Category Archives: tech

All things technical

Species List (First Attempt)

yes, after 10+ years living in Durham it’s about time I had a stab at this. There’s a couple of things I want to do on the garden:

  1. Species List
  2. Map

And whenever I start thinking about it I overthink it about all the things I’d like to note, plot, monitor. And in the end, I do nothing.

So let’s make a start:

Hang on, where’s my Tablepress plugin gone? It should be here? I’ve just installed it. Back in a tick.

Permissions on /dev/video0 running motion on Raspberry pi

It pretty much happens that every time I setup motion on a new build that it doesn’t work right away. There’s usually a few things I miss. Usually it’s an error reading from the camera, the logs reporting something like:

Feb 17 10:51:21 pi2 motion: [1] [NTC] [ALL] motion_init: Thread 1 started , motion detection Enabled
Feb 17 10:51:21 pi2 motion: [1] [NTC] [VID] vid_v4lx_start: Using videodevice /dev/video0 and input -1
Feb 17 10:51:21 pi2 motion: [1] [ALR] [VID] vid_v4lx_start: Failed to open video device /dev/video0:

which invariably means the camera is broken or I’ve misconfigured my motion setup.

This one was puzzling me a little though. It’s on a raspberry pi, imaginatively titled pi2, and it was failing to read from the camera. The reason I was puzzled was that the hardware combination had worked before. What had gone wrong was the micro-SD card, and I’d done a new raspbian build, copying over the relevant motion configuration files from the old card.

Clearly the difference had to be something to do with the OS. So what was different? I’d taken the opportunity of the SD failure to download and install the latest version of raspbian and everything looked good to go.

Running motion as root worked fine, both against the vanilla configuration file, and the customised config file I wanted to use. So let’s have a look at the video file:

root@pi2:~# ls -l /dev/video0
crw-rw----+ 1 root video 81, 0 Feb 17 11:17 /dev/video0

Looks about right. Ah, the video group. I need to be in the video group. That might be it:

root@pi2:~# usermod -G video dougie

Restart motion and try again. Nope. Let’s have a closer look at that file.

On pi2 (with a new version of raspbian):

crw-rw----+ 1 root video 81, 0 Feb 17 11:17 /dev/video0

and on pi1 (another rpi, running motion fine, with a slightly older version of raspbian):

dougie@pi1:~ $ ls -l /dev/video0
crw-rw---- 1 root video 81, 0 Jan 8 22:54 /dev/video0

Very similar, but not identical. The newer version of the device file has and extra + at the end of the permissions bit, which means the file has extra security permissions set. I’ve not had cause to use Access Control Lists (ACLs) before, and it was a temptation just to chmod 777 on the file as a quick and dirty, and lazy, fix, but I thought it’d be better to take a closer look. Using the getfacl command:

root@pi2:~# getfacl /dev/video0
getfacl: Removing leading '/' from absolute path names
# file: dev/video0
# owner: root
# group: video
user::rw-
user:pi:rw-
group::rw-
mask::rw-
other::---

I could see that I (me: dougie) did not appear on the list, although the default rpi user pi does. I rarely use the pi account. One of the first things I do is change its password, create my own user, and use that instead. So it looks like the default install for raspbian allows user pi to access /dev/video0. It also looks like I can’t access the file, despite being a member of the group video.

I found a good command summary on the centos documentation website, and using that gave myself access:

root@pi2:~# setfacl -m u:dougie:rw /dev/video0

That did the trick.

 

 

Trackr Bravo battery life

The TrackR does many things badly. The Tile just does one thing well.

Another email from Trackr – this time about their new Battery Program. This is about a wizard wheeze where you can pay Trackr for replacement batteries.

Reading on in their email there’s a section subtitled:

What if every time your battery was dead, you had to buy a brand new device?

Well, what indeed. One wonders what can they be alluding to? I wonder if it’s another well known Bluetooth tracking device that has to be replaced about once a year when the battery nears end of life?

The TrackR Bravo is a slick, elegant looking device, and looks better than the Tile. But having bought a handful of both devices as soon as they hit the market, the Tile is the winner by a mile. On reliability, build quality, and Customer Service the Tile is the winner. My experience of using Trackr has been one of interminable irritability. I’ve tried its various features and abandoned them finding them gimmicky, unreliable and pointless. I’m struggling to think of any redeeming features, and the closest I can get is that the Bravo looks ok.

Trying a different brand of battery

I’ve just replaced the batteries in all my Trackr Bravos. The ones I’ve removed were brand new Maxells. Perhaps I was unlucky. I thought Maxell were a pretty good brand. This time I’m replacing them with GP batteries. I only found the batteries were dead by accident, as I thought I get more than 3 months out of the Maxells. It didn’t occur to me to check connectivity every day, and on the TrackR app (unlike the Tileapp), you need to check each TrackR individually – whereas with Tile you can scan all your tiles’ status in one glance.

I’ve had Tile and TrackR since they became available in the UK – and have been running them head to head since I bought them. It’s a very unequal contest. Give me the Tile any day.

TrackR Tile Head to Head

malware requesting Read Receipt

Another day, another slew of malware and spam. But I don’t recall one like this before.

