Secondary DNS Configuration

I recently had occasion to do some Mac OS X DNS configuration. Primary DNS setup is pretty straightforward, but I always get stuck on the secondary DNS config, and this week I had the (not so) rare privilege of discovering I'd been doing it wrong all along. I thought I'd post some quickie instructions for next time this comes up.

So, to set up your Mac OS X Server as a secondary DNS server (that is, if the primary goes down, this one will act as a failover), you'll need to open Server Admin and navigate to the DNS section (we'll use the 10.4 version, but the basic gist is the same in 10.5). Next, add a secondary zone under "Secondary Zones." This first one will be for your forward lookups. In the first field add the full name of your zone. In the second field add the IP address of your primary DNS server. It should look like this:

Secondary DNS: Forward Lookups
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Now add another secondary zone for the reverse lookups. This is exactly the same except that instead of the zone name in the first field, you'll use the reverse zone information. It looks like this:

Secondary DNS: Reverse Lookups
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Note that the reverse IP in the field should cover the zone IP range. That is, if your primary DNS server covers "192.168.1" zone, you'll enter the reverse info for that range. If your primary DNS covers all of "192.168" (notice the truncated IP number) then you should enter that. All together it should look like this:

Secondary DNS: All Together Now
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Once this is all set up and saved, you can start the service. You can tell it worked by listing the contents of /var/named. You should see two new files, one called your.domain.com.bak and one called your.IP.in-addr.arpa.bak. And these should be populated with the same DNS info as your primary.

And that's it! Enter the new secondary DNS server info in your Network System Preferences, just after the primary, and if your main DNS fails you'll be covered.

Oh, almost forgot, thanks to this dude for helping me figure all this out.

NetBoot Part 2

So here's the plan, as it stands right now. (Yes, I have a plan already! Yes, that was quick.) First, build an image that's good for all workstations (laptops, staff machines, standard workstations, etc.) throughout the lab with:

• Base OS (Mac OS X Leopard 10.5)
• A DHCP network connection
• Apple applications
• Adobe applications
• Drag-and-drop applications
• Other third-party applications
• One admin user
• ARD active

IMAGE THIS SYSTEM
This becomes the base system build, the Master Image — the replacement system if a machine ever needs rebuilding. It is the only full system image. There is only one.

Everything else that is machine-type specific — that is, users, applications, application components, crontabs, anything — gets turned into and installed via either a downloaded or hand-rolled package. So far I've been using Apple's PackageMaker, which has matured a great deal since last I tried it. It's pretty nice. I'm also taking a look at Iceberg, which also looks to be pretty full-featured and nifty.

Iceberg: by White Box

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PackageMaker: by Apple
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These packages can be machine-type specific and stored in a simple folder hierarchy by machine type — laptop packages in the laptops folder, etc. — for organizational purposes. In addition to being machine-type specific, packages can also, I believe, be machine specific. That is, I think we can make settings like computer name and network settings using packages as well. So what we're talking about here is a system of computer building that happens completely over the network, and that can be directed almost entirely from one ARD-toting computer, that computer being mine, of course. (I've always said, the sign of a good SysAdmin is that he never leaves his chair.)

I've gotten pretty good at making application packages, at this point (not that it's terribly hard, mind you). My next step will be to learn how to make system settings with packages as well. My other next step is going to be, of course, creating the Master Build. None of this building happens 'til summer. But still, something tells me it's going to be smart to start this process now and see what crops up over the next couple of months.

As usual, I'll be reporting any new and/or interesting developments.

Oh, and thanks to everyone who commented on the last post. The comments were extremely useful!

Tiger Hates Leopard

So I'm sitting in my office, waiting for the Mac OS X 10.5.2 Leopard update to show up in my Software Update, and it just isn't happening. And at some point I realize, "Hey, maybe it just hasn't been downloaded to our Software Update Server yet." Yes, we run our very own Software Update Server under Mac OS X Server 10.4. It's super cool. It downloads all Apple updates to itself, and then any Mac in our lab can get all the Software Updates from our own internal server, rather than Apple's, which just saves gobs of time and bandwidth. Oh, we love it. But there appears to be a catch: Tiger Server will not download Leopard updates.

So I'm sitting there waiting, like, forever. And the 10.5.2 update never shows. Nor does the Leopard Graphics Update, or the HP Printer Drivers Update, and I'm all like, "Dude, what the fuck?" When all of a sudden the iLife Support Update does show up.

And that's when it hits me: Tiger totally hates Leopard.

But that's okay, 'cause Tiger's a total bitch.

In any case, I'm not sure if the converse is true — if Leopard Server will fail to download and serve Tiger updates — but if it is, good luck running a Software Update Server in a mixed Tiger/Leopard environment. Geez! You'd think Apple's software would be more compatible with, um... itself!

