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Operating System

How to Fix Pg_ctl command not found

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Sometimes after a fresh PostgreSQL install if we want to start or stop from PostgreSQL rather than controlling the PostgreSQL instance start and stop from the root. And when we run the pg_ctl from the command prompt as a PostgreSQL Linux user we see the error bash: pg_ctl: command not found… 

In this article, lets learn how to fix it

As PostgreSQL check your pg base directory 

 

And now add this PostgreSQL to the Linux path so that it’s always available. I would recommand to create a postgresql env. file so that it more easy to handle rather than messing with other systems runing on linux operating system.

				
					--Step 1 
-bash-4.2$ echo $PGDATA
/var/lib/pgsql/10/data

--Step 2
-bash-4.2$ echo "PATH=/usr/pgsql-10/bin:$PATH">>~/.postgre_10.profile

--Step 3
chmod 777 .postgre_10.profile

--Step 4 
. .postgre_10.profile

--Step 5
Check pg_ctl now

-bash-4.2$ pg_ctl --version
pg_ctl (PostgreSQL) 10.17
-bash-4.2$

HA Proxy For MySQL Master – Slave

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There are scenarios where we have to provide the high ability to MySQL database instances and we use the Master and Slave replication method of MySQL database.

In the same case to segregate the Read and Write database traffic. We widly use HA- Proxy. It is a feature rich open source Load blancing tool with many unique features like reverse proxy but in out case we are going to use it only for Hight aviliblity purpose.

				
					root@haproxy01:~# haproxy -v
HA-Proxy version 2.0.13-2ubuntu0.3 2021/08/27 - https://haproxy.org/

 

How to Install it?

You simply use yum or apt commands to install it

				
					sudo apt install -y haproxy

 

Check  the version 

 

 

 

 

Install Mysql Client for HA Proxy Node to communicate with mysql master and slave databases.

 

				
					apt-get install -y mysql-client
cd /etc/haproxy/
cp haproxy.cfg haproxy.cfg_org
vim haproxy.cfg

				
			
				
					root@haproxy01:~# cat /etc/haproxy/haproxy.cfg
global
	log 127.0.0.1 local0 notice
        log /dev/log    local0
  	user haproxy
	group haproxy

	# Default SSL material locations

defaults
	log global
	mode tcp
        option tcplog
	retries 2
	timeout client 30m
	timeout connect 4s
    	timeout server 30m
	timeout check 5s

listen stats
        mode http
        bind *:9201
        stats enable
        stats uri /stats
        stats realm Strictly\ Private
        stats auth admin:admin

listen mysql-cluster
       bind *:3306
       mode tcp
       option mysql-check user haproxy_user
       balance roundrobin
       server master 192.168.56.205:3306 check
       server slave1 192.168.56.206:3306 check

listen mysql-cluster1
    bind 192.168.1.208:3306
    mode tcp
    option mysql-check user haproxy_user
    balance roundrobin
    server mysql-1 192.168.1.205:3306 check
    server mysql-2 192.168.1.206:3306 check

Create HA proxy user on mysql01/205 on primary node

				
					GRANT ALL PRIVILEGES ON *.* TO 'haproxy_root'@'%' IDENTIFIED BY 'Oracle@123' WITH GRANT OPTION;

flush privileges;

Test the configuration and it should start without error & Target should come up on GUI

				
					haproxy -f /etc/haproxy/haproxy.cfg -db

systemctl restart haproxy.service

Check HA proxy GUI and see all the MySQL target is up and running fine using HA Proxy Admin link:

HA Proxy Link Structure:

http://<localhost or IP/HostName/stats

http://192.168.1.208:9201/stats

Default Credentials : 

UserName : admin

Password: admin

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Essential AWS Services for Database Administrators to Learn

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Why AWS?

Cloud is becoming a vital part of Database Administration because it provides various database services & Infrastructure to run Database Ecosystems instantly. AWS (Amazon Web Services) is one of the pioneers in the Cloud according to the Gartner magic quadrant. Knowing more cloud infrastructure technologies is going to give more mileage to your Administrator career. In this article, you will find some of the AWS services which Database Administrators should know as they are basic to run Database opration.

Essential AWS Services List For Database Administrator (DBA)

Network
VPCs
Subnets
Elastic IPs
Internet Gateways
Network ACLs
Route Tables
Security Groups
Private Subnets
Public Subnets
AWS Direct Connect

Virtual Machine 
EC2
AWS Work Space

Storage
EBS
EFS
S3

Database as Services (RDS)
MySQL / MariaDB
PostgreSQL
Oracle
Micrsoft SQL Server
AWS Aurora PostgreSQL/MySQL

Database Managed Services
AWS Dynamo DB
AWS Elasticsearch 
Amazon DocumentDB

Messaging & Event Base Processing 
Apache Kafka (Amazon MSK)

 

Warehousing/ OLAP /Analytics Stagging DB
AWS Redshift

 

Monitoring 
Cloud watch
Amazon Grafana
Amazon Prometheus

 

Email Service
Amazon Simple Notification Service

Security 
IAM
Secrets Manager

Database Task Automation
AWS Batch
AWS Lambda
Cloud Formation

Command-line interface (CLI) to Manage AWS Services
AWSCLI

Migration 
Database Migration Service

Budget 
AWS Cost Explorer
AWS Budgets

Some other Services & Combination worth of Exploring

Bastion Host For DBA
MongoDB running on EC2
ELK (Elastic Search , LogStach, Kibana) running on EC2
Tunnels for Non stranded ports for Database Connections for more security
pg_pool or pg_Bouncer for PostgreSQL Databases

Stay Tuned For Latest Database, Cloud & Technology Trends

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How to Fix Cannot open your terminal ‘/dev/pts/2’ – please check

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Normally we see a common error when we switch or sudo to a user to run the screen session and it gets closes with the error ‘Cannot open your terminal ‘/dev/pts/2′ – please check’. fix it very tiny but it took a long for me to find so I thought I will share the quick fix and save our prices time.