The obvious signs are there, such as impersonal salutation and dubious attachment. The part that interested me was the request for a read receipt. Here’s a screenshot of the email:

2015-10-21_11-16-17

If you weren’t looking closely at the read receipt request you’d be forgiven for thinking it was the same as the (apparent) sender. But it’s actually an Australian domain.

2015-10-21_11-16-17

A good reason for not automating read (or delivery) notifications.

 

 

Outlook webmail won’t let you login if password renewal is due

which sorta makes sense.

But in Exchange 2013 it’s possible to change your password in OWA without logging into AD so if a user is scheduled to change their password the next time they login, I thought OWA might force a password change. Actually, thinking about that, how would that work? It would have to automatically present the change password dialogue. Perhaps that’s not possible.

Just need to remember that for users who don’t log into AD directly on a PC, but just use OWA all the time, forcing them to change their password on next login won’t work.

Web searches don’t reveal much, but if I understand Change Password Feature in Outlook Web App correctly, it’s WAD.

what a mess

What’s happened here is that I’ve had two poorly maintained blogs and I’ve crudely welded them together into one.

This blog is now a messy tramsmash of www.bluecedar.org.uk and katsura.org.uk.

The basics were simple enough:

  1. Create new self-installed WordPress blog (this one)
  2. Export everything out of bluecedar.org.uk (Tools/Export)
  3. Export everything out of katsura.org.uk (Tools/Export)
  4. Import into katsura.uk (Tools/Import)

Step 4. required installing a plug-in but that was no big deal.

It’s a mess, but it’s a nice mess.

Find Willow’s Collar

What a difference a day makes.

Yesterday I was wondering on whether it’s possible to set up a dumb ‘slave’ iPhone to act as a part of the hive mind and pass on location info about our cats. Today Willow has wandered in, sans collar, and that means no tile either. I haven’t lost my cat, but I have lost his collar.

I’ve marked Willow’s Collar as Lost. I’ve wandered round the garden and the street staring at my iPhone at the slowly rotating grey circle. Nothing yet.

Let the games begin …

my Tiles have arrived

So almost a year after first placing my order my tiles have finally arrived.

the tiles have arrivedFirst impressions? Quite similar to others – they’re bigger than I expected, but light too. When attached to the cats’ collars the tiles can look a little oversized although this seems to bother me more than it bothers them.

The tile uses bluetootRosie showing off her new tileh and as such its range is nothing amazing. I’ve dabbled with bluetooth location devices and know that the “works up to …” type claims need to be treated with some skepticism. So with realistic expectations I was unsurprised to find that I was lucky if detection would work from one end of the house or garden to the other, especially if there’s a brick wall or tree in the way.

The most intriguing aspWillow with new tile on his collarect of the tile concept for me is the idea of the hive mind. Anyone else who has the tileapp installed on their iPhone or iPad should (in theory) be picking up my tiles if they’re in range of that person’s IOS device. This begs the rather interesting question, how many tiles are there in Durham? Given that mine have just arrived and I ordered mine pretty early on, I wouldn’t be surprised if the answer is close to zero. Especially as a fundamental part of the design philosophy is that you don’t know if you’re picking up someone else’s tiles and passing the location info on.

I ordered 8 tiles, a decision partly based on cost, and partly because the tileapp can only register 8 tiles to an account. I’m not sure how that works if you want some more tiles. Perhaps you have to set up multiple accounts. Eight tiles is a nice number. That’s one for each cat, keys, wallet and one or two to experiment with.

However the main problem I’m having with my shiny new tiles is connected to a pretty irritating limitation regarding the amount of accounts that can be registered to a particular tile. Bluetooth only allows one IOS device to be connected to a tile (or any other bluetooth peripheral for that matter) at any one time. Tile explain this in an FAQ and there’s some promising sounding developments about sharing devices in the pipeline.

No matter I thought – I have a spare iPhone after upgrading to the iPhone 5S. My old iphone 4S is still working fine so I decided to install the tileapp on that too and join the Hive Mind. It doesn’t seem to be possible to do much in the app without creating an account but no problem. I created another account with no tiles registered (although it keeps bugging me to do this). I think of this as a slave account. As far as I understand it anyone with an iPhone or iPad should if they wished be able to install the app and act as a sort of volunteer conduit of tile locations. I’ve tried this and it doesn’t work. In theory my iPhone 4S should sit quietly at home and covertly collect tile location info and pass it on the the hive mind. But it’s not working.

Tileapp screenshot

This is a snapshot of the app driving home after an overnight stay away. According to this screenshot the three cats, Rosie, Willow and Mr Mittens have been out of range for around a day. This isn’t the case: they are at home within bluetooth range of an iPhone 4S logged into a tile account.

Logging the iphone into the ‘live’ account sorts things out and the iPhone 4S at home faithfully notes the ‘last seen’ location of the various felines so the handset is working, as is my iPad. Which rather begs the question – if someone else is running the tileapp on their iPhone on their account – will it pick up my tiles and pass the information on? I suspect it may not and I can’t think of a way of testing this apart from what I’ve been doing, which would strongly suggest it doesn’t work. I emailed support via the tile website a few days ago, nothing back yet.