.

This may seem counterintuitive, as guest (or unauthenticated) access to the home directory share may sound like a terrible idea. In most cases you wouldn't want any data shared out to network guests, and Apple even forces you to confirm the setting in two separate places. In the case of Portable Home Directories, however, the shared volume gets automounted prior to any user logging in. The data inside each home directory stays private, but the root of the share needs to be accessible to any machine bound to the Open Directory domain. Guest access is the mechanism through which this is achieved, and without it the remainder of your deployment process won't get anywhere.

Assigning Portable Home Directories To User Accounts:

Now that your mobility preferences are set and your AFP share is set to automount, the final step is assign home directories to your existing users. Open Workgroup Manager and select "Accounts" from the toolbar, then highlight a test user from the left column and choose the "Home" pane. By default, two options are offered as home directory locations, /Users and None. Instead, click the "plus" button at the bottom of the list to add an additional option.

In the dialog sheet that appears, use the first field to enter the AFP address of the home directory share in URL format (such as afp://server.example.com/Users). In the second field, fill in just the name of the user's home directory, which should be the same as their account "short name". In the third field, enter the full path of the automounted home share as it will appear on client machines. This begins with /Network/Servers/, then the address from the first field minus the afp:// prefix, and finally the user's short name. When all three fields are filled properly, click "OK", then assign the user a disk quota (somewhere between 20-40GB is reasonable for most user environments) and hit "Save".

With this first account done, you can now highlight all the users who'll be getting mobile accounts, select your pre-configured share point, assign a quota, and save those settings to the entire list at once. If these are new accounts, you can even use the "Create Home Now" button to populate your AFP share with custom home directories. If you'll be syncing existing home directories on client machines, you don't have to create a home folder at all, instead allowing the data to copy to the server on their next network-based login.

Recommended Reading: For the full story on Portable Home Directory setup, try the essential Leopard User Management Guide [PDF - 2.5MB] at Apple.com.

Portable Home Directories — Part 1

Available since version 10.4, Portable Home Directories have become one of the most elegant and well-implemented features of a full Mac OS X Server deployment. Functioning much like Windows' roaming profiles (or earlier Solaris NFS/NIS environments), they allow a user to log in from any computer on your network while retaining their personal data and settings. Unlike entirely network-based systems, however, they do so by synchronizing user data to the server (so that a full copy of the home directory exists in both locations), eliminating the need for constant connectivity.

Portable Home Directories make for simpler backup of user data, both by copying off the server rather than each client machine, and by allowing remote users to synchronize via VPN. They also free users from being tied to a single machine, allowing for greater flexibility and less service down-time. It's because this functionality is so powerful that it's often assumed to be difficult to put into practice. Instead, with the proper infrastructure already in place, deploying Portable Home Directories is practically the reward for having done everything else right.

Planning For Portable Home Directories:

Before you actually implement any kind of server-based account storage, you'll want to make sure you have sufficient storage and bandwidth on an available OS X server. This may seem obvious to some, but for reasonable performance, fifty users with a 40GB quota requires at least 2TB of relatively high-speed (and hopefully redundant) disk attached to a gigabit network switch. This isn't an exotic setup by any means, but it may be more than you just have lying around.

You'll also need clients bound to a functioning Open Directory environment, complete with internal DNS. If you don't yet have this set up, refer to our earlier series on how to master Open Directory. Once Directory Service users and groups are in place, Portable Home Directories are nothing more than cleverly deployed managed account preferences. There's a lot to keep track of, but very little you wouldn't already know how to do.

Configuring Portable Home Directory Preferences:

In Workgroup Manager, browse to the "LDAPv3" directory (as opposed to the local user directory), then choose the multi-headed "Groups" button on the left and the "Preferences" icon from the toolbar. Select the group (or groups) you're offering Portable Home Directories, then click the "Mobility" icon in the center of the window to configure that group's settings. If you're deploying this feature to all your users, you're better off creating an all-encompassing "Employees" group to do so.

Beginning in the "Account Creation" tab with the "Creation" pane, choose to manage these Preferences "Always", the check "Create mobile account when user logs in to network account". Uncheck the box which requires confirmation, as this allows the user to skip the Portable Home Directory set up for their individual account. Below that, choose to "Create home" directories "with default sync settings".

