Install and Configure Go/Golang on Raspberry Pi

Go/Golang is one of the hot programming languages while I’m typing this today.

Go is a programming language created at Google in 2009 by Robert Griesemer, Rob Pike and Ken Thompson. Go is a statically typed compiled, procedural language similar to C, with memory safety, garbage collection, structural typing, concurrency and other great features are bundled to make it better compared to other languages in the marketplace.

Docker, Kubernetes, Graphana, Hugo are some of the best apps written in Go. It has a robust set of libraries and app performance is better compared to other languages.

Today I’m starting my journey to learn Go/Golang and Google will be my mentor to install and setup Golang on my Raspbian OS/Raspberry Pi 3. To get the latest version use below steps instead of native package management tool such as apt.

Installation Steps:

  • Download the current stable version of Go available on the google’s official website. At the time of writing this tutorial, 1.12.4 is the stable version. Check the latest version here
cd ~ && curl -O https://dl.google.com/go/go1.12.4.linux-armv6l.tar.gz

Above command would change directory to your ‘Home’ directory and download Go compressed tar file using ‘Curl’

  • Extract compressed tar file and place it inside /usr/local directory. Please note root level access or sudo access required to perform this step.
sudo tar -C /usr/local -xzvf go1.12.4.linux-armv6l.tar.gz
  • Set Path variables to avoid typing complete path and in order to access binaries or libraries of Go by the Raspbian OS. Open ~/.profile, a hidden file located in your ‘Home’ directory. Use nano or vi or subl to edit the file (subl ~/.profile). Add below lines at the end of the file.
export GOPATH=$HOME/go
export PATH=$PATH:/usr/local/go/bin:$GOPATH/bin
  • To take effect of the above changes made to the file ‘profile’, run the below command. The source command can be used to load any functions file into the current shell, script or a command prompt.
source ~/.profile
  • Create directory called ‘go’ in the ‘Home’ directory. All my codes are placed in the folder. Change the directory name as per choice but do change the GOPATH accordingly as mentioned above.
 mkdir $HOME/go 
  • Validate Go is working as expected or not by running below command
vb@pi:~ $  go version
go version go1.12.4 linux/arm
vb@pi:~ $

My first code in Go

Create a directory first_code in ‘go’ and write following content in the file and save it as first_code.go

mkdir -p $HOME/go/src/first_code 
{-p is used to create directory and its sub-directories at once}
package main

import "fmt"

func main() {
    fmt.Printf("My first code in Go Language!!!\n")
}

Now build and run the code. Change directory
to the first_code cd ~/go/src/first_code and run below commands

vb@pi:~/go/src/first_code $ go build
vb@pi:~/go/src/first_code $

vb@pi:~/go/src/first_code $ ./first_code
My first code in Go Language!!!
vb@pi:~/go/src/first_code $

Note:

Above steps are applicable to any Linux distributions just by changing the first step of downloading the compressed tar file. Change the architecture from arm6l to amd64 or as applicable to your hardware.

I am able to successfully setup GO on my Pi. Hope you’d also do the same and happy learning Go. If you have any issues or questions please mention them in the below comment section.

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Docker’ize’ Python

What is Docker?

Docker is a computer program that performs operating-system-level virtualization, also known as “containerization”. It was first released in 2013 and is developed by Docker, Inc. source: Wikipedia

How Docker works?

Docker containers wrap up software and its dependencies into a standardized unit for software development that includes everything it needs to run: code, runtime, system tools, and libraries. This guarantees that your application will always run the same and makes collaboration as simple as sharing a container image.
source: www.docker.com

Why Docker?

Docker unlocks the potential of your organization by giving developers and IT the freedom to build, manage and secure business-critical applications without the fear of technology or infrastructure lock-in. source: www.docker.com

Pycodestyle @ Sublime Text

Is your script/code looks dull and not in order? If yes, then its time to use pycodestyle!!

Pycodestyle (formerly known as PEP8) is a syntax and style checker tool for Python language. In this blog, I’ve documented step by step procedure to install this with Sublime Text.

Before we start, let us briefly understand more about linter. Lint or linter is a tool that analyzes source code to flag programming errors, bugs, stylistic errors. To know more please check out the wiki link

Pycodestyle is one of the linter plugins available for Sublime Text. To install this plugin, first, we need to install Sublime Linter plugin.

