October 2007

Ubuntu 7.10 (Gutsy Gibbon) (though I keep typing “gusty”) was released today. I tried the upgrade directly from my Feisty 7.04 desktop, using update manager. However, though things started well enough, soon enough my download speed had dropped to 20kb/s and my estimated completion time had trailed off to 22 hours. Ack. Not nearly quick enough for me, since I’ve been impatiently waiting for the non-beta release for days.

So, what’s the alternative? As usual, bittorrent provides speedy downloads for popular files, and this one counts. To upgrade a current installation, get the .torrent file for the 7.10 alternate iso image from the Ubuntu 7.10 Releases page, and open it with your favorite torrent application. My speed is about 25 times faster downloading via this method. I will be seeding the file when I can, as well, to make sure this process is as fast for others as it can be.

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If you stay online long enough, you’re bound to find convergences in ideas where you weren’t looking for them.
Here’s where my net trail led me:

From when I first started working with Unix up to the nearly present, I had always used cat /dev/null to empty a file with a minimum of mess, i.e.,:
foozbear% cat /dev/null > big_useless_log

This, of course, made big_useless_log empty, and did so without getting rid of it, in case an a data write was imminent. If memory serves, this was all very consistent with the Unix principle of “First, Do no harm,” or, “Don’t make waves if you don’t have a board,” or whatever it was. (I believe using /dev/null in this way was called data lavage.)

This week I was using a lot of temp files — actually using the same temp file over and over to hold data I’d scraped from Cisco switch output so I could point some ‘awk’ at it for parsing purposes. For some reason, I decided to see what would happen if instead of removing and recreating the file (or more laboriously, typing cat /dev/null > temp), I used a redirection symbol, i.e.,
foozbear% > temp
Well, this worked as well as my previous steps, so I started alternating (using the command line up arrow) between my temp file resetting/editing
foozbear% > temp && vi temp
and my grep/awk line:
foozbear% egrep 'Gig|Fas' temp | awk '{print "interface "$2" "$3"\n description "$1}'

This worked fantastically (note that I was using bash under Ubuntu here), and a good time was had by all (the Cisco switches were particularly pleased, having their cdp output turned into port descriptions so handily — but perhaps I’ll expand on that later).

The redirection symbol also can be used if you are too lazy to create an empty file using ‘touch’. Instead of
foozbear% touch newfile
just type
foozbear% > newfile
and you’re all set.

I thought I’d post the simple filter I use on ’show cdp’ output, which lets me get information quickly.

MalbecMDF#show cdp neighbor detail | include (---|Device ID|IP address|Platform)

In practice, I generally cut the command down to:
sh cdp ne d | inc (blah|blah)
It is probably best to start with obvious match choices, before pairing them down, as you can find yourself surprised with the text that is grabbed from different types of devices if you’re basing your regular expression match on a small sample.

In any case, the output should come out something like this:

MalbecMDF#sh cdp ne d | inc (---|e ID|IP add|Plat)
-------------------------
Device ID: SummaC-6509
IP address: 10.77.234.131
Platform: cisco WS-C6509-E, Capabilities: Router Switch IGMP
-------------------------
Device ID: Malbec-AP10
IP address: 10.88.129.22
Platform: cisco AIR-AP1231G-A-K9 , Capabilities: Trans-Bridge
-------------------------
Device ID: Malbec-AP11
IP address: 10.88.129.29
Platform: cisco AIR-AP1231G-A-K9 , Capabilities: Trans-Bridge
-------------------------