System Administration

Dear IT professionals and architects, If we’re having a contest it’s about seeing how simple we can make things, not how complex. Yes, I know you can run blah in blah with blah against Amazon S3 in a grid with J2EE and blah and blah. The more crap you stack on each other the less likely it is to actually work right beyond this point in time. While you’re dreaming up Rube Goldberg IT inventions I spend my time tearing them down and replacing them with simple systems that just work. …Bob P.S. I don’t care if you are an “architect,” you’ve obviously never had to support one of these things. ——————————————– Dear IT managers, The simplest solutions are the …

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I mentioned in some comments the other day that our EMC CX700s hadn’t blown a storage processor lately. Ha! Today ends the streak.

“About 10,000 Juneau residents briefly lost power after a bald eagle lugging a deer head crashed into transmission lines.” I was going to put this in my del.icio.us bookmarks but it just didn’t seem like the right place. I am consistently in awe of raptors.

On my PCs write caching wasn’t enabled by default for my system disk. Turn it on in the device manager (Right click “Computer”, choose “Properties,” choose “Device Manager” from the sidebar, expand the disk drives category, right click your drive, choose “Properties,” pick the “Policies” tab): I don’t suggest enabling this for removable media, as it pretty much guarantees data loss if you remove the device without stopping it first.

Do you ever open your desk drawer and find that someone has borrowed your screwdrivers without returning them? Yeah, me too. I keep a decent set of tools in my office. I got this habit from my father, who basically had three sets of tools: one that went with him in his vehicle, one in the garage workshop, and one in the basement workshop. A good quality tool was never far away from where you needed it. Everybody knows I have a toolbox at work. I’ve made it clear that people can borrow the tools as long as they return them. It is inevitable, though, that eventually I can’t find my screwdrivers. Screwdrivers are the single most popular item, and …

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With Apache httpd, any requests that come in that don’t match a VirtualHost stanza get serviced by the first VirtualHost available. You can often test this by browsing with your web server’s IP address. What site do you see? Is that what you want people to see when they didn’t know what they wanted to find? My suggestion: create a “dummy” virtual host that will return a blank page, or redirect to a known place. Put it first in the list of virtual hosts so that visitors get to see what you want them to see, not some other web site.

We use Sophos PureMessage to scan for spam and viruses. We had eight Dell PowerEdge 2650s with varying CPUs and RAM clustered with a Alteon Layer 4 application switch. Our mail systems (sendmail and Sun Java System Messaging Server) use the PureMessage connector to speak to this cluster. The Layer 4 switch is set to balance the connections with a least-connections weighted algorithm. The amount of spam we’ve had to deal with has tripled in the last 12 months. As a result this cluster was starting to max out. There are two ways to think about mail volumes: peak and overall. When someone says that they handle 15 million messages a day they don’t usually mean 625,000 per hour, or …

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Annoyed that Windows XP and Vista get a temporary IPv6 address, in addition to the autoconfigured one, and anything you’ve set manually? I was, until I figured out how to shut it off: netsh interface ipv6 set privacy state=disable This way you can assign a static IP if you like, or at least use the less random one assigned with autoconfiguration.

As time goes to infinity the stability of a computer system goes to zero. I don’t know if anybody else has said that, but it’s a law in my life as a system administrator. As you install and remove software you change systems in subtle ways. These changes aren’t reproducible, they’re undocumented, and they are unpredictable. At the very least you end up with extra files littering your systems. At the worst your system becomes less stable. Now imagine what happens when you install a new operating system, the biggest of applications, over the top of an old one? This leads me to a corollary: Do not upgrade systems in place. Always rebuild them. Upgrading a system just lets the …

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