Top 10 Linux commands - Basic Linux commands

If you are new to Linux, you should start getting familiar with Linux commands. Let us take a look at top 10 commands.

1. ls

ls command will list all the files in the directory.

2. cp

cp command will copy the files from source to dest folder

3. mv

mv command will copy the files from source to dest folder

4. rm

rm command will remove file from file system.

5. cd

cd command changes the directory

6. mkdir

mkdir creates new directory.

7. cat

cat command displays the content of a file

8. sudo 

Every single command that needs root's permission, need this sudo command. You can use sudo before each command that requires root permissions -

 

9. grep

 

You need to find a file but you don't remember its exact location or the path. grep will help you to solve this problem. You can use the grep command to help finding the file based on given keywords. 

10. poweroff

poweroff command is used to poweroff directly from terminal.

Ansible playbook for installing Apache on Redhat Linux

---
 - hosts: Apache_Group
   become: true
   tasks:
     - name: install the latest version of Apache
       yum:
         name: httpd
         state: latest

     - name: ensure apache started
       service: name=httpd state=started enabled=yes

How to install Sonarqube on Redhat enterprise Linux - Install Sonarqube on Redhat enterprise Linux (RHEL)

SonarQube is popular static code analysis tool. It is Java based tool. Here are the steps for installing Sonarqube.

first you need to install a database as SonarQube uses database to store code quality report. We can use MySQL, Postgres, Oracle or MSSQL. Here are the steps for setting up SonarQube using MySQL database :

sudo yum update -y

sudo yum install wget -y

MySQL installation steps:

sudo wget http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm  

sudo rpm -ivh mysql-community-release-el7-5.noarch.rpm

sudo yum install mysql-server -y

Start MySQL service

sudo systemctl start mysqld

sudo mysql_secure_installation

enter n as we will not be setting any admin password for user root.

Would you like to setup VALIDATE PASSWORD component?
type n

now set up password for root user

Remove anonymous users?
type y
for Disallow root login remotely?
type y
for Remove test database and access to it?
type y
for Reload privileges tables
type y

Setup Sonarqube user and password

mysql -u root -p

SHOW GLOBAL VARIABLES LIKE 'storage_engine';

CREATE USER 'sonar'@'localhost' IDENTIFIED BY 'password';

CREATE DATABASE sonar;

GRANT ALL PRIVILEGES ON sonar.* TO 'sonar'@'localhost';

now type exit to come out of MySQL.

Sonarqube web server installation steps:

Start with java installation.

sudo wget --no-check-certificate --no-cookies --header 'Cookie: oraclelicense=accept-securebackup-cookie' 'http://download.oracle.com/otn-pub/java/jdk/8u141-b15/336fa29ff2bb4ef291e347e091f7f4a7/jdk-8u141-linux-x64.rpm'

sudo rpm -i jdk-8u141-linux-x64.rpm

now type java -version to make sure Java 8 is installed.

Download SonarQube

cd /opt 

sudo wget https://binaries.sonarsource.com/Distribution/sonarqube/sonarqube-6.7.6.zip

sudo yum install unzip -y

sudo unzip sonarqube-6.7.6.zip

sudo mv sonarqube-6.7.6 sonarqube

Modify Sonar Conf file

sudo vi /opt/sonarqube/conf/sonar.properties

uncomment the below lines by removing #:

sonar.jdbc.username=sonar

sonar.jdbc.password=password

sonar.jdbc.url=jdbc:mysql://localhost:3306/sonar?useUnicode=true&characterEncoding=utf8&rewriteBatchedStatements=true&useConfigs=maxPerformance

sonar.web.host=0.0.0.0

sonar.web.javaOpts=-Xmx512m -Xms256m -XX:+HeapDumpOnOutOfMemoryError

sonar.ce.javaOpts=-Xmx512m -Xms256m -XX:+HeapDumpOnOutOfMemoryError

Run Sonarqube as sonar user
create a user called sonar by executing below command:
sudo useradd sonar

sudo chown -R sonar:sonar /opt/sonarqube

Edit the sonar.sh start script and change the #RUN_AS_USER to be RUN_AS_USER=sonar

sudo vi /opt/sonarqube/bin/linux-x86-64/sonar.sh

Change 
RUN_AS_USER=sonar

now start the server 

sudo sh /opt/sonarqube/bin/linux-x86-64/sonar.sh start

for any issues, look at logs at 

tail -f /opt/sonarqube/logs/sonar.log

Verify by going to browser http://hostname:9000