On a Mac, if you SHIFT-CLICK the green dot on a window it opens it as wide and tall as possible (instead of the application-defined behavior)
Even though "ls -l" displays a files permissions as "-rw-r--r--", you can't use "-rw-r--r--" in a chmod command. This is probably one of the most obvious but overlooked UI inconsistencies in Unix that nobody has fixed after all these years. Instead we force people to learn octal and type 0644. Meanwhile every book on Unix/Linux spends pages explaining octal just for this purpose. Time would have been better spent contributing a patch to chmod.
If a network problem always happens 300 seconds after an event (like a VPN coming up or a machine connecting to the network) the problem is ARP, which has to renew every 300 seconds. Similarly, if it times out after exactly 2 hours, the problem is your routing system which typically expires routes after 2 hours of not hearing them advertised.
Git rocks. I should have converted from SubVersion to Git years ago. Sadly I like the name SubVersion better. I hear Hg / Mercurial is better than Git, but Git had better marketing.
Keep all your Unix "dot files" in sync with http://wiki.eater.org/ocd (and I'm not just saying that because my boss wrote it).
People that use advanced Python-isms should not complain when I use features that have been in bash forever and, in fact, were in /bin/sh before most of us knew how to read.
Years ago IETF started telling protocol inventors to avoid using broadcasts and use "local multicast" instead because it will help LAN equipment vendors scale to larger and larger LANs. If your LAN network vendor makes equipment that goes south when there is a lot of multicast traffic because it is "slow path'ed" through the CPU, remind them that They're Doing It Wrong.
The best debugging tool in the world is "diff". Save the output /tmp/old. As you edit your code, write the output to /tmp/new then do "diff /tmp/old /tmp/new". When you see the change you want, you know you are done. Alternatively edit /tmp/old to look like the output you want. You've fixed the bug when diff has no output.
Attend your local sysadmin conference. Regional conferences are your most cost effective career accelerator. You will learn technical stuff that will help you retain your job, do your job better, get promoted, or find a new job. Plus, you'll make local friends and contacts that will help you more than your average call to a vendor tech support line. There are some great ones in the Seattle and NJ/NY/Philly area all listed here.
Random technical tips, thoughts and rants
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