Highly annoying.

Oh, and by the way, after removing my Leopard box from the SUServer client list, these commands got me back in business without a restart:

sudo killall DirectoryService

sudo dscacheutil -flushcache

Just so you know.

UPDATE:

It would appear that Leopard's Software Update Server is a bit less finicky when it comes to older updates, for previous versions of the OS. Hmmm... Do you get the feeling Apple's trying to tell us something? (You know, like, "Upgrade your server." Or something.)

Leopard Software Update Server: Backwards Compatible

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NetBoot Part 1

My big, fat, self-assigned new project — or, as I like to call it, the bug up my butt — is system roll-outs. That is, I realized at some point two things. One, I am managing way more computers than ever before, and way more than I realized; and two, the scope and variety of these various systems has become increasingly wide. These realizations inevitably brought me crashing, headlong (yes, headlong) into a third and final revelation: I need to come up with a better system for managing machine builds and systems roll-outs.

Enter: NetBoot.

Actually, let me first explain how we've handled this in the past. When I began this job we had maybe 15-20 Macs running OS 9 briefly, and then OS X since about its inception. Mac OS 9 was notoriously easy to build. Just copy that shit and be done with it. But Mac OS X was a different beast entirely. Mac OS X was complicated. Moody. A tougher nut to crack. Mac OS X required me to delve into the dark arts of system cloning.

Cue thunder clap, scary music.

The process that eventually evolved was cloning over firewire. We'd build our master machine — a basic Mac OS install with all the latest updates and our requisite software — and then clone that to the other machines over firewire, with clients booted into our Master via firewire target disk mode. This was a quick and dirty way to build a bunch of systems. Once the group was built we could customize machines or groups of machines as we saw fit. For a lab of 15-20 Macs this has worked swimmingly. But our lab has grown slowly and steadily, and completely without my realizing it.

My latest count shows our lab at more like 50 Macs now. We've added a bunch of stuff: laptops, servers, more A/Vmachines of various configurations, a render farm, and of course more workstations. Using our old system of firewire cloning is becoming increasingly clumsy, slow and error-prone. We need a better way of doing things.

Okay, now. Enter: NetBoot!

Leopard's NetBoot Interface<
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NetBoot is Mac OS X Server technology that allows for centralized storage of and access to system images for installation over the network. The way it works is this: You build a system, trick it out, make it perfect — this is your Master System. Put it on a firewire drive or something transportable, because you can't be booted from your Master System for the next series of steps — imaging. Run the application called System Image Utility, that comes with Mac OS X Server's server tools, and create a NetInstall image from your Master System. Load that image onto your server and enable it in the NetBoot settings in Server Admin. And what happens next is something akin to magic (unless you use Linux, and then it's pretty par for the course, I guess.)

The Network Boot Volume: So That's What It's For!>
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With your NetInstall image enabled on your server, go to any client system and open the Startup Disk Preferences. Where you'd normally see the "Network Startup" icon (I'll bet you always wondered what that was for), you'll now get something a bit more descriptive. You should now be given the opportunity to boot from your master image. Choosing to do so will incur further magical results. Your system will now boot... Over the network! What's even cooler is that you'll be booted into the same basic installer environment you'd see if you were booted off a Mac OS X install disc, and you'll be walked through the steps required to install your Master System onto your computer. Um... OVER THE NETWORK!

There are some immediate advantages to a system such as this. First off, you can have a bunch of different Master System images for various build configurations in your lab. For instance, we can have a separate build for laptops and desktop machines. Cool! Also, this can all be automated (thanks to Automator integration) to make the process run almost entirely unattended. Sweet! And since the whole thing sits on the server and is available at all times, if a machines needs a rebuild, you just set it and forget it. Awesome!

But NetBoot has its drawbacks as well. Images — particularly large images — take for-freaking-ever to build. To give you an idea of how long, my near-36GB boot drive took an hour or so to clone to firewire, then 3-4 hours to be imaged by System Image Utility. So each build will take several hours to create. And God help you if you make a mistake on one of your images: the NetInstall images are read-only and can't (to my knowledge) be modified once they're built. NetInstall technology can't be used for non-package installers or updates either (again, to my knowledge), so you'll have to run all your Adobe and Microsoft updates by hand as usual. Also, one minor caveat that threw me at the outset: Mac OS X 10.5 server can only serve Mac OS X 10.5 builds. So you'll either be needing to update everything to Leopard or wait until your server and client OSes match.

I think I'm right on the crux of really needing this. I could probably live without it. Keep doing what I'm doing. But I do think I'm at a point where the benefits of using NetBoot outweigh its limitations. And I have enough resources now (like the required massive drive space and robust stable servers) that it's not impractical on the physical level. So, this summer I plan to use NetBoot to build my lab.

