Saturday, 4 August 2018

How to send files to a Raspberry Pi from Windows 10

This post refers to a Raspberry Pi 3b+ running Raspbian Stretch.

A quick note; I’m going to use the PuTTy Secure Copy client (PSCP) because I have the PuTTy tools installed on my Windows machine.

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In this example I want to copy a file to the Raspberry Pi home directory from my Windows machine. Here’s the command format to run:

pscp -pw pi-password-here filename-here pi@pi-ip-address-here:/home/pi

Replace the following with the appropriate values:

  • pi-password-here with the Pi user password
  • filename-here with the name of the file to copy
  • pi-ip-address-here with the IP address of the Raspberry Pi


The following example includes the –r option to copy over a directory – actually a Plex plugin – rather than a single file to the Pi.

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How to check that AWS Greengrass is running on a Raspberry Pi

This post refers to a Raspberry Pi 3 B+ running Raspbian Stretch.

To check that AWS Greengrass is running on the device run the following command:

ps aux | grep -E 'greengrass.*daemon'

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A quick reminder of Linux commands.

The ps command displays status information about active processes. The ‘aux’ options are as follows:

a = show status information for all processes that any terminal controls
u = display user-oriented status information
x = include information about processes with no controlling terminal (e.g. daemons)

The grep command searches for patterns in files. The –E option indicates that the given PATTERN – ‘greengrass.*daemon’ in this case - is an extended regular expression (ERE).

Friday, 3 August 2018

Automatically starting AWS Greengrass on a Raspberry Pi on system boot

This post covers the steps necessary to get AWS Greengrass to start at system boot on a Raspberry Pi 3+ running Raspbian Stretch. The Greengrass software was at version 1.6.0.

I don’t cover the Greengrass installation or configuration process here. It is assumed that has already been done. Refer to this tutorial for details.

What we are going to do here is use systemd to run Greengrass on system boot.

Step 1

Navigate to the systemd/system folder on the Raspberry Pi.

cd /etc/systemd/system/

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Step 2

Create a file called greengrass.service in the systemd/system folder using the nano text editor.

sudo nano greengrass.service

Copy in to the file the contents described in this document.

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Save the file.

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Step 3

Change the permissions on the file so they are executable by root.

sudo chmod u+rwx /etc/systemd/system/greengrass.service

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Step 4

Enable the service.

sudo systemctl enable greengrass

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Step 5

You can now start the Greengrass service.

sudo systemctl start greengrass

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You can check that Greengrass is running.

ps –ef | grep green

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Reboot the system and check that Greengrass started after a reboot.

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Friday, 3 August 2018

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:

https://docs.aws.amazon.com/greengrass/latest/developerguide/module1.html

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.

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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.

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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.

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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.

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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):

https://sysadmincasts.com/episodes/14-introduction-to-linux-control-groups-cgroups

Solution

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.

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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.

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Time to recheck the AWS Greengrass dependencies.

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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:

https://docs.aws.amazon.com/greengrass/latest/developerguide/module2.html

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:

https://support.code42.com/CrashPlan/4/Backup/Back_up_files_from_a_Windows_network_drive

The batch file looked like this:

net use Z: /DELETE
net use Z: "\\192.168.0.13\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.

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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
exit

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.

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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


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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 http://192.168.0.20:32400/web/.

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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


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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


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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.

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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


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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


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Step 6

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

sudo apt-get install samba samba-common-bin


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When that was done I edited the samba configuration file.

sudo nano /etc/samba/smb.conf

And added the following section.

[media]
     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.

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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!