Ultra Cheap ZFS Array

Make your own ZFS array (mirrored) with USB Flash drives, for cheap!

http://megalomaniacbore.blogspot.co.uk/2017/12/using-flash-drives-in-zfs-mirror.html

Since this... interesting post of mine... has only about 10 views, and my tech items usually get a few hundred, I figure somewhere along the lines it got trampled by my silly New Years post....

Bash : Power of Pipes

Subtitle: "Get IP Address Easily"

When I say easily, I mean not so easily, but with the proper tools... Let me explain, it's been one of those days... I've a remote server running some flavour of Linux, and no-one knows it's remote IP Address, they all SSH into the box run "ifconfig" and note down the value, they then plug this into a config (or worse still were baking it directly into some code) and running their services....

The trouble of course being, years later, they're no-longer the programmers nor maintainers of this machine, I am...

And to be frank whenever the IP address changes I don't want to recompile their java code, nor use vi to edit the various configuration files, I want a script to at least update the settings automatically.

I therefore changed their code to load the IP address, not hard code it, and used some other scripts to put the IP address into the config file at boot...

The first line of that script is what I'm going to document here... so it starts:

#! /bin/bash

ifconfig | grep inet | tr ' ' '\n' | sed -u '/^$/d' | head -2 | tail -1 > ipaddress.txt

This script gives me a single line of text with the IP Address in it, for the one and only adapter in the machine, if you have multiple adapters you'd have to play about with the grep inet to select the row you want with a head & tail call before moving into the  final location, or whatever...

I wrote this up however, and immediately started to use the IP address.

The net result was a request to explain all this functionality to a colleague... Here's what I came up with.

ifconfig gets us the adapter information...

grep strips off lines we don't want only giving lines for the inet adapter

translate turns spaces into new lines

the sed call removes the blank lines, giving just the IP address and some guff

the first adapter IP address is therefore always the second line of this output

we select the first two lines with head

then select only the latter of these two with tail

and write this to a file

Her reply... "What are the Lines?"....

"What lines?"...

"These | things"....

"They're pipes, I'm piping the information from one program to the next..."

"Oh"

"Do you know what pipes do in Unix and Linux?"

"No"

I sent her to this video... https://youtu.be/XvDZLjaCJuw?t=5m15s

SCO Out

I've been sad to read over the last few years about the woes of SCO, the once great Unix vendor; at least in my opinion.  At my first IT job there were minicomputers running a customized cut of SCO, I remember a new bunch of server hardware from Compaq coming in and the delight of the IT manager esconsing himself in the dark musty old design office (literally a dark dungeon) and getting on with installing the system.

He literally put the system together on the machine, set up the RAID and everything in the dark at the keyboard.

That job was my first taste of server operations on "medium" iron (minicomputers) and I've been fascinated with servers and setting them up ever since; not that my current employer has noticed this in any reasonable fashion.

Today though SCO are in the news as filing for the final embers of bankruptcy they're down and out and going to be gone, a shame, I remember their service as excellent here in the UK and their software... Well in two years tending the flaky NCR based minicomputer I never had it tip over and as far as I know the Compaq kit to replace it was destined to live out a life of 15 planned years...

At the same time I saw this SCO jump up a level I was introduced to the AS400 from IBM, and was woefully underwhelmed, the SCO running machine we'd just had set up cost in the region of 7K and was designed to run something like 15 sites throughout Northern England, as well as collate a warehouse, stock and tabulate sales.  The AS400 I was introduced to cost something in the region of 12K, was the near as makes no difference same specification, carried a huge service & support cost to it and was only going to run about 50 hand-held scanners and control stock in one warehouse... It literally beggars belief the different in performance.

So, with the going down of the Sun over SCO (no pun intended) I for one saulte the memory of that blue yellow and white packaging arriving, and how it brought that system alive through tender carressing, not through leaving the man in IBM white uniforms to their blackbox of tricks.

Burning up, or shutting down, the Mini-Computer

I've decided today to tell a story, its a true story, and it bares some interesting information and history.  You see, I used to work for a company called "Claremont Garments", at the factory in Selton, and I worked in an IT support Role... I took over the role from a guy called Jim... The last time I saw Jim he fell out of a doorway near drunk when I picked him up for the annual departmental curry... But anyway, I was a student at the time... Studying Software Engineering.

The company ran an NCR brand mini-computer, running serial lines through multiplexors out to the distant sites, using dedicated comms lines.  Meaning in the far off factories there were green screen terminals showing the computer screen.

At the time it was the sunset of the mini-computer era, I don't think very many companies still run in that fashion, though some, like the one I work for now, do still have powerful servers running systems which are really just old software which should have a terminal, but which have been given a GUI.

But at the time, I was introduced to this NCR, and its AST backup, machine I was told it had to have an ALWAYS UP rule, I was shown how to make a call on the very expensive support contract, then told the push button code for the door, and shown inside the cave of technological delights.

It was all pretty old stuff, a wire wrack, with monitors, keyboards, UPS's and other stuff, there was networking switches running down the right of the room, and computers down the left.

But as I'm being shown what each computer does, I notice that in the stream of air from the air conditioner there's black flecks... Soot... I look at the unit, its a nice newish clean looking thing... Where's this black coming from... I glance down, nothing, glance up... There are three monitors on the top of this wrack of machines, the right hand one is on, but looks fuzzy, and the black particles are floating out of it... The ceiling tile is slightly discoloured with heat... That bastard thing is on FIRE!

Well, I shift back, and point it out, Jim to his credit dives in to his elbows and grabs this thing down... As I reach around his arms and unplug it... But now, he's holding a burning monitor over his head, and is stood in the server room... There are two doors to this room, I sling the one to the right open and Jim hurls this monitor over hand into the corridor, where it just sits black specks floating and all...

However, turning back around the chat hired to write code for the mini-computer, Don, is skidding into the other doorway and lands on the floor full length staring at the NCR... "What have you done?"  he cries "It's gone off"...

I look as puzzled as Jim, who retraces his steps... Whilst valiantly saving the server room from fire, he'd stood on a pile of wires, one of them was a coil of power lead, it was the lead from the UPS to the NCR... The NCR had lost power, instantly...

OH SHIT... Don and Jim reboot the machine, something I take care to learn about, but ironically in my whole time there, never had to do.

But then I take a look at the wire Jim "Pulled" out... it has screw fixings, it should have been screwed into the UPS and the NCR, but it wasn't... The person responsible for it not being screwed in, forever after, ridiculed Jim for unplugging the machine... But Jim had stood a good 4 feet to the side of the NCR itself... this chain of catastrophe should never had happened.

However, it did, and instead of Jim being remembered for his efforts to save the place burning up, he was always jibed and remembered for unplugging the NCR.