TweetFollow Us on Twitter

MacEnterprise: Screen Saver and loginwindow: Friends at Last

Volume Number: 26
Issue Number: 01
Column Tag: system administration

MacEnterprise: Screen Saver and loginwindow: Friends at Last

Using MCX to manage a new Snow Leopard feature

by Greg Neagle

Introduction

A couple of months ago, we looked at some of the new features in Snow Leopard. I noted that the screen saver now runs over the loginwindow - a feature I've asked for since 2001, when OS X was first released! But when I wrote that particular column, I had not yet discovered how to control the time before the screen saver activates, or how to specify which screen saver module runs. The answer, not surprisingly, is to use MCX - Apple's method for managing preferences. So this month, we'll look at controlling Snow Leopard's loginwindow screen saver, and along the way, talk about MCX in general. If you don't or can't use MCX in your environment, don't worry - we'll also look at a way to manage the loginwindow screen saver using the defaults command.

You may be asking yourself - why does anyone want a screen saver over the loginwindow? Even if they are worried about display "burn-in", why don't they just set the display to dim or the machine to sleep after a period of inactivity? Dimming the display or sleeping the machine might be good choices for some organizations. But in instructional labs, students gravitate towards machines that look "alive", and may assume a machine with a dark display is broken. In my environment, some of our machines are connected to color-calibrated CRT displays that must be kept "warm" to retain their calibration. Shutting down the machine or putting it to sleep causes the display to go cold and require time-consuming recalibration. In other organizations, there might be a desire to run a screen saver over the loginwindow that acts as an informational display. Also, many organizations want to leave their machines on and awake when no one is logged in so that administrative tasks can be performed in the off-hours. Whatever the reason you might need or want to run a screen saver over the Login Window, you finally have an Apple-supported method to do so. Prior to Snow Leopard, OS X administrators had to resort to all sorts of hacks and tricks to get Apple's screen saver or a pale third-party imitation to work over loginwindow.

MCX for everyone

If you aren't using MCX to manage your OS X machines, you really should be. If your machines are on Leopard or later, there's really no reason any longer not to; you don't need to have an Open Directory server; you don't need to extend your LDAPv3 or Active Directory schema. You can put your MCX management settings on the local computer using a technique referred to as Local MCX.

For more information on Local MCX, you can refer to past MacEnterprise columns in MacTech:

"MCX- No Excuses, Now!", MacTech, Volume 24, Issue 11, November 2008

http://www.mactech.com/articles/mactech/Vol.24/24.11/2411MacEnterprise-MCX-NoExcuses/index.html

"Loco for Local MCX", MacTech, Volume 25, Issue 2, February 2009

(available online in Feb, 2010)

Some additional Local MCX resources:

http://www.afp548.com/article.php?story=using-mcx-in-the-dslocal-domain

http://managingosx.wordpress.com/2008/02/07/mcx-dslocal-and-leopard/

http://www.macos.utah.edu/documentation/administration/local_mcx.html

http://homepage.mac.com/gregneagle/files/MW2009_IT803.pdf/P>

For the remainder of this column, I'll be using Local MCX to demonstrate the techniques, but they'll work with a traditional network directory-based MCX deployment as well.

Workgroup Manager

To configure the loginwindow screen saver using MCX, you'll want to use Workgroup Manager 10.6 or later. As of this writing, you can get the 10.6.2 version of the Server Administration Tools, which includes Workgroup Manager, at this URL:

http://support.apple.com/downloads/DL968/en_US/ServerAdminTools10.6.2.dmg

Open Workgroup Manager, connect to the directory service you are using (network or local), and select a Computer or Computer Group to manage. If you're following along and are trying this out, you might want to create a new computer group to experiment with; this allows you to experiment without affecting any existing computers or computer groups. When you are done experimenting, you can simply delete the computer group you created, and all your experimental detritus will be cleanly removed.

