Linux Disk Usage

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I found a good link which lists good usages of the Linux command “du”.

This command allows me to see the usage in a ascending sort which is really helpful.

Tested on Linux.
du -h / | sort -h

Tested on Mac OS.
du -hs * | gsort -h

In case you don’t have gsort install coreutils.
brew install coreutils

This variation allows me to see any line which has the text “G” in it which basically allows me to see folders using space in GBs. Agreed it might give some folder names as well with “G” in it but I can bear with it.

Tested on Linux.
du -h /the/path | sort -h | grep "G"

Tested on Mac OS.
du -h /the/path | gsort -h | grep "G" 

Setting up Sonarqube docker instance

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In order to setup a fully functional Sonarqube server via docker I use the following consolidated command:


docker run \
--detach \
--name=sonarqube \
--publish 9000:9000 \
--publish 9092:9092 \
--env="SONARQUBE_JDBC_USERNAME=sonar" \
--env="SONARQUBE_JDBC_PASSWORD=sonar" \
--env="SONARQUBE_JDBC_URL=jdbc:mysql://mysql:3306/sonar?useUnicode=true&characterEncoding=utf8&rewriteBatchedStatements=true" \
--link mysql:mysql \
sonarqube:5.1

This connects my dockerized mysql instance with sonar and it is able to create tables and start using MySQL properly for storing all it’s data.

Setting up MySQL docker instance

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In order to setup a fully functional MySQL server via docker I use the following consolidated command:

docker run \
--detach \
--name=mysql \
--env="MYSQL_ROOT_PASSWORD=abcd1234" \
--publish 6603:3306 \
--volume=~/Docker/mysql/conf.d:/etc/mysql/conf.d \
--volume=~/Docker/mysql/mysql-datadir:/var/lib/mysql \
mysql

The advantage of the above approach is that the configuration files can be defined under ~/Docker/mysql/conf.d folder on my system and it will be picked up whenever I bootup this instance. The second thing is that all information written by this instance will be stored outside of VM in the path ~/Docker/mysql/mysql-datadir on my system. So In case this VM goes away due to some unexplained reasons I can still bootup another docker instance of MySQL and point it to this data directory.

Maven: Installing / adding local jar into your local maven repository

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I needed to install a local jar file into my laptop’s local maven repository and found this article. I used this approach to install this jar file in my repo:

mvn install:install-file -Dfile=my-model-1.2.1.jar -DgroupId=com.cyberaka.my.package -DartifactId=my-model -Dversion=1.2.1 -Dpackaging=jar -DgeneratePom=true

This duly added the local jar file under appropriate group id and artifact id inside my maven repository and I was able to refer to this dependency through my project’s pom.

 

Using NGINX for Proxy Pass

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Lets say I have two servers running on my laptop
1. http://localhost:3000 – This is the UI
2. http://localhost:4000 – This is the web services API

So now I need to setup something like this:
1. http://localhost/ – This should point to UI
2. http://localhost/api/ – This should point to web services API

To set this up I have used NGINX and added this section in the “server” section of the nginx.conf file. On my Mac system this file is located at: /usr/local/etc/nginx/nginx.conf

location /api/ {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://localhost:4000/;
}

location / {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://localhost:3000/;
}

To reload NGINX I use the “-s reload” parameter for nginx. On my Mac I execute this command:
/usr/local/Cellar/nginx/1.10.0/bin/nginx -s reload

User input in shell script

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I needed to write a small shell script which would allow me to make some decision based on user choices. I needed the user to specify Yes, No or Cancel for an operation. The following piece of hack does the job well.

#! /bin/bash

# define constants
declare -r TRUE=0
declare -r FALSE=1

user_choice() {
local str="$@"
while true
do
# Prompt user, and read command line argument
read -p "$str " answer

# Handle the input we were given
case $answer in
[yY]* ) return $TRUE;;

[nN]* ) return $FALSE;;

[cC]* ) exit;;

* ) echo "Y - Yes, N - No, C - Cancel. Please choose valid option.";;
esac
done
}

if user_choice "Execute Job 1? "; then
echo "Executing Job 1.."
fi
if user_choice "Execute Job 2? "; then
echo "Executing Job 2.."
fi

The following links were referred to achieve this little script:
http://linuxcommand.org/wss0090.php
https://bash.cyberciti.biz/guide/Returning_from_a_function
http://alvinalexander.com/linux-unix/shell-script-how-prompt-read-user-input-bash