How To: Permanently Display line numbers for Vim or Vi

It can be very useful when troubleshooting to display line numbers in Vim or Vi. To enable this in your ~/.vimrc file add :

:set number

which can also be manually set within Vim or Vi. Within the editor to remove the line numbers :

:set nonumber

VirtualBox slow on installation of Guest OS

I use VirtualBox for testing in many environments. Normally the defaults are fine for installing Linux but on one environment it was really slow to just install. Installing Debian Jessie from an ISO would normally take 15 minutes but in this environment after an hour it was still only at 35%. The host OS was not over taxed and has lots of spare CPU + RAM resources free.

After some testing I found the issue was resolved by :

1. Open Settings
2. Navigate to System->Motherboard
3. Change the Chipset to ICH9 (see below)
4. Press OK

Now the installation will be fast.

Change docker default storage location

One of the first tasks I wanted to do after installing Docker on Arch Linux was to be change the default partition storage location. The default location is /var/lib/docker which is the path docker uses as the root of the docker runtime.

Looking at the man pages for docker its not amazingly obvious at first which option needs to be configured but after some research I found it is :

-g, --graph=""

And the service status shows this option is not set by default

$ sudo systemctl status docker
* docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2015-09-07 13:07:10 PDT; 2h 0min ago
     Docs: https://docs.docker.com
 Main PID: 420 (docker)
   CGroup: /system.slice/docker.service
           `-420 /usr/bin/docker daemon -H fd://
Its possible to define --graph within the /usr/lib/systemd/system/docker.service file but this will be overwritten with every new release of docker.

The solution is first create a directory:

$ sudo mkdir /etc/systemd/system/docker.service.d

Then create a file similar to the following

$ cat /etc/systemd/system/docker.service.d/dockerruntimeroot.conf
[Service]
ExecStart=
ExecStart=/usr/bin/docker daemon -H fd:// --graph /mnt/docker-data

Then

$ sudo systemctl daemon-reload
$ sudo systemctl restart docker

Now the new path will be shown in the service status

$ systemctl status docker
* docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
  Drop-In: /etc/systemd/system/docker.service.d
           `-dockerruntimeroot.conf
   Active: active (running) since Mon 2015-09-07 15:52:28 PDT; 1min 49s ago
     Docs: https://docs.docker.com
 Main PID: 8981 (docker)
   CGroup: /system.slice/docker.service
           `-8981 /usr/bin/docker daemon -H fd:// --graph /mnt/docker-data

Monitor and Display Apartment Temperature using BeagleBone Black

As a project I wanted to be able to monitor the temperature in my apartment and display it on an LCD screen. I also decided that I would also like to simultaneously display the local city temperature.

Setup

In addition to the BeagleBone Black I purchased from AdaFruit

• MCP9808 High Accuracy I2C Temperature Sensor Breakout Board

• RGB backlight negative LCD 16x2

AdaFruit provide two Python libraries

• MCP9808
• CharLCD

For the OS I am running the latest version of Debian wheezy

# lsb_release -a

No LSB modules are available.

Distributor ID: Debian

Description: Debian GNU/Linux 7.7 (wheezy)

Release: 7.7

Codename: wheezy

After following the wiring instructions from Adafruit and installing the two python libraries as mentioned above I could display the temperature from my Apartment on the LCD screen. The next step was to get the local temperature in Vancouver, Canada. I looked at a few options such as screen scraping using the Python Beautiful Soup library on the Environment Canada website. The screen scraping did work but not consistently. Looking around for some other options I found the fantastic OpenWeatherMap project, which for Canada uses Environment Canada as a data source. There is a Python library pyowm for OpenWeatherMap. This can be installed using pip :

# pip install pyown

From OpenWeatherMap you can register for free and obtain an API key. Using the pyowm library is relatively straight forward which then allows the data to be obtained and displayed on the LCD screen. 

I have a cron job that runs every 15 minutes during the hours I want the screen to display. I posted the Python script I used on my GitHub repository in case anyone finds it a useful reference.

