Hacks on My Notes

Windows cmd & hotkey - 1

Wed, 09 Mar 2011 10:59:31 +1100

Do you want to make your friends amazed by your computer skill and praise you as genius? Or the hacker as watched in Sci-Fi movies? You don’t need Mac, Linux or other operating systems, just Windows, you can show-off and look like hacker and master of Zeroes and Ones, even you have no any idea of it. Here are some tricks by which you can make your friends’ jaw drop.

Windows cmd & hotkey - 2

Sat, 24 Mar 2012 10:59:31 +1100

This article will continue the topic of Windows command & hotkeys. Part-1 shows you common hotkeys and short command lines for Run windnow dialog. The rest of this topic will focus on the advanced commands and how to create a batch script with all those commands.

Let me clarify something first. Advanced command here does not mean that commands here are very complicated or much more powerful than common ones, which have been shown in the Part-1. Here we call them advanced, because they are used by experienced users to complete their given tasks, and those commands are used seldom by majority people. Comparing with Part-1, advanced commands have some specific features which allow them to do some special jobs, which usually are done by system admin. Advanced command is known as Admin command as well.

Windows cmd & hotkey - 3

Sun, 04 May 2014 10:59:31 +1100

This article will continue the topic of Windows command & hotkeys. Part-1 shows you common hotkeys and short command lines for Run window dialog. Part-2 advanced commands and how to create a batch script with all those commands. Here I am going to show you another secret weapon in Windows system-VBScript/JScript

Breif history#

VBScript/JScript is an Active Scripting language developed by Microsoft that is modeled on Visual Basic. It allows Microsoft Windows system administrators to generate powerful tools for managing computers with error handling, subroutines, and other advanced programming constructs.

SFTP & GPG

Tue, 04 Dec 2018 14:59:31 +1100

SFTP#

SFTP (SSH File Transfer Protocol) is a secure file transfer protocol. It runs over the SSH protocol. It supports the full security and authentication functionality of SSH.

SFTP has pretty much replaced legacy FTP as a file transfer protocol, and is quickly replacing FTP/S. It provides all the functionality offered by these protocols, but more securely and more reliably, with easier configuration. There is basically no reason to use the legacy protocols any more.

Git Practices

Thu, 11 Aug 2016 11:59:31 +1100

Push existing repository to remote#

Update the remote git url

 $ git remote set-url origin [your_new_repo_url]

Push it remote branch master/main
```
 $ git push -uf origin [master/main]
```

Create a new branch with git#

Create the branch locally#

Create the branch on your local machine and switch in this branch
```
 $ git checkout -b [name_of_your_new_branch]
```

Push the branch#

Push the branch on git-repository (Github, Bitbucket)

Cassandra Practices

Mon, 01 Jan 0001 00:00:00 +0000

Apache Cassandra is a free open-source database system that is NoSQL based. Meaning Cassandra does not use the table model seen in MySQL, MSSQL or PostgreSQL, but instead uses a cluster model. It’s designed to handle large amounts of data and is highly scalable.

Install Cassandra on Ubuntu#

Install Java(JRE) 8+#

sudo add-apt-repository ppa:webupd8team/java
sudo apt update
sudo apt-get install oracle-java8-set-default
java -version

Install Python 2.7+#

sudo apt install python
python --version

Install Cassandra#

First, we have to add Cassandra repository to source list by running following command. The 39x is the version. Use 40x if Cassandra 4.0 is the newest version:

echo "deb http://www.apache.org/dist/cassandra/debian 39x main" | \
sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list

Next, run the cURL command to add the repository keys :

curl https://www.apache.org/dist/cassandra/KEYS | \
sudo apt-key add -

We can now update the repositories and install Cassandra:

sudo apt-get update
sudo apt install cassandra
# optional - It works on MacBook
sudo reboot

Check Cassandra status

nodetool status

Install Cassandra with Docker#

Create node n1#

docker run --name n1 -d tobert/cassandra -dc DC1 -rack RAC1
docker ps

Get IP of node n1#

IP=`docker inspect -f '{{ .NetworkSettings.IPAddress }}' n1`
echo $IP

Check status of n1#

docker exec -it n1 nodetool status

# You will see status of Datacenter D1 below

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# -- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.2 51.53 KB 256 100.0% 8965869d-cae8-41a6-bf19-ff69c2605c6c RAC1

Create node n2 on rack RAC2#

docker run --name=n2 -d tobert/cassandra -dc DC1 -rack RAC2 --seeds $IP

docker exec -it n1 nodetool status

# You will see status of Datacenter D1 below

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# -- Address Load Tokens Owns (effective) Host ID Rack
# UN 172.17.0.3 72.01 KB 256 100.0% cfa002b0-350c-41b8-9f86-eb8978a43b26 RAC2
# UN 172.17.0.2 51.53 KB 256 100.0% 8965869d-cae8-41a6-bf19-ff69c2605c6c RAC1

