January 2017 – ManthanHD

Generating random passwords from linux command line

23rd January 2017 / Leave a Comment

Managing production passwords isn’t a trivial task. I was trying to deploy a containerized app the other day that had a database deployed with it. During the deployment, I was trying to find an easy way to set a secure password. I didn’t want anyone to know the password because I wanted only the application to know it and no one else. Also, the container was setup in a way that the database cannot be accessed from the outside world.

So instead of hard-coding the password, after doing some research, I used the following command:

Setting up corporate proxy on Docker for mac

19th January 2017 / Leave a Comment

Working with Docker on corporate proxy is a painful experience. Mainly because there aren’t many guides available to do it. Finally after banging my head on the desk for a long time, my friend and colleague at https://nextmetaphor.io showed me how to do it.

First of all, fire up your terminal and open up docker tty in screen.

screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty

1	screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty

If you see a blank screen, press enter. You should see a prompt.

Make sure you are in the docker VM by typing the hostname command. You should see the response as moby. If your response is other than that, try that screen command again.

/ # hostname
moby

1 2	/ # hostname moby

Now we want to view docker’s routing table. This is because we’ll need to find out the IP address of the host machine that is running the proxy. This is specific to my setup where I have a charles proxy server running on my machine which proxies to the remote corporate proxy.

/ # netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.65.1    0.0.0.0         UG        0 0          0 eth0
172.17.0.0      0.0.0.0         255.255.0.0     U         0 0          0 docker0
192.168.65.0    0.0.0.0         255.255.255.240 U         0 0          0 eth0

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/ # netstat -rn

Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

0.0.0.0 192.168.65.1 0.0.0.0 UG 0 0 0 eth0

172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0

192.168.65.0 0.0.0.0 255.255.255.240 U 0 0 0 eth0

Get the gateway entry for 0.0.0.0. In my case this is 192.168.65.1. That’s the IP for the host machine running docker. For the proxy running on your local machine, just map it to the port. My charles server is running on port 8099 so my proxy will be:

http://192.168.65.1:8099

Close screen by pressing Ctrl + a \ key. Once you’ve exited, open up docker for mac preferences.

Go to the “advanced” tab and fill out your proxy settings.

Hit apply and restart when done!

Your Docker for Mac should now work harmoniously with your proxy!

CodeEval: Fizz Buzz (Java)

2nd January 2017 / Leave a Comment

Finally managed to get some spare time in order to do this. Helped be clear my head a bit. Here’s my quick 1 minute solution to CodeEval’s fizz buzz problem in Java:

/* Sample code to read in test cases:*/
import java.io.*;
public class Main {
    public static void main (String[] args) throws IOException {
        File file = new File(args[0]);
        BufferedReader buffer = new BufferedReader(new FileReader(file));
        String line;
        while ((line = buffer.readLine()) != null) {
            line = line.trim();
            final String[] inputStringArray = line.split(" ");
            final int divisor1 = Integer.parseInt(inputStringArray[0]);
            final int divisor2 = Integer.parseInt(inputStringArray[1]);
            final int countingLength = Integer.parseInt(inputStringArray[2]);
            
            for(int i = 1; i <= countingLength; i++) {
                final StringBuilder responseBuilder = new StringBuilder();
                if(i % divisor1 == 0) responseBuilder.append("F");
                if(i % divisor2 == 0) responseBuilder.append("B");
                if(responseBuilder.length() == 0) responseBuilder.append(i);
                System.out.print(responseBuilder.toString() + " ");
            }
            
            System.out.println();
        }
    }
}

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/* Sample code to read in test cases:*/

import java.io.*;

public class Main {

public static void main (String[] args) throws IOException {

File file = new File(args[0]);

BufferedReader buffer = new BufferedReader(new FileReader(file));

String line;

while ((line = buffer.readLine()) != null) {

line = line.trim();

final String[] inputStringArray = line.split(" ");

final int divisor1 = Integer.parseInt(inputStringArray[0]);

final int divisor2 = Integer.parseInt(inputStringArray[1]);

final int countingLength = Integer.parseInt(inputStringArray[2]);

for(int i = 1; i <= countingLength; i++) {

final StringBuilder responseBuilder = new StringBuilder();

if(i % divisor1 == 0) responseBuilder.append("F");

if(i % divisor2 == 0) responseBuilder.append("B");

if(responseBuilder.length() == 0) responseBuilder.append(i);

System.out.print(responseBuilder.toString() + " ");

}

System.out.println();

}

ManthanHD

Findings, thoughts and observations from the eye of a Software Engineer.

Month: January 2017

Generating random passwords from linux command line

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Setting up corporate proxy on Docker for mac

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CodeEval: Fizz Buzz (Java)

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