Tuesday, 3 July 2018

Preparing a Raspberry Pi for AWS Greengrass

This article refers to a Raspberry Pi 3 B+. What follows are just some notes taken by me as I progressed through the steps described here:


For details of the process please refer to the document above.

One issue I did encounter was when running the Greengrass dependency checker. On my Raspberry Pi I struggled to get the memory cgroup configured correctly. The solution is included below (see Step 5).

Step 1

Initial setup of the Raspberry Pi and access via SSH was simply a normal setup process. Once connected I needed to start the first steps specific to AWS Greengrass starting with adding users.

Step 2

Basically this is Module 1: Step 9 in the document linked to above.


Step 3

Module 1: item10 calls for an upgrade to the Linux kernel. I chose to ignore this step for now. It will be interesting to see if there are any issues.


The kernel version of my OS was 4.14.50 although the Greengrass instructions suggest 4.9.30.

Step 4

Module 1: item11 is locking down security. No real issues encountered.




Step 5

So now I was at Module 1: item 12 and ready to check dependencies. This was where the only significant issue was encountered. The initial steps all progressed well until I ran the AWS Greengrass dependency checker. This showed an issue with the memory cgroup dependency.




The dependency checker showed the following message regarding a missing required dependency:

1. The ‘memory’ cgroup is not enabled on the device.
Greengrass will fail to set the memory limit of user lambdas.

For details about cgroups refer to the following document (although not specific to Raspian the information should still apply):



Running “cat /proc/cgroups” initially showed that memory subsys_name was not enabled (set to 0). So, I edited the “cmdline.txt” file located in “/boot” with the nano text editor.


I added the following items to the line in that file:

cgroup_memory=1 cgroup_enable=memory

NB: Both cgroup_memory and cgroup_enable were required to make this work.

The total line from my cmdline.txt file ended up looking like this:

dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 cgroup_memory=1 cgroup_enable=memory root=PARTUUID=c20ec4c3-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

I did a reboot and checked /proc/cgroups to see if the change had taken effect. It had with the enabled flag set to 1.


Time to recheck the AWS Greengrass dependencies.


No issues this time.

I did however note the following message:

Note :
1. It looks like the kernel uses ‘systemd’ as the init process. Be sure to set the ‘useSystemd’ field in the file ‘config.json’ to ‘yes’ when configuring Greengrass core.

Note to self: Don’t forget to do that!

This left me ready to install the Greengrass core software:


Sunday, 1 July 2018

Mount a network drive for CrashPlan

I was having issues with getting CrashPlan to backup to network storage (a Western Digital MyBookLive). In short, the drive was not always mapped. I fixed it using advice given in this article:


The batch file looked like this:

net use Z: /DELETE
net use Z: "\\\Andy" "password here" /USER:"username here" >>E:\mount_drive_for_crashplan.log

And I created a scheduled task to run it as instructed in the article.

Friday, 29 June 2018

Installing Plex media server on a Raspberry Pi

This post was covers installing Plex media server on a Raspberry Pi 3 B+ running Raspbian Stretch Lite.

In this case I had already attached an external drive and set up Samba so I could easily add media files to the drive from my Windows PC. See this post for details.

Step 1

Firstly I added a new repository to apt so I could install it using apt-get. To do this I needed to get access to the dev2day.de repository.


First step was to download the key and add it to apt. I switched to be su for this. The commands below show what was run but not any of the resulting output.

sudo su
wget https://dev2day.de/pms/dev2day-pms.gpg.key
apt-key add dev2day-pms.gpg.key

Step 2

Then I created a new sources file for Plex.

cd /etc/apt/sources.list.d
sudo nano plexmediaserver.list

I then added the following line to the file and saved it.

deb https://dev2day.de/pms/ stretch main

Note the version of Raspbian is Stretch. Modify the command for different versions.


Then I updated apt-get so it has the latest package lists.

sudo apt-get update

Step 3

Now I could install Plex.

sudo apt-get install plexmediaserver-installer

Step 4

I wanted to move the Plex database from the SD card storage in the Raspberry Pi to the external drive.

To do that stopped Plex before I moved the Plex library folder from its original location to a new location on the external drive. I then created a symbolic link to in place of the original folder that pointed to the new location. Once that had been done I could restart Plex. Plex would still look for its library in the original location but be redirected by the symbolic link.

sudo service plexmediaserver stop
sudo mv /var/lib/plexmediaserver /media/seagateHDD/plexmediaserver/
sudo service plexmediaserver start


Step 5

Then it was just a case of accessing Plex from a browser on my PC to check it was working. It was! I then started creating new libraries in Plex. The seagateHDD showed up nicely, along with the Media folder containing my video files.

The Plex server was available at


Job done.

Attaching an external hard drive to a Raspberry Pi

This post was covers installing an external USB hard drive to a Raspberry Pi 3 B+ running Raspbian Stretch Lite.

Firstly, I had terrible trouble getting my Seagate Expansion 2 TB USB 3.0 Desktop 3.5 Inch External Hard Drive to work correctly. Endless permission issues, problems with Samba, you name it.

The key to solving these issues was to install the NTFS-3G driver rather than using the standard NTFS driver when mounting the drive. I’ll cover that as I go in the steps described below.

Step 1

I started with the Raspberry Pi shutdown and simply attached the drive to a vacant USB port on the Pi. I the powered up the drive and then the Pi.