I mean, imagine this: you get your new systems over the summer, you unbox them, plug them into your network, set them to NetBoot (everybody say "command-n"! Good!) and go home for the night. You come in the next day and everything's basically done. You've just built your lab. Overnight. In your sleep. I don't know. Sounds pretty cool to me.

I'll let you know how it goes.

Oh, and by the way, in case you can't tell, I'm just now learning all this. It's still very new to me and there is a lot about it I don't know. So if anyone has any experiences or insights into using NetBoot (or if I get any of the facts wrong), I would absolutely love to hear about it. Please feel free to share your experiences in the comments.

Duplicate Computer Names and IPs

So there's an incredibly annoying and puzzling behavior in Mac OS X with regards to duplicate computer names on the LAN. Most Mac Admins probably know what I'm talking about. Here's the deal: Let's say you have a Mac Pro on your home network named Spanky and it has an IP address of 192.168.1.25. Let's also say, for the purposes of argument, that your best friend — who likes to emulate you in every way — has a Macbook named Spanky with an IP of 192.168.1.25 on his home network. (Hey, it could happen.) Now let's say your pal decides to come over, and he decides, "Hey, I think I'll bring my Macbook over so we can swap some illegally obtained music and pornography." He gets to your house to find you happily surfing the 'net. He whips out his Spanky and plugs it into your network, fires that puppy up, and Bam! All of a sudden your Mac Pro locks up. You can no longer surf. And you get an error message that looks a little something like this:

Duplicate Computer Name Alert: Why Me?
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You go to your Sharing Preferences (or your Terminal, or what-have-you) and, sure enough, your computer has been renamed. Renamed! WTF! Why is your computer, on your network, suddenly called "Spanky-2"? Because that's how Mac OS X handles duplicate computer names on the same network. It renames the existing computer to existing computer-2. Not the intruder. Not the new kid on the block. Your computer is now the computer formerly known as your computer. Why, it's pure genius, I tells ya! Brilliant!

Seriously, what in God's name were they thinking? Because, the way I see it, this goes beyond annoying into the realm of the dangerous.

Case in point: Let's say your Mac Pro Spanky is actually a server that provides services — authentication, Kerberos, LDAP, file sharing, the works — for a network full of computers. And let's say your friend is actually a guest on that network. When that guest plugs his computer into your network, and it just happens to be named the same thing as your server, God help you. You just lost — well, I'm not sure how much, but — a significant portion of your services. And all it takes is a computer name? I can rename any Mac on any network from any other Mac on that network by just changing my Mac's name? What's more, if you can get the IP of that server, you can bring it down entirely. That is total shit.

Strangely, it's been this way for at least three iterations of the OS now — since 10.3 — and it's still this way in 10.5. I am appalled. Can someone please explain the rationale for this to me? Please? 'Cause from where I sit, this is a major security flaw. To my mind it makes way more sense to have the newly installed machine make changes to it's configuration than to essentially be able to force changes on another machine. It's just backwards. And dangerous. And it desperately needs to be fixed.

UPDATE 1:
Mat X points out two very important facts: 1) the name change in this instance should only affect the Bonjour (.local) name of the duplicate machine, not it's actual name (the name it calls itself) or it's FQDN (the name as resolved by a DNS server), and 2) a client name change on the LAN should not be able to bring down a server with the same name because of the previous fact.

Dude, you're totally right, though I have seen, way back in the old days (10.2 maybe?) a duplicate name kill a server. So it did used to be possible. Nowadays though, Mac OS X Server has better, smarter naming conventions that prevent such things. I will say, though, that what prompted this was that I booted a clone of my own machine up on the LAN (same name, same IP) and it killed my computer, internet-wise, probably more because of the duplicate IP address. It's possible that all would have righted itself over time if I'd waited to see. I was just so annoyed by the behavior that I went on a bit of a rant. I still think it would be better behavior to leave the existing LAN client alone and make changes only to the new Mac on the LAN. But still, I got a little carried away.

Thanks for keeping me on my extremely bitchy and unscientific toes!

UPDATE 2:
So I've been doing some more testing on this issue. And while duplicate names on the network will not bring down your Mac OS X Server, a duplicate IP address will. Here's what I did:

1. I changed my client's IP address to match that of the Mac OS X Server (both Leopard 10.5.1). My machine got kicked off the internet and I got this warning:
   
2. I rebooted my client machine. Once the client had rebooted, the server got the above alert.
3. At which point the server could not ping out to the internet. Bad Mac OS X! Bad!

So, while my rant is partially in error, there does seem to be a bit of a flaw in the way Mac OS X handles new duplicate clients — particularly duplicate IP addresses. And I maintain that a better way would be to only modify the behavior on the most recent addition to the LAN.