Fix : Linux NTFS Error Mounting $MFTMirr does not match $MFT (record 0)

With an external USB hard drive that is used to share files between Windows and Linux computers you may get an Error on Linux similar to the following :

Error mounting: mount exited with exit code 13: $MFTMirr does not match $MFT (record 0). Failed to mount ‘/dev/sdd1′: Input/output error NTFS is either inconsistent, or there is a hardware fault, or it’s a SoftRAID/FakeRAID hardware. In the first case run chkdsk /f on Windows then reboot into Windows twice. The usage of the /f parameter is very important! If the device is a SoftRAID/FakeRAID then first activate it and mount a different device under the /dev/mapper/ directory

To resolve the issue is to use ntfsprogs which can be installed from most Linux distributions e.g.

Arch Linux

$ sudo pacman -S ntfsprogs

Ubuntu/Linux Mint/Debian

$ sudo apt-get install ntfsprogs

To fix the issue run the following command syntax

$ sudo ntfsfix <drive mount point>

Change the drive to be the same shown in the Error. For example in the above error the command is

$ sudo ntfsfix /dev/sdd1

How to : Disable BeagleBone USR Heartbeat LED lights

The BeagleBone Black by default has 4 User LED's USR0, USR1, USR2 and USR3 that light up to show the board is alive. While useful it can be annoying.

There are 4 sub directories under /sys/class/leds which allow you to configure the LED behaviour. There is one directory per LED. Within each sub directory a trigger file details what triggers the LED e.g.

# cat /sys/class/leds/beaglebone\:green\:usr0/trigger

none nand-disk mmc0 mmc1 timer oneshot [heartbeat] backlight gpio cpu0 default-on transient

The [heartbeat] is what is showing the board is alive. This can be disabled via :

# echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger

# echo none > /sys/class/leds/beaglebone\:green\:usr1/trigger

# echo none > /sys/class/leds/beaglebone\:green\:usr2/trigger

# echo none > /sys/class/leds/beaglebone\:green\:usr3/trigger

To light up the LED use the brightness file.

Turn USR0 on

# echo 1 > /sys/class/leds/beaglebone\:green\:usr0/brightness

Turn USR0 off

# echo 0 > /sys/class/leds/beaglebone\:green\:usr0/brightness

Reboot

The LEDs will be reset on after reboot which is useful for troubleshooting. The /sys directory on Linux is a RAM based File system. For ease you could create a simple bash script to run as the last file on boot.

# cat DisableUSRLEDs.sh

#!/bin/bash

echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger

echo none > /sys/class/leds/beaglebone\:green\:usr1/trigger

echo none > /sys/class/leds/beaglebone\:green\:usr2/trigger

echo none > /sys/class/leds/beaglebone\:green\:usr3/trigger

BeagleBone Black Debian image initial steps

This article details initial steps of a BeagleBone Black with a Debian image. For this setup I am using a 5V adapter for power and connecting the Ethernet port to my local LAN.

• With power and Ethernet connected the BeagleBone is set to automatically run DHCP. You can ping the hostname of 'beaglebone' to show the connectivity

$ ping beaglebone

PING beaglebone.lan (192.168.1.155) 56(84) bytes of data.

64 bytes from beaglebone.lan (192.168.1.155): icmp_seq=1 ttl=64 time=0.964 ms

64 bytes from beaglebone.lan (192.168.1.155): icmp_seq=2 ttl=64 time=0.630 ms

• Next ssh as root (there is no password set)

$ ssh root@beaglebone

• Set a password for root :

# passwd

• Update to the latest builds

# apt-get update
# apt-get upgrade

• Set the correct Timezone

# dpkg-reconfigure tzdata

• Confirm correct date

# date

• Check that the web server is listening on port 80

# netstat -an | grep -i 80

tcp6 0 0 :::8080 :::* LISTEN

tcp6 0 0 :::80 :::* LISTEN

• In a web browser (not IE) open the IP address of your Beaglebone to display the default page
• Enjoy your Beaglebone!