Next comes the Account Expiry tab, new to 10.5. By allowing you to set a time limit after which the client-side copy of a home directory expires, it helps clean up the occasional "orphaned" set of user data (a full home directory left, for instance, on a machine only used once by that user during maintenance on their own machine. This feature can reduce the chance of accidentally filling client machines with multiple unused accounts, but does so at the risk of letting the computer determine when data should be disposed of. If you enable it, do so with caution.

Finally, the "Rules" tab lets you set what data will synchronize and when. Start with the "Login & Logout Sync" pane and once again click the button to "Always" manage, then check the box to "Sync at login and logout". The first list above allows you to set which directories you'll sync, and unless you feel you can fully predict your users' behavior the best approach is usually to select the entire home directory (as represented by the tilde symbol). You can then choose what not to sync in the second list below, including full paths, partial names, and even regular expressions. Be careful if you delete any of Apple's pre-configured items to skip, especially ~/Library/Application Support/SyncServices, which can result in synchronization issues and potentially data loss. The "Merge with user's settings" box allows you to decide if individuals can add or subtract to the list of data being synchronized.

The Background Sync pane, functions identically, and in most cases makes sense to configure identically as well. The only exceptions would be huge local files which change often, or live databases which won't sync properly. The Entourage database, for instance, sits both criteria and should be excluded from background synchronization. The "Options" pane also allows you to choose how often background sync takes place. With your configuration decided, click the "Apply Now" button to save your settings.

Next week, in part two, we'll set up the AFP share where your new Portable Home Directories reside and configure your Open Directory accounts to store user data there.

Recommended Reading: While I might not recommend implementing it in a production environment, Greg Neagle's multi-part article on Portable Home Directory Without Open Directory provides fantastic under-the-hood information on exactly how Portable Home Directories function at his "Managing OS X" blog.

Restart Kerberos Manually

The Kerberos authentication protocol is an encrypted ticketing system at the heart of Apple's Open Directory. It is the basis for Mac OS X's "Single Sign On" features, and a required component for integration with Windows Active Directory domains. Unfortunately, it's possible for the Kerberos service to stop functioning properly, and when it dies, a good number of your network services die with it.

Ideally, you can simply click the "Kerberize" button in the "General" pane of Server Admin's Open Directory settings. That should restart the service. This article for when you find yourself in less than ideal circumstances.

Why Kerberos Can Stop On OS X Server:

When the Kerberos service fails, the likely culprit is a DNS issue. This isn't the only reason Kerberos can break, but it's most common and the easiest to test for. The Kerberos KDC service (or Key Distribution Center), requires matching forward and reverse DNS lookups, and changing a server's hostname or IP manually (or losing connection to your DNS servers) can require the machine to be re-Kerberized. Since Tiger, Mac OS X has also been designed to dynamically set a machine's hostname on boot using a reverse lookup, meaning that external changes to a server's DNS listings can cause it to change names and break its original Kerberos realm.

Before you try to restart Kerberos, you'll want to know which (if any) of these things went wrong. If you aren't sure how to go about this, check with whomever in your organization controls Domain Name Service, or use the procedure from the beginning of our article on setting up Open Directory.

How To Start Kerberos From The Command Line:

Once your server is properly registered in DNS, you can begin reconstructing your Kerberos realm. The first step is to create a new edu.mit.Kerberos file, which Mac OS X can fortunately do (somewhat) automatically. Open the Terminal and type:

sudo kerberosautoconfig -r REALM -m HOSTNAME

For this command, HOSTNAME is the fully qualified domain name of your server, such as server.example.com. REALM is the server's DNS name again, but this time in all capital letters, like SERVER.EXAMPLE.COM. Next you'll create a KDC database for the new Kerberos realm:

kdcsetup -f /LDAPv3/127.0.0.1 -w -a DIRADMIN -p PASSWORD REALM

Here DIRADMIN is the name of any user with directory administration privileges, and PASSWORD is their actual login password. Once that's done, you can Kerberize the server's Open Directory domain with the following:

sudo slapconfig -kerberize -f DIRADMIN REALM

Finally, configure the Single Sign On mechanism to utilize Kerberos authentication for all applicable OS X services.

sudo sso_util configure -r REALM -a DIRADMIN -p PASSWORD all

This should once again leave you with a fully-functioning Kerberos installation on your Open Directory server, all without ever having had to reboot the machine.