Step 2

SSH to the Raspberry Pi as usual. I then ran the following command to see what drives were now attached.

sudo blkid


I looked for the new Seagate drive which in this case was /dev/sda2. I made a note of the information, especially the UUID which I used later.

Step 3

So, I’m skipping all the trial and error here but the next significant thing to do is install the NTFS-3G driver using apt-get.

sudo apt-get install ntfs-3g


Step 4

Time to mount the drive on the file system. I chose to mount the drive under /media rather than /mnt or any other location. So, I created a folder specifically for the drive (/media/seagateHDD) then mounted the drive to that folder.

cd /media
mkdir seagateHDD
sudo mount /dev/sda2 /media/seagateHDD/ -t ntfs-3g

 NB: Note the use of the –t ntfs-3g option.


This proved the drive could be mounted and that it worked. As you can see permissions are wide open.

Step 5

Now we need to set up the system to reconnect the drive at start-up. For this I modified the fstab file.

sudo nano /etc/fstab


And added the following line. Note the use of the UUID rather than /dev/sda2. This helps to ensure the same drive gets reattached just in case the device changes.

UUID=FC82A10F82A0D006 /media/seagateHDD ntfs-3g defaults 0 0


Step 6

Time to install Samba. Firstly I installed Samba using apt-get.

sudo apt-get install samba samba-common-bin


When that was done I edited the samba configuration file.

sudo nano /etc/samba/smb.conf

And added the following section.

     writeable = yes
     public = yes
     directory mode = 0777
     path = /media/seagateHDD/Media
     comment = Pi shared media folder
     create mode = 0777

Note that there was an existing folder called Media on the drive. I chose to make that folder accessible via Samba.


The a quick restart of Samba to read the new configuration.

sudo /etc/init.d/samba restart

Step 7

Test from Windows. I just added a Media Location mapped to my Raspberry Pi’s IP address and the media share and that was it!

Tuesday, 26 June 2018

Quick headless setup of a Raspberry Pi 3

Here are the steps taken to get a Raspberry Pi 3 B+ up-and-running on my home network but doing so headless – no monitor etc. attached.

Step 1

Follow the basic installation guide from raspberrypi.org to flash a micro SD card. I used the Rasbian Stretch Lite image and Etcher to flash the image onto the SD card.


Step 2

Create a file called ssh (no file extension) in the root of the newly created boot SD card.  This enables SSH when the Raspberry Pi starts up.

The file doesn’t need any contents. Just the presence of the file enables SSH connections to the Pi.

Step 3

Put the SD card in the Raspberry Pi, connect it to the network via ethernet and power it up.

Step 4

Access to your router management console and find the Raspberry Pi as a connected device. Note down the IP address.

If you can, use DHCP management tools to reserve the IP address so it won’t change (this makes it easier to reconnect to the Pi if you have to bounce your router).

Step 5

Use Putty or similar tool to SSH on to the Pi using the IP address from Step 4. Login as the ‘pi’ user (default password is ‘raspberry’ with no quotes).


Step 6

Run the following command:

sudo raspi-config

This fires up the Rasperry Pi configuration tool. Make any changes you want to (e.g. enabling wi-fi or changing the host name). Change the default password if nothing else.


Step 7

Run the following command:

sudo apt-get update

And then this one:

sudo apt-get upgrade

You’re done. Raspberry Pi is up-and-running.

Thursday, 1 March 2018

Suspicious Windows 10 Printer Update?

I’ve been seeing this in my Windows 10 update after receiving a notification that it failed to install:

Canon - Printer - 4/21/2000 12:00:00 AM - 10.0.17046.1000
Status: Awaiting install


It seems I’m not alone in spotting this rather odd and somewhat suspicious issue:


For now I am trying the “Show or hide updates” troubleshooter package from Microsoft which you can find here:

Monday, 27 November 2017

Elements of the Archimate 3.0 Application Layer

This post is a basic aide-memoire for me to remember the characteristics of the Archimate Application Layer model elements. For a detailed description refer to the main Archimate 3.0 documentation.

The model elements are divided into 3 categories:

  • Active Structure
  • Passive Structure
  • Behaviour

Active Structure






Encapsulation of application functionality aligned to implementation structure

Modular and replaceable

Encapsulates behaviour and data

Exposes services and makes them available through interfaces

A self-contained unit

Independently deployable, re-usable, and replaceable

Performs one or more application functions

Functionality is only accessible through application interfaces



An aggregate of two or more application components that work together to perform collective application behaviour

Specifies which components cooperate to perform some task

A logical or temporary collaboration of application components

Does not exist as a separate entity



A point of access where application services are made available

How the functionality of a component can be accessed

Exposes application services

The same interface may expose multiple services








Automated behaviour performed by a component

Describes internal behaviour of a component

Functions are exposed externally through one or more services

May access data objects



A unit of collective application behaviour performed by two or more application components

Collective behaviour performed by components that participate in a collaboration



A sequence of application behaviours that achieves a specific outcome

The internal behaviour performed by a component to realize a set of services

May realize application services

May access data objects

A component may perform the process



Denotes a state change

Does not have a duration

May be internal or external

May have a time attribute



An explicitly defined exposed application behaviour

Functionality is exposed through interfaces

Realised by one or more functions

Provides a useful unit of behaviour


Passive Structure






Data structured for automated processing

A self-contained piece of information

Clear business meaning