Prerequisites:

  1. Python3.x
  2. Sublime Text
  3. PIP

***This step by step procedure to apply to Debian and Debian based Linux Operation Systems.***

Steps to install pycodestyle:

  1. Install system package using pip or apt
$pip3 install pycodestyle
OR
$sudo apt install python3-pycodestyle
$which pycodestyle # shows the location where pycode style is

2. Install pycodestyle plugin in sublime text

a. Open package control (CTRL+SHIFT+P), type 'install package' and hit 'ENTER' # It takes some time to load repositories. 
b. Type 'sublimelinter-pycodestyle' and Click on the first option as shown below. After installation, a new tab window will open showing installed plugin information
C. To configure sublime-linter settings, goto Preferences > Package Settings > SublimeLinter > Settings
d. In the Sublime Linter settings, make sure @disable: false is set s shown in below screenshot. 
e. To test pycodestyle, create a new file and save it as test.py.
Start writing the code, Pycodestyle will automatically start showing the errors while you are typing in the console message.

That’s it!! Your code looks more disciplined of course after fixing the errors 🙂

In addition to pycodestyle, try pylint, pyflakes and pydocstyle plugins as shown above. These plugins improve Code Quality by following Python Coding Standards. Following best practices will make you a good scripter/developer and remember Quality Matters!!

References:

  1. https://pypi.org/project/pycodestyle/
  2. https://github.com/ergdev/SublimeLinter-pycodestyle
  3. http://pycodestyle.pycqa.org/en/latest/
  4. http://www.sublimelinter.com/en/stable/settings.html

So go ahead and use pycodestyle. Use the above references to deep dive and learn more about this plugin which is a ‘Must Have’ for the Sublime Text. Happy Pythonic way of coding!!

Python’s sh Library

Wish you all Happy, Prosperous & Pythonic New Year 2019!!

I thank everyone for stopping by my blog for 15K times in 2018 which is the highest so far! 

“Looking back at my life’s voyage, I can only say that it has been a good trip.” ~ Ginger Rogers

Similar to the above quote, I’d started my scripting voyage by writing shell, batch and Perl scripts in good old days. I miss some of the awesome, builtin & yet simple to use features available in shell. I felt using those features or builtins would make my life easier while writing scripts in Python…

Besides that, one main reason to look back at the past was while imparting the Python Workshop at my office. One of the participants raised concerns over Python’s builtin modules like OS and Subprocess. They mentioned we can accomplish with very simple steps in ‘Shell’ instead of using OS or Subprocess module. I had to accept the fact that sometimes Python is not so easy as we think!

After googling for a while I finally found this… Say hola to ‘sh‘ Module!

The ‘sh’ library provides simple and intuitive alternative to OS/System/Subprocess modules.

‘sh’ module simplifies Python’s ability to interact with native OS by calling shell commands. This would greatly helps in automation of routine tasks and running sequence of commands, parsing output as per requirement.

Python is a powerful language powered by those great developers who are continuously contributing to enable new features every day in day out. I would like to thank Andrew Moffat for the ‘sh’ library. This library is one of my favourites.

To install this library using PIP, run below command

pip3 install sh 

Please find sample scripts output. 

>>> import sh

>>> sh.uname()

Darwin

>>> sh.uptime()

 7:13  up 11 days, 23:29, 4 users, load averages: 1.51 1.65 1.88

>>> 

>>> sh.echo(‘Hello, This is shell\’s echo running from Python’)

Hello, This is shell's echo running from Python

>>> sh.who()

vinay    console  Dec 21 07:45 

vinay    ttys000  Dec 21 07:46 

vinay    ttys001  Dec 21 07:46 

vinay    ttys003  Jan  2 07:02 

>>>sh.df()

Filesystem    512-blocks     Used Available Capacity iused               ifree %iused  Mounted on

/dev/disk1s1   236568496 96124200 131754736    43% 1042911 9223372036853732896    0%   /

devfs                376      376         0   100%     653                   0  100%   /dev

/dev/disk1s4   236568496  6291496 131754736     5%       3 9223372036854775804    0%   /private/var/vm

map -hosts             0        0         0   100%       0                   0  100%   /net

map auto_home          0        0         0   100%       0                   0  100%   /home

>>> sh.ifconfig()