If you're following this procedure, keep one additional things in mind: Because the kdcsetup and sso_util commands unfortunately requires that you provide a password on the command line (and therefore store that password in your command history), it's good security practice to change that user's password immediately after this process.

Recommended Reading: For an illustrated overview of the Kerberos authentication Process, there's the handy Kerberos Chart [PDF - 72KB] at Computer World. For more depth into how Kerberos works on OS X, there's an excellent three-part article at AFP548.com.

Master Open Directory — Part 2

If you've got a Macintosh server in your environment, chances are it was originally purchased as a file server. With a few local accounts and enough disk space, a centralized environment to share common documents can completely change the way a small department functions. As the needs of your workgroup and your network grow, however, you're likely looking towards collaboration, scheduling, and security features. That's when Open Directory becomes an important part of network management.

In part one of this article, we explored the basics of getting Open Directory up and running. This week, we'll set security policy to restrict access to your network services, then create or migrate user accounts to the LDAP directory for distribution and set up your workstations to use them.

Secure Open Directory Access:

By default, Open Directory will allow access to any machine on the network. This may work fine in an isolated academic environment, but most businesses have greater security requirements imposed upon them. Those requirements are fulfilled by Kerberos, an encrypted ticket-based authentication system developed at an isolated academic environment called MIT.

Open the Server Admin tool and select the "Open Directory" option from your server listing on the left. Click the "Settings" button in the Toolbar, followed by the "Policy" button on the strip below it, and the "Binding" button on the strip below that. Check the top two boxes to require authenticated binding for directory services, then the next four to enforce the strict Kerberos protocols for authentication.

Now click the "Passwords" button to define your organization's minimum password requirements. An ideal policy varies widely depending on each individual environment, but keep in mind that overly strict policies often lead to weaker passwords overall (or complex passwords taped to monitors and under keyboards). Whatever you choose, be sure to check "be reset on first user login" password. This allows you to assign the same default password to all new and imported accounts, rather than assign each account a new password individually, then forces users to create a new one immediately.

Migrate Users To Open Directory:

Now that you can insure account information will be communicated securely, the next step Launch Workgroup Manager and log in under the directory administration account created in part one (diradmin by default) with the fully qualified domain name of your server (such as www.example.com).

This will open into the server's /Local/Default directory, where non-network account information is stored. If you already have local user accounts, you'll see them listed down the left column. Select those you're transferring to the Open Directory service, then select "Export..." from the "Server" menu. The dialog will prompt you for a name and location to save your exported account listing. This export file will contain all the users' existing account information except passwords, hence the importance of requiring new ones at login.

To move the accounts to Open Directory, click the tiny globe on the far left of the Workgroup Manager window, in the thin stripe just below the toolbar. Choose /LDAPv3/127.0.0.1, indicating that you're now editing the LDAP (lightweight directory access protocol) settings. You should see your directory administrator account to the left, but no other users listed. Select "Import..." from the "Server" menu, and you'll be presented with the dialog to re-import your accounts. If you're moving accounts to an empty directory, you can safely leave these options at their defaults and click the "Import" button. Your exported local accounts should now be listed down the left hand side as Open Directory accounts. Only once you're sure the new network accounts work properly should you then delete their local counterparts.

If you're setting up a brand new server, there are no accounts to move around. Instead, just select the /LDAPv3/127.0.0.1 directory, and create your new users and groups.

Bind Clients To Open Directory:

Now that you've made accounts visible to the network, you'll want to configure your other machines to utilize them. On your client machines, open Directory Utility, and click the plus sign at the bottom of the window. Leave "Open Directory" selected in the pulldown menu, then enter the fully qualified domain name of your Open Directory server and hit "OK".

The window will then expand to accept credentials for the authenticated binding you've required. Enter the username and password of your directory administration account, as well as a unique machine identifier (most often the hostname or serial number), then hit OK again. If the binding process is successful, you'll be greeted with a reassuring green light and a message that the Open Directory server "is responding normally".

If you're unsure if a computer bound properly, or has become unbound, the simplest test is to open the Terminal and type:

id diradmin

If you named your directory administrator account differently, just substitute that for diradmin, but be sure to use an account that exists only in the directory service and not on the local machine. The response should contain the UID, GID, and groups that user is a member of. Should the response instead be "no such user", and the user exists on the server, then the machine has become unbound.

Now that you can login to all your machines with Open Directory network accounts, you can leverage those accounts for OS X security, collaboration, and management features.