When managing the screen saver over the loginwindow, preference management must be done at the computer or computer group level. These preferences are not associated with individual users - in most cases, no user will be logged in when we're at the loginwindow, so user or group preferences would not be available.

For this column, I've created a Computer Group called loginwindowscreensaver, added my local test machine to the group, and then clicked on Preferences in the toolbar. The result is shown in Figure 1.


Figure 1 - Workgroup Manager preferences management

Click the Login preferences and select the Options tab, which should display a pane like that in Figure 2.


Figure 2 - Login preferences Options tab

At the bottom of the Options pane, you'll see the new options for managing the screen saver over loginwindow. You can set the idle time after which the screen saver starts, and specify which screen saver module runs. Make your choices, click Apply Now, and Done. That was easy! Any computers that are part of the computer group you are managing will now get these new preferences.

While this is a nice, easy-to-use interface for managing the loginwindow screen saver, in practice it can present a problem. If you use this pane, all of the settings in the pane are managed as a group. You may want to manage the loginwindow screen saver, but leave other loginwindow options alone; this interface doesn't really allow for that. If you use this interface, you cannot manage the screen saver at the loginwindow without also managing automatic login, Fast User Switching, external accounts and more. This may not be what you want. You might be looking for something a little more granular.

Editing Details

Fortunately, there is an alternate interface that gives you finer-grained control. If you refer back to Figure 1, you'll see that the Workgroup Manage preferences editor has two tabs: Overview and Details. The Login pane is available via the Overview tab. But we can get more precise control (and more options) by using the Details pane. If you are still in the Login preferences editor pane, click Done to return to the Overview, then click the Details tab. If you haven't imported any preference manifests yet, it will look something like Figure 3.


Figure 3 - Preference details

If you have previously imported some preference manifests, you will have additional entries, but that's not important right now. What we're interested in are the entries that have the gray circle with a white mouse pointer icon in the first column. These are the preferences we set as managed when using the Login pane under the Overview tab. We can now do some surgery so we are managing only the screen saver preferences.

If you examine the contents of com.apple.screensaver (as in Figure 4), you'll see that the loginWindowIdleTime and loginWindowModulePath are being managed, so you can just delete all of the other managed preferences; none of them will be managed.

Deleting .GlobalPreferences, com.apple.loginwindow, com.apple.MCX, and com.apple.systempreferences causes all of the preferences included in those domains to revert to being unmanaged. Now computers that are members of our loginwindowscreensaver group will receive managed preferences only for the com.apple.screensaver domain.


Figure 4 - com.apple.screensaver Managed Preferences

Once you've made these changes, if you go back to the Overview and look at the Login preferences you'll see all sorts of strange "half-checked" options, because the current settings no longer match anything that can be cleanly represented in the Overview interface. Once you start fine-tuning using the Details interface, you cannot use the Overview interface without erasing your detail work.

Preference Manifests

There is another way to work with Workgroup Manager, which is to use preference manifests. This method allows us to do all the work in the Details interface. If you're following along, and have taken my advice and are using a newly created computer group to test these settings, delete all of your managed preferences so you are working with a clean slate.

We'll start by adding in the new preference manifests for Snow Leopard, if you haven't already done so. In the Details preferences editor pane, click on the plus icon in the lower left. Navigate to /System/Library/CoreServices, select ManagedClient, and click Add.


Figure 5 - Imported preference manifests

You should see something similar to Figure 5. Adding ManagedClient.app imports a number of useful preference manifests, but the one we're interested in today is Screen Saver Loginwindow, or com.apple.screensaver, which should sound familiar.

Double-click Screen Saver Loginwindow. Select Always, and turn down the disclosure triangle. Click the New Key button. Click the new key's title - New Item - and select Login Window Idle Time from the pop-up menu. Click New Key again, and change the New Item to Login Window Screen Saver Module Path. The results should look like Figure 6.