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384

options=1203<RXCSUM,TXCSUM,TXSTATUS,SW_TIMESTAMP>

inet 127.0.0.1 netmask 0xff000000 

inet6 ::1 prefixlen 128 

inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 

nd6 options=201<PERFORMNUD,DAD>

gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280

stf0: flags=0<> mtu 1280

XHC20: flags=0<> mtu 0

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500

ether b8:e8:56:36:0b:58 

inet6 fe80::149c:1b88:578c:73f8%en0 prefixlen 64 secured scopeid 0x5 

inet 192.168.1.9 netmask 0xffffff00 broadcast 192.168.1.255

nd6 options=201<PERFORMNUD,DAD>

media: autoselect

status: active

p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304

ether 0a:e8:56:36:0b:58 

media: autoselect

status: inactive

awdl0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1484

ether 8a:0c:61:9e:64:9b 

inet6 fe80::880c:61ff:fe9e:649b%awdl0 prefixlen 64 scopeid 0x7 

nd6 options=201<PERFORMNUD,DAD>

media: autoselect

status: active

en1: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500

options=60<TSO4,TSO6>

ether 72:00:00:20:b1:90 

media: autoselect <full-duplex>

status: inactive

en2: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500

options=60<TSO4,TSO6>

ether 72:00:00:20:b1:91 

media: autoselect <full-duplex>

status: inactive

bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500

options=63<RXCSUM,TXCSUM,TSO4,TSO6>

ether 72:00:00:20:b1:90 

Configuration:

id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0

maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200

root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0

ipfilter disabled flags 0x2

member: en1 flags=3<LEARNING,DISCOVER>

        ifmaxaddr 0 port 8 priority 0 path cost 0

member: en2 flags=3<LEARNING,DISCOVER>

        ifmaxaddr 0 port 9 priority 0 path cost 0

nd6 options=201<PERFORMNUD,DAD>

media: <unknown type>

status: inactive

utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 2000

inet6 fe80::bd0:9dea:48de:5645%utun0 prefixlen 64 scopeid 0xb 

nd6 options=201<PERFORMNUD,DAD>

>>> 

Thanks for stopping by, please share your comments and ideas to improve this blog. Keep watching for more Python libraries used for automation.

Telnet (NetCat) and Ping Script

Nowadays most of the Linux distros do not include Telnet. If needed we can install it using the usual methods.

Let’s embrace Netcat which is a best alternative to Telnet. Earlier I had written a Perl script which did Telnet and Ping checks across multiple hosts.

This script requires two input files ips.csv and ports.csv. As the name suggest all target host IP’s to be placed in ips.csv file and the ports to which to netcat is placed in ports.csv. Output is in HTML format and user receives an email with colour coded results.

Replace ips.csv & ports.csv file contents and change SMTP IP and email address.

Here is the Python script which replaces Telnet with Netcat.

SSH Keys – Password less authentication

I was trying to setup SSH Keys between two different flavors of Linux Host by following this Howto

I did run commands exactly as per mentioned in the how to; but it didn’t work. Error message as under

vin@CLIENT:~$ ssh vsa@192.0.0.10
vin@192.0.0.10’s password:
Last login: Mon May 22 10:45:03 2017 from 192.0.0.10
-bash: id: command not found
-bash: id: command not found
-bash: id: command not found
-bash: tty: command not found
-bash: uname: command not found

After googling and trail and error method finally found a fix.

Instead of Step 3 as per the above How to, use the below commands.

  1. Ensure on the server proper permissions set on the .ssh folder if not set permissions as

$chmod -R 775 .ssh (.ssh is located in user home directory e.g: /home/vin)

  1. Run this command to copy the Key file from client to server

$cat ~/.ssh/id_rsa.pub | ssh vin@192.0.0.10 ‘umask 0077; /bin/mkdir -p .ssh; /bin/cat >> .ssh/authorized_keys && echo “Done!”‘

After running above command, server 192.0.0.10 do not ask for password when user vin try to login.

vin@CLIENT:~$ ssh vin@192.0.0.10
Last login: Mon May 22 11:54:29 2017 from 192.0.0.10
[vin@SERVER ~]$

Manage services from CLI on Linux

In Window$ OS, we can check running services and its status by going to Services console. (Start > Run > services.exe)

Similarly, to access running services info and status under Linux via BASH / Shell, we need to install ‘sysv-rc-conf’

aptitude install sysv-rc-conf

Below screenshot show the output of sysv-rc-conf command displaying status of service for all running levels (1-6) and startup (S)

2016-11-21 11_06_38-Debian1 [Running] - Oracle VM VirtualBox.png

As you can see in the screenshot to start a service use ‘+’ and to stop a service use ‘-‘. To enable or disable service to run at startup goto the respective service’s ‘S’ column and then use ‘Space Bar’.