Error:

[thedbadmin@testdb01 ~]$ screen -x 12991.screen_testCannot open your terminal ‘/dev/pts/0’ – please check.[thedbadmin@testdb01 ~]$

Step 1: logout from the user that you have logged in.

Step 2: log as your user or from where you want to run screen and just give full privileged to /dev/pts/* 

Fix : 
$ chmod 777 /dev/pts/*

 

Note: if you get any warning or error after executing the above command,  just ignore it safely.

Now you can start the screen again hopefully you won’t see that error again

Happy programming !!!

How to fix Rocky Linux full screen issue on Oracle Virtual Box

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In this article, we will fix the rocky Linux full-screen issue on the oracle virtual box. Normally after installing rocky Linux on virtual box by default full scree don’t work and some times its annoying because it little hard to work with small screen. Let me give you few simple steps with commands which will fix this issue and you will many option to set screen resolution on rocky Linux.

 

Step 1: login as root and run following commands.

Commands:

yum install dkms gcc make kernel-devel bzip2 binutils patch libgomp glibc-headers glibc-devel kernel-headers -y

Important Note: In case if you don’t find the yum packages, configure epel yum repository for centos 8

 

Step 2: Install the virtual box guest addition. You can see the navigation from flowing screenshot

Step 3: restart your rocky Linux virtual machine

Command:

[root@rocky01 ~]# reboot

You are Done !!!

 

 

Read More

Take MySQL backup From Jenkins Job

How to fix ORA-28368: cannot auto-create wallet
AWS Services and their Azure alternatives 
How to Manage AWS S3 Bucket with AWS CLI

How to connect PostgreSQL Database from PgAdmin
How to create AWS rds PostgreSQL Database
Convert pem to ppk
How to Install PuTTy on Window
How to Install and create AWS EC2 Instance using Terraform
AWS MySQL RDS Database Creation using AWSCLI
How to Create MySQL Database with AWS RDS
How to connect to AWS MySQL / MariaDB RDS or EC2 database from MySQL WorkBench

Take MySQL backup From Jenkins Job

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Take MySQL Database Backup From Jenkins

In this post, we will explain and practically show how you can configure MySQL database backup using Jenkins jobs. in easy words, you will automate the MySQL database backup process from Jenkins GUI and MySQL dump command. Normally we use MySQL dump from CLI or using the windows option. In this case, just automate the MySQL dump triggering from a shell script which will be called by Jenkins job with parameter. MySQL dump needs few parameters to run just pass them by build with parameter option in jenkins.

 

1. Log to Jenkins default URL and port: http://192.168.56.21:8080/

If you want to install and setup Jenkins see this article

2. Go to New items

3.  Give some Name and select FreeStyle project

 

4.  In the build section click on Add build step radio button and select Execute shell.

5. Select boolean parameter for MySQL database host and database superuser password which is root password in MySQL database case.

 

6.  In this build part give the shell script name with full path and parameters like $HOST_IP & $Password

 

Shell Script

[root@master01 ~]# cat /opt/jenkins_scripts/mysql_full_db_backup.sh
#!/bin/bash
HOST_IP=$1
PASSWORD=$2
echo "starting mysql database full backup"
mysqldump -h $HOST_IP --all-databases --single-transaction --quick --lock-tables=false > /opt/jenkins_scripts/mysql_backup/full_backup_$(date +%F_%N).sql -u root -p$PASSWORD
echo "Backup has been done"

 

[su_box title=”IMP Note” box_color=”#fe2227″ title_color=”#101112″]Note: Make sure Jenkins have execute (chmod +x /opt/jenkins_scripts/mysql_full_db_backup.sh)  privilege on script[/su_box]

 

7. Let’s execute the Jenkins job

7.1  click on the the MySQL database backup job

 

7.2  Click on build with Parameter

 

7.3  Give your database server name or IP. In my case Mysql database running on the same server that’s thy, I will give localhost and database root password

 

7.4 Once your job is executed go to that job open it in console output mode and check the status of the job. And you are DONE!!!

Read More

How to fix ORA-28368: cannot auto-create wallet
AWS Services and their Azure alternatives 
How to Manage AWS S3 Bucket with AWS CLI

How to connect PostgreSQL Database from PgAdmin
How to create AWS rds PostgreSQL Database
Convert pem to ppk
How to Install PuTTy on Window
How to Install and create AWS EC2 Instance using Terraform
AWS MySQL RDS Database Creation using AWSCLI
How to Create MySQL Database with AWS RDS
How to connect to AWS MySQL / MariaDB RDS or EC2 database from MySQL WorkBench