Sysadmins aren’t (necessarily) programmers, they’re people who can program

I remember back when I was first learning Linux, and I encountered shell scripts. I wasn’t a programmer, and I didn’t “get” it. I distinctly remember thinking, “well, THAT’S something I won’t have to learn”. Ha!

As it turns out, I was incorrect. Writing scripts is an essential skill for a system administrator. In Linux/Unix, we’re blessed to have an amazing development environment, where as administrators running on Windows had to make due with batch files until the dot net revolution came along to introduce ASP and VB script. Now, with powershell, they’ve actually got a great environment to write systems scripts in. Between that and things like Windows Server Core, I’m beginning to wonder about the Redmond camp. But I’m digressing…

Writing scripts isn’t an optional tool in an effective administrator’s tool belt. It’s absolutely vital to efficiently performing many, many tasks. Personally, I use the bash shell, because it’s the default, and it’s what I started on. You should use whatever you feel comfortable with, whether it’s a shell script or perl. Heck, I’ve been desperate enough to even do a couple of things in CLI-mode PHP, just because I’m more fluent in it than I am perl (which is a shame, and something I’m going to be working on rectifying).

My last “fun” bit of shell programming was probably a cron job that checked for a new tsunami warning and emailed me the text of the alert. Before that, I wrote an entire RSS reader in bash. With bookmark support. Yeah, I’m a sick man.

What kind of fun things have you done with scripts lately?

What is Cat5e?

Everybody knows, if you’re still dealing with Cat-5 to use Cat-5e. I mean, Cat-6 would be better, but it’s still really expensive to have installed. So we use Cat-5, except it’s ENHANCED for that extra special protection against interference and crosstalk. But what is it? What, if any, is the actual, real, honest-to-God, difference between Cat-5 and Cat-5e? I’ve read the wikipedia entry, and while informative, it could really do with a rewrite. One of the few sections that mentions Cat-5e is The Cat 5e 350mhz debacle. The title makes me believe that maybe the 350mhz denotation is how you can tell, but then it goes and says this:

“Although the performance of this new 350 MHz cable was slightly better it was an easy way to sell the consumer on future proofing their needs while charging around 15% more and leading to a higher margin on the 350 MHz cable than the standard 5e cable.”

Well, alright then, what IS a standard 5e cable?

I looked at some more resources, and found some sadly incorrect suggestions and no real answers. For instance, this wiki answers post says that you need Cat-5e to get Gb/s speeds, that 5e is rated at 350mhz, and that there’s less crosstalk (though it doesn’t say why). Of course, it also says “Unless every single component in the network is gigabit rated, then you will never have a gigabit network, because your network will always run at the speed of your slowest device.”, so you can understand my skepticism.

The second table on this page sounds pretty solid, basically displaying that there are standards for Cat5E that don’t exist for Cat5, with the assumption that the cable meeting those standards will perform better/faster than a cable without those particular requirements.

But of course, I wanted to ask, because you can’t trust everything you read on the internet. Case in point?, who either desperately need to update their page, or desperately need to stop taking drugs:

“The Simple Answer:
CAT-5 is rated to 100M
CAT-5e is rated to 350M
CAT-6 and CAT6e is rated to 550M or 1000M depending on your source
CAT-7 is supposedly rated to 700M or presumably 1000M

Today there is no approved CAT-6 or CAT-7. While some folks are selling products they call Level 6 or 7, there aren’t even specs for them, making CAT-5e the best available option.”

Sad, really. I blame the schools.

So now I ask you. I assume that there is an actual, real difference between Cat-5 and Cat-5e. what is it?

It appears that Cat-5 cable is defined by the TIA/EIA-568-A standard. The only time I’ve ever paid attention to that standard was when crimping my own ends, because TIA/EIA-568-A specifies the order of the wires in the RJ45 (really 8P8C) end. It also uses the green pair first, which I thought was weird, since I learned orange first.

However, when I go to the TIA/EIA-568-A wiki page, I’m redirected to the TIA/EIA-568-B page. At a table way down at the bottom are the lines:

Cat 5: Currently unrecognized by TIA/EIA. Defined up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.

Cat 5e: Currently defined in TIA/EIA-568-B. Defined up to 100 MHz, and is frequently used for both 100 Mbit/s and 1000BASE-T Gigabit Ethernet networks.


I still don’t know what the actual difference is, aside from orange going first in Cat-5e, apparently, but hey, more light on the subject, I guess.

Also, it appears that Able Cables had someone research a write a paper on the differences on the difference between TIA/EIA-568A and TIA/EIA-568B. Here is his conclusion:

9.0 Conclusion

Historically 568B was the specification on choice due to its early development and implemented base, but as the market and the political climate has changed over the years 568A has become the more dominate and preferred specification. This is only due to a desire by world standards organizations to provide a specification as backwardly compatible as possible. All new installations should be carried out using the 568A standard and cables only to be terminated to 568B specification on existing 568B systems.

Honestly, I’m not entirely sure what to make of that.

Can anyone here with more cable experience give me a hand?

BTW, I also posed this question on serverfault.

Administering Users in Linux via CLI

The other day, I mentioned that my review of LISA ’09 was published in Linux Pro Magazine. Well, I went to the bookstore to pick up a copy. It wasn’t there, but to my surprise, I saw the special “Linux Shell Handbook” edition was out, which includes a four page article that I wrote about administering users in Linux with the command line tools! How cool! So I picked up a copy for my junior admin and another to read myself. Very neat to see my name in a printed magazine. I can’t wait to see it on the cover of a book!