Figure 6 - Screen Saver Loginwindow managed preferences

This is functionally identical to editing the "bare" com.apple.screensaver preferences, but if you use the Screen Saver Loginwindow preferences manifest, Apple gives you a little more information to work with. For the Login Window Screen Saver Module Path key, Apple has provided some info to let you know that not all screen savers will work over the loginwindow, so you must test. The Login Window Idle Time help text lets you know that setting this value to 0 disables the screen saver at the loginwindow.

Require Password

One more advantage to using the preference manifest - it can help you discover other settings that can be managed. When adding the new keys, you may have noticed another possible choice: Require Password. This key allows you to manage the setting to require a password after waking from sleep or clearing the screen saver. This is an important setting in many organizations to enforce computer security, and setting this via MCX in Leopard was tricky - Leopard's preference manifests contained only a manifest for com.apple.screensaver.ByHost, but setting Require Password there did not provide the desired result. To make things work, you needed to import preferences for com.apple.screensaver (minus the ByHost) and manage those as well. With Snow Leopard, Apple's cleaned this up so things behave as you'd expect.

Require password delay

To manage this preference, we need to discover the name of the preference key, so first we'll set it manually. Open System Preferences and choose the Security preference pane. Check Require password, and set the delay to 1 minute. Figure 7 shows the settings.


Figure 7 - Require password settings

Close System Preferences. Now we'll use the defaults command to find the name of the preference key we're looking for. We know the other key (askForPassword) is stored in com.apple.screensaver, so let's look there first:

> defaults read com.apple.screensaver
{
    askForPassword = 1;
    askForPasswordDelay = 60;
    tokenRemovalAction = 0;
}

askForPasswordDelay looks like what we need. Returning to Workgroup Manager, we can use the Screen Saver Loginwindow preference manifest to add the Require Password key. To manage the askForPasswordDelay key, just add a new key, click on its name and choose Edit. This allows us to add key names that aren't in the preferences manifest. You can type askForPasswordDelay as the name of the key. Change its type to Integer, and for the value, type the number of seconds you'd like as the delay before a password is required. When you're done, it should look like Figure 8. Note the Name doesn't match preference manifest warning - we can ignore this since we added this key intentionally.


Figure 8 - com.apple.screensaver managed preferences

Click Apply Now and Done, and log out and back in on a computer that is a member of the computer group you are testing with. If you open System Preferences and click the Security pane, you should see something like Figure 9. Note that Require password is checked, the delay is set to one minute (or whatever you set it to) and both controls are disabled, indicating to the user that they cannot change them.


Figure 9 - Managed screen saver password preferences

Other options

If you absolutely cannot or will not use MCX, even via Local MCX, all is not lost. You can still manage the screen saver over loginwindow, and can at least set a default behavior for Requires password and the delay.

To accomplish these tasks without using MCX, we can use the defaults command. To manage the screen saver over the login window (watch the line breaks - there are two commands here; each should be all on one line):

defaults write /Library/Preferences/com.apple.screensaver  
   loginWindowIdleTime -int 300
defaults write /Library/Preferences/com.apple.screensaver 
   loginWindowModulePath 
   "/System/Library/Screen Savers/Flurry.saver"

If your users don't have admin rights, this is virtually identical to using MCX to manage this, as there's no standard user-accessible way to change or override these settings.

You can also set Require password and its delay (again, two commands, each all on one line):

defaults write /Library/Preferences/com.apple.screensaver 
   askForPassword -int 1
defaults write /Library/Preferences/com.apple.screensaver 
   askForPasswordDelay -int 60

Unfortunately, for these particular settings, this is a poor substitute for MCX, as the user can override these settings with a visit to the Security pane in System Preferences. Without MCX, these controls will remain available in the Security pane, and the users may change them at will. Also, any pre-existing user preferences for the screen saver will still be applied. To come closer to enforcing these preferences, you'd have to write a script that deleted these preferences from the user's home directory so they wouldn't override the ones set in /Library/Preferences/com.apple.screensaver.plist, and also perhaps figure out a way to deny the users access to the Security preference pane. Once you start writing scripts to manage preferences that can be managed via MCX, you're better off investing the effort in getting Local MCX working.