Check node n2 configuration#

docker exec -it n2 cat /data/conf/cassandra.yaml | grep endpoint
docker exec -it n2 cat /data/conf/cassandra-rackdc.properties | grep -e "dc" -e "rack"

Create node n3 on Datacenter D2 and rack RAC1#

docker run --name=n3 -d tobert/cassandra -dc DC2 -rack RAC1 --seeds $IP
docker exec -it n1 nodetool status

# You will see status below. It may take a few seconds to get everything up and run.

# Datacenter: DC1
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# -- Address Load Tokens Owns (effective) Host ID Rack
# UN 172.17.0.3 134.03 KB 256 66.1% cfa002b0-350c-41b8-9f86-eb8978a43b26 RAC2
# UN 172.17.0.2 102.84 KB 256 64.5% 8965869d-cae8-41a6-bf19-ff69c2605c6c RAC1

# Datacenter: DC2
# ===============
# Status=Up/Down
# |/ State=Normal/Leaving/Joining/Moving
# -- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.4 14.38 KB 256 69.4% 0fad8335-763d-42fa-9934-3ed10c44eaa8 RAC1

Setup replication strategy#

docker 
create keyspace csdb with replication = {'class':'NetworkTopologyStrategy','DC1':2,'DC2':1}

Check csdb status#

docker exec -it n1 nodetool describering csdb

# Run nodetool status and note that the one node in DC2 owns all the data
docker exec -it n1 nodetool status csdb 

# Stop and remove all four docker containers:
docker stop n1 n2 n3 n4; docker rm n1 n2 n3 n4

Create single Datacenter with 3 nodes#

Create 3 nodes with local mounted directory#

docker run --name=n1 -v $PWD/ws/ps/cassdev/scripts:/scripts -d tobert/cassandra
docker exec -it n1 nodetool status

IP=`docker inspect -f '{{ .NetworkSettings.IPAddress }}' n1`
echo $IP

docker run --name=n2 -d tobert/cassandra --seeds $IP
docker run --name=n3 -d tobert/cassandra --seeds $IP

docker exec -it n1 /bin/bash
cd scripts

List scripts#

docker exec -it n1 /bin/bash
cd /scrpts && ls

Create keyspace with simple replication#

docker exec -it n1 cqlsh
create keyspace csdb with replication = 
{'class':'SimpleStrategy', 'replication_factor':1};

Create table and insert data with script#

docker exec -it n1 cqlsh

> desc keyspaces;
> desc tables;
> use ussdb;
> source '/scripts/courses.cql'
> source '/scripts/users.cql'

CQL#

docker exec -it n1 cqlsh

> use ussdb;
> desc tables;
> select * from users;
> select * from courses;

Troubleshoot#

Connection error

Debug PHP with Free IDE

Mon, 01 Jan 0001 00:00:00 +0000

PDT and Netbeans#

PDT and Netbeans are two most popluar free PHP IDEs. We choose such IDE for productivity, so code intelligence and debug are two key factors, which let us love IDE. Because both are not created for PHP development at the start, there is no built-in server to support the PHP web debug. When we want to use it to debug, we would come across some wierd problems. Here is how to prepare the IDE for PHP debug.

Docker Practices

Mon, 01 Jan 0001 00:00:00 +0000

Docker is an open platform for developing, shipping, and running applications. Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security allow you to run many containers simultaneously on a given host. Containers are lightweight because they don’t need the extra load of a hypervisor, but run directly within the host machine’s kernel. This means you can run more containers on a given hardware combination than if you were using virtual machines. You can even run Docker containers within host machines that are actually virtual machines!

Qemu & Virtual Machine

Mon, 01 Jan 0001 00:00:00 +0000

What is Qemu ?

QEMU is free and open source. And is licensed under GPL 2. it has the ability to run under both KVM and XEN models (if you enabled virtualization technology from your BIOS first) and offers a lot of options and virtualization options. In this article, we’ll explain how to use QEMU and install it.

QEMU is a virtualization technology emulator that allows you to run operating systems and Linux distributions easily on your current system without the need to install them or burn their ISO files. It is like VMware or VirtualBox. You can use it at anytime to emulate running any operating system you want on a lot of devices and architecture.

VirtualBox Notes

Mon, 01 Jan 0001 00:00:00 +0000

Network#

Not attached.#

In this mode, Oracle VM VirtualBox reports to the guest that a network card is present, but that there is no connection. This is as if no Ethernet cable was plugged into the card. Using this mode, it is possible to “pull” the virtual Ethernet cable and disrupt the connection, which can be useful to inform a guest operating system that no network connection is available and enforce a reconfiguration.