You are a System Admin/Consultant and you have to deploy an application working fine on dev machine, but as soon as you deploy it on the production machine it does not work. What is the silliest configuration mistake you ever made?

  • 1
    this should be community wiki
    – Zypher
    Mar 16, 2010 at 17:36

5 Answers 5


I'm not sure these are silly enough, I must've done worse...

Almost 20 years ago, I was helping set up a new office and was getting the Internet connection going, setting up an HP/Apollo workstation as the main DNS server. I learned the hard way about the need to include the . at the end of FQDNs.

While changing some connection in the server room and simultaneously in a wiring closet, I hooked the switches up in a loop. It took a few seconds for the ports to saturate, and a few more to unplug the last few connections.

  • 2
    I think anyone who has ever hand-edited a zone file has done the "missing dot" thing at least once :-)
    – voretaq7
    Mar 16, 2010 at 17:19

Worst configuration mistake that springs to mind: Renumbering a server and making sure to adjust all my server's Listen directives, my IP-Based vhosts, and the system's network configuration...

...then rebooting and realizing I didn't update the local firewall to pass traffic for the new network. DOH!


I dont know if this counts or not. We were on a very tight budget and needed to run 10 new CAT5 runs to a location in the middle of a concrete floor. There wasnt any under-floor conduit available and the ceilings were cathedral with no crawlspace. There was a row of low-hanging florescent light fixtures directly over the location where the CAT5 needed to be installed. I proposed that we run the cat5 out of a wall at fixture-level, then run a piece of conduit 25' across the top of the fixtures to a column. Then down the outside of the column to a box.

This looked and worked beautifully for years....until maintenance was called in to change one of the florescent tubes....access to the light was via the top of the fixture...which is where I had mounted 25' of conduit.

That light still had not been replaced.

  1. Configure router for RADIAS authentication
  2. Think you have tested failback to LOCAL auth but havn't really because as that point in time your RADIUS and LOCAL passwords were the same
  3. Need to move RADIUS server to a less secure network to allow normal users to vpn in via the firewall
  4. Decommission Old RADIUS server
  5. forget about router, never change RADIUS config
  6. Try to log into the router ...

I'll give you 3 guesses as to how successful that was.

Luckily we only setup LOCAL authentication for serial line access (hey if you have access to the box to plug into the serial port ... well we all know the rule about physical access and security)


How about this?

  1. Configured the Web site fine, but accessing a .aspx file gave "404 - File or directory not found". ASP.NET Web Service Extension was not enabled.
  2. In IIS 7, you are planning to install SSL Certificate and under Request Certificate under Country code you don't see your country code. It can be added manually.
  3. You complain, Web site hosted in production is having high CPU problem. Forgot to diable debug="true" in web.config

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