Since these defaults settings are all stored in a single file - /Library/Preferences/com.apple.screensaver.plist - you could also use a software delivery tool like radmind or LANrev or Casper to simply install that file with the appropriate contents. Again, this would be effective for managing the screen saver over the Login Window, but less so for requiring a screen saver password.

Conclusion, and the future...

So there you have it. Apple has provided a new feature in Snow Leopard - the screen saver can now run over the Login Window. Even better, they've made sure it can be managed via MCX. We looked at several methods for specifying our managed preferences, using Apple's tools. And we also looked at a way to control the screen saver over the loginwindow even without using MCX.

Where might you go from here? If one of your goals was to manage the loginwindow screen saver so you could display a set of images that are specific to your organization - for example, artwork from your company, or images from a company event, or even advertising, you'll probably want to create your own slideSaver, and manage its preferences. But that will have to wait for another time! See you next month.


Greg Neagle is a member of the steering committee of the Mac OS X Enterprise Project (macenterprise.org) and is a senior systems engineer at a large animation studio. Greg has been working with the Mac since 1984, and with OS X since its release. He can be reached at gregneagle@mac.com.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Logic Pro X 10.3 - Music creation and au...
Logic Pro X is the most advanced version of Logic ever. Sophisticated new tools for professional songwriting, editing, and mixing are built around a modern interface that's designed to get creative... Read more
iMazing 2.1.8 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Civilization VI 1.0.2 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
TurboTax 2016 - Manage your 2016 U.S. ta...
TurboTax guides you through your tax return step by step, does all the calculations, and checks your return for errors and overlooked deductions. It lets you file your return electronically to get... Read more
Microsoft Office 2016 15.30 - Popular pr...
Microsoft Office 2016 - Unmistakably Office, designed for Mac. The new versions of Word, Excel, PowerPoint, Outlook and OneNote provide the best of both worlds for Mac users - the familiar Office... Read more
FotoMagico 5.3 - Powerful slideshow crea...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more
Acorn 5.6.1 - Bitmap image editor.
Acorn is a new image editor built with one goal in mind - simplicity. Fast, easy, and fluid, Acorn provides the options you'll need without any overhead. Acorn feels right, and won't drain your bank... Read more
Dash 3.4.3 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Microsoft Remote Desktop 8.0.37 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
Macs Fan Control 1.4.7.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more

Turbo League Guide: How to tame the cont...
| Read more »
Fire Emblem: Heroes coming to Google Pla...
Nintendo gave us our first look at Fire Emblem: Heroes, the upcoming mobile Fire Emblem game the company hinted at last year. Revealed at the Fire Emblem Direct event held today, the game will condense the series' tactical RPG combat into bite-... | Read more »
ReSlice (Music)
ReSlice 1.0 Device: iOS Universal Category: Music Price: $9.99, Version: 1.0 (iTunes) Description: Audio Slice Machine Slice your audio samples with ReSlice and create flexible musical atoms which can be triggered by MIDI notes or... | Read more »
Stickman Surfer rides in with the tide t...
Stickson is back and this time he's taken up yet another extreme sport - surfing. Stickman Surfer is out this Thursday on both iOS and Android, so if you've been following the other Stickman adventures, you might be interested in picking this one... | Read more »
Z-Exemplar (Games)
Z-Exemplar 1.4 Device: iOS Universal Category: Games Price: $3.99, Version: 1.4 (iTunes) Description: | Read more »
5 dastardly difficult roguelikes like th...
Edmund McMillen's popular roguelike creation The Binding of Isaac: Rebirth has finally crawled onto mobile devices. It's a grotesque dual-stick shooter that tosses you into an endless, procedurally generated basement as you, the pitiable Isaac,... | Read more »
Last week on PocketGamer
Welcome to a weekly feature looking back on the past seven days of coverage on our sister website, PocketGamer. It’s taken a while for 2017 to really get going, at least when it comes to the world of portable gaming. Thank goodness, then, for... | Read more »
ROME: Total War - Barbarian Invasion set...
To the delight of mobile strategy fans, Feral Interactive released ROME: Total War just a few months ago. Now the game's expansion, Barbarian Invasion is marching onto iPads as a standalone release. [Read more] | Read more »
Yuri (Games)
Yuri 1.0 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: It's night. Yuri opens his eyes. He wakes up in a strange forest.The small, courageous explorer rides on his bed on casters in this... | Read more »
Space schmup Xenoraid launches on the Ap...
10Tons Xenoraid is out today on the App Store, bringing some high-speed space action to your mobile gadgets just in time for the weekend. The company's last premium title, another sci-fi game titled Neon Chrome, did quite well for itself, so... | Read more »

