Fettled any computer stuff today?

[Morat]

24 Cat5 cables mostly for wall sockets, some CCTV and WiFi APs.
My life is FULL of glamour 

whiteorangeorangewhitegreenblue....

[Feanor]

The switches wot I did blag when our former workplace closed down are stackable.

This means that rather than just linking them with a Cat 6 cable, you can link them over HDMI.
In this config, the top switch becomes the 'master', and the stack of switches below become 'slaves'.
The slave switches no longer have management IP addresses; they are all managed as one great big switch from the master.
The slave switches become just extra ports.


Master / Slave by Ron Lowe, on Flickr

[Kim]

This means that rather than just linking them with a Cat 6 cable, you can link them over HDMI.

*boggle*

I mean, sure, it makes sense as a way to throw zillions of bits around, but still...

[T42]

^^^ read that as "billions of zits". Partial dyslexia has its compensations.

I haz fettled da missus's HP printer, which wasn't.  Main impediment hitherto has been (a) presence of hovering missus, (b) her wretched ergonomic holier-than-thou fucking µsnot French keyboard with half the letters worn off,* and (c) my failing UNIX nous.  I installed a German KB while she was out and could shoot through the HPLIB reinstallation without having to hunt down every second letter and kill it.

I plugged her F(-ing) KB in again afterwards and, as a special favour, told her Ubuntu to use it.

*my beautiful old electromechanical Acer 6152 UV KB is three times as old and all the keys are perfectly legible.

[Afasoas]

HDMI for stacking switches used to be fairly common. Now it's all about the fibre interconnects.

You probably already know this, but I'd use both stacking ports on each switch with dual HDMI cables as to provide redundancy.

The main point of stacking is redundancy. Two or more network ports in each switch are configured into a single port channel (or LAG) and plugged into connected devices (usually servers) having two or more network ports bonded together. That way, a single network connection is made up of multiple physical links into different switches and thus when one of said switches in a stack conks out, it doesn't take the whole network with it.

I imagine those switches are pretty power hungry - one of the reasons I'm running a single 'prosumer-esqe' switch at home - as much as I'd like stacked switches and LAG to all the servers, it's just not worth the energy cost. If I was away from home more often, I would probably dig into it, as well as running redundant firewalls and making all network services highly available (N.B. running on at least two servers)

[Afasoas]

I completed the 'frankenvisor' build yesterday - or so I thought.

Frankenvisor is (or will be) a server dedicated to running virtual machines (hypervisor). It's a dual CPU which ironically, given the age of the parts is still less powerful then my now 5 year old desktop PC. However, it's 8 cores / 16 threads should make it more useful. And with 18 DIMM slots, I can get 72GB RAM using cheap 4GB DIMMS. 8GB DIMMS are way to spendy! The build involved epoxy, velcro tape and dremelling to make it all fit together. That means 'frankenvisor' a suitable nickname.

Unfortunately, I found that the two case fans don't spin up unless PWM fans are plugged into all of the motherboards fan headers. So I've got to get creative again in bodging another 4 fans into the case. 

Also found my power meter is broke, so I'm not as yet able to determine what it's power envelope is. I've opted for Xeon L5630 CPUs which are 40W TDP, so I'm hoping it's not more than 120W. Fortunately I'll be able to switch it on and off remotely thus it won't be running for more than a few hours each week.

[Kim]

I imagine those switches are pretty power hungry - one of the reasons I'm running a single 'prosumer-esqe' switch at home - as much as I'd like stacked switches and LAG to all the servers, it's just not worth the energy cost. If I was away from home more often, I would probably dig into it, as well as running redundant firewalls and making all network services highly available (N.B. running on at least two servers)

On the basis that switch failure would ruin my day, I've got a second identical switch above it in the rack, unpowered, with the same config.  Sure, it means swapping all the cables over, but that's a lot quicker than trying to find a replacement switch in a hurry.

High availability is overkill for what I'm doing at home.  I have redundant backups, and try to ensure that there's a desktop that's parts-compatible with the server.  I should be able to bodge my way back from most things within a day or two.

[Afasoas]

That's the point I'm working to with the firewalls - pfSense is virtualised on the main server. The backup server has an identical quad port network card in it. In fact, it's running on identical hardware, almost. All I need is a CPU upgrade to something with the VT-d/AES-NI support and then to nightly snapshot and backup the pfSense virtual machine - so in the event of the primary dying, all I've got to do is re-plug 4 cables and press a button.

Getting a second identical switch with which to do the same thing is utter genious.

[Vince]

I'm building a MIDI lighting controller. I did the prototyping with an Arduino Nano pushed into a breadboard kit and happily got the five faders and joystick working leaving one spare analogue channel.
Move on and create a smart aluminum panel with slots for the five faders and a hole for the joystick and then look at the Arduino controller that I will be using... It only has 6 analogue channels! BAH!!!!!1!!
(Note - I can't use the Nano as it doesn't allow re-programming the USB interface as a MIDI device)

My solution:
by Vince Hall, on Flickr
Two multiplexors, one for digital and the other for anaolgue I/O. Took a while to realise that unused analogue inputs must not be left floating.
 I'm quite proud of this solution as its the first time I've played with logic chips for several decades.

[Kim]

A long time ago in a galaxy far far away, I hacked up an 0-10V analogue lighting controller on veroboard that looked much like that.  It worked admirably well as long as you didn't touch the back side with sweaty fingers...

[David Martin]

The ADC chips work really well over I2[CS] (can't remember which) and give you loads of channels (8 for each MCP3208). IME they work absolutely fine with an Arduino or a Pi.

[Afasoas]

Frankenvisor now has a full compliment of fans and has been installed into the rack. Some eegit configured the out of band management interface on the same IP as the installed OS. 
With that resolved, ran into problem number two. Shutting it down either via the power button or the OS results in it booting back up again. Which is kind of awkward when it's running headless and I've no intention of running it 24/7.

That said, I spun up the first VM under Proxmox, and that seems to work. Acquired a pair of Ubiquity Unifi UAPs for less than the price of a single decent Wireless Access Point. These will be pressed into service as replacement for an ailing TP-Link AP that's periodically throwing it's toys out of the pram and refusing to pass anything but broadcast traffic. Timing couldn't be better - I can run the Unifi Controller needed for setting up the new APs on Frankenvisor.

I've a few changes left to make to the other equipment in the rack, so I'm now thinking ahead to how we get proper structured cabling installed with ethernet ports in all the handy locations.

[drossall]

Unbricked a Western Digital MyBook network backup drive

Along the way, recovered from it the backups of some lost family photos

And replaced the battery in my Nexus 7 tablet. Good weekend for fettling.

Edit: also replaced the charging port, because the same Nexus tablet still wasn't charging fast enough. Seems better now

[davelodwig]

A bunch of MicroTik routerboard and AP hardware into a distributed enterprise grade wireless network in my house.

The ISP supplied wifi couldn't reach the other side of the house, so my solution was to thinly spread tiny poe ceiling mount ap's about the place and centrally manage them from a management box.  Just need to finish the firewall rules now.

D.

[Feanor]

Power outage at Feanor Towers today.

Due to the order in which the servers came back up, one of them was unhappy because the Domain Controller had not come up first, so it was sulking.
It was accepting remote desktop connections, so I remoted into it.

Simply dropping the network connection and then re-enabling it causes the machine to do a fresh round of network initialisation and fixes the problem now that the domain is reachable.

Idiot boy here disables the network adapter *over an RDP session* and wonders why he can't re-enable it again.
Cue rummaging about to find a USB Keyboard and mouse.
Fortunately, there's a VGA cable in place already.

[tiermat]

@Feanor, BTDTGTTS 

[Kim]

Bouns points for doing that on a machine $bignum miles away.

[hulver]

Repaired the broken mysql database that was holding all the library information for my kodi installation. That was a right royal PITA.

[T42]

Got our Club's archiving prog functional again after severe site dislocation following El Prez's discovery of Serif.  I wrote it 12 years ago when I was just finding out about CSS and it's a bit of a mucky shambles, but you wouldn't know it from the outside. Ouf.

[Mr Larrington]

Surplus-to-requirements "120" GB SSD, previously installed in the Grand Hall machine, has now been added to the big bugger in the Estate Office.  Some disassembly was required, notably to get at a free SATA wossname on the motherboard,  But it all went back together successfully and it all works and I've got all these bits¹ left over too

1: Various bits of things that bolt onto other things and would have disks mounted in them if I had disks to spare².
2: Which I do, but CBA to source bits to mount them right now.

[David Martin]

I'm building a set of quiz buttons that run via http through a simple flask app on the lab raspberry pis and some big buttons.

So far I have managed to get things behaving so a web call plays a sound from the Pi, and realised that Flask doesn't maintain state so I have to write a cache class that uses the filesystem or similar to keep things happy. I need to be able to lock it as soon as the first button is pressed.

The cool thing is that it is instantly extendable to a web app that the students can use so we could envisage removing Turning Point clickers for something more functional that could give feedback. Hmm - summer project.

[Mr Larrington]

A corollary of bunging that extra disk into Bruiser McHuge seems to be that the removal of bits of internal disk-mounting bendyware has cured him of his annoying habit of randomly hanging at inopportune moments.  I suspect the bit I removed was making just enough contact with the graphics card to cause intermittent prombles, the said card being a couple of thou longer than the one it replaced.

[David Martin]

A set of quiz buttons.
Dive button by David Martin, on Flickr

Each button is based on a Pi Zero and sends an http request to a controller (Pi 3 with touch screen). We have the Pi anyway for teaching so I may as well use them for something fun. The controller has two buttons. Test mode and game mode/reset. Test mode allows any button to play when pushed. Game mode is first and only button.

I'll expand it over the summer into a proper collaborative on your own device system.

[David Martin]

The buttons were used in anger today. A bit Heath-Robinson in appearance but they worked really well, despite my somewhat Prosecco'd colleagues pounding on them. Even better is that I got espeak to state the names of each group  as the button tone

The final tweaks were to run the buttons with a daemon so they power on and are good to go. Just need to configure each of them at set up with a suitable name (I used REDBUTTON, BLUEBUTTON etc.

The controller (quizmaster) shows me which buttons are pressed and in what order. I should wrap that in a GUI with pygame at some point.

Total cost per button is:

Big red/yellow/green/blue button: £10
Pi zero W: £9
SD card, power supply etc. £10 (approx)
prototype board for Pi Zero: £5
NPN transistor for LED switching 30p
Casing/laser cutting/glue £4

so about £40 per button (unless you can get stuff at a discount)

For the controller I used a Pi 3 with a 7" touch screen and a couple of light up arcade buttons and a second WiFi dongle. Around £120 all in. However, all this kit is reusable for other purposes (and will be as I use the Pi Zero for teaching anyhow).

An easy project and one that is extensible.

[Kim]

So, is it exploitable by a nefarious team flooding the wireless network with data (or just jamming the 2.4GHz band) in the hope of delaying the opposition's HTTP request?