Price Scanner via MacPrices.net

Laptop Market – Flight To Quality? – The ‘Boo...
Preliminary quarterly PC shipments data released by Gartner Inc. last week reveal an interesting disparity between sales performance of major name PC vendors as opposed to that of less well-known... Read more
IBM and Bell Transform Canadian Enterprise Mo...
IBM and Bell Canada have announced they are joining forces to offer IBM MobileFirst for iOS market-ready enterprise applications for iPad, iPhone or Apple Watch. Bell, Canada’s largest communications... Read more
Otter Products is Closing… For a Day of Givin...
On Thursday, Feb. 9, Otter Products is closing doors to open hearts. In partnership with the OtterCares Foundation, the company is pausing operations for a day so all employees can volunteer with... Read more
15-inch 2.2GHz Retina MacBook Pro on sale for...
Amazon has 2015 15″ 2.2GHz Retina MacBook Pros (MJLQ2LL/A) available for $1799.99 including free shipping. Apple charges $1999 for this model, so Amazon’s price is represents a $200 savings. Read more
Back in stock: Apple refurbished 13-inch Reti...
Apple has Certified Refurbished 2015 13″ Retina MacBook Pros available for up to $360 off original MSRP, starting at $1099. An Apple one-year warranty is included with each model, and shipping is... Read more
CalcTape for macOS 1.2 Adding Machine App for...
schoettler Software has announced CalcTape 1.2, an update to their desktop calculator for macOS. When it comes to adding long columns of numbers, doing complex calculations or playing around with... Read more
New MacBooks And MacBook Pros WIth Kaby Lake...
Digitimes’ Joseph Tsai cites a Chinese-language Economic Daily News (EDN) report that unnamed market watchers are predicting Apple MacBook shipments to grow 10 percent in 2017, and projecting 15... Read more
New 2016 13-inch MacBook Pros on sale for up...
B&H Photo has the new 2016 13″ MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar MacBook Pro... Read more
New 15-inch Touch Bar MacBook Pros in stock a...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
Opera Announces Neon Concept Browser For Mac
Opera is inviting users to get a glimpse of what Opera for computers could become with its Opera Neon browser concept. Each Opera Neon feature is described as “an alternate reality” for the Opera... Read more

Jobs Board

*Apple* Retail - Multiple Positions (Multi-L...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Stamford, CT We have immediate job openings for several Desktop Support Technicians with one of our most well-known Read more
*Apple* macOS Systems Integration Administra...
…most exceptional support available in the industry. SCI is seeking an Junior Apple macOS systems integration administrator that will be responsible for providing Read more
*Apple* Premier Retailer - Service Technicia...
DescriptionSimply Mac is the largest premier retailer for Apple products and solutions. At Simply Mac we are all Apple , all the time. Same products. Same prices. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.