Mysql/en

Mysql is a handy database which is easy to manage using the phpmyadmin application. Using phpmyadmin requires HTTP server software as well for instance Apache2 or Nginx and Php5.

Installation

 aptitude install mysql-server

Give the mysql root user login password in installation. Do not forget the password. You can create more user accounts and change passwords later.

You can also use a mysql database without phpmyadmin but it helps a lot with managing it.

aptitude install mysql-client

• 

  Give password for MySQL server root user

• 

  Repeat root user password

MySQL configuration

Configuration file can be found in Ubuntu and Debian under:

 /etc/mysql/my.cnf

The port the MySQL server listens to. By default it is set to 3306.

[client]
port 3306

Address the server will listen to. Put a # number sign in front of the line and it will listen to all IP addresses.

bind-address               = 127.0.0.1

Command Line

Mysql databases can also be managed by command line.

You can connect to a mysql server with command line by:

 mysql -u root -p

Give the mysql root user password.

User Accounts

List user accounts:

  select host, user, password from mysql.user;

You can create a new user account with the command:

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

Give privileges for the new user account. The following command gives pretty much all privileges except the ones for modifying user accounts.

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

This command gives the user all privileges including databases and users accounts.

 GRANT ALL PRIVILEGES ON * . * TO 'newuser'@'%' WITH GRANT OPTION;

Confirm privileges:

 FLUSH PRIVILEGES;

Add certain privileges to a user account:

GRANT [type of permission] ON [database name].[table name] TO ‘[username]’@'localhost’;

Remove certain privileges from a user account:

 REVOKE [type of permission] ON [database name].[table name] FROM ‘[username]’@‘localhost’;

Remove user account:

  DROP USER ‘demo’@‘localhost’;

Master and Slave

Asynchronous synchronization of a MySQL server from Master server to Slave servers.

Master

This goes in the Master server's configuration:

 nano /etc/mysql/my.cnf

Add these to the end of mysqld

[mysqld]
...
log-bin=mysql-bin
server-id	= 1
auto_increment_increment = 10
auto_increment_offset = 1

Form connection to MySQL server:

mysql -u root -p

We create the user account replicant, with login rights from wherever % and password is just "password"

 create user replicant@'%' identified by 'password';

Define privileges for the user:

 GRANT SELECT, PROCESS, FILE, SUPER, REPLICATION CLIENT, REPLICATION SLAVE, RELOAD ON *.* TO replicant@'%';
 Flush Privileges; 

Slave

This goes in the Slave server's configuration:

Establish a connection to the database server and give the Master server's IP-address, username and password.

HANGE MASTER TO
MASTER_HOST='10.10.10.100',
MASTER_USER='replicant',
MASTER_PASSWORD='password';

Start the Slave server

Start slave;

Make sure that everything works:

show slave status\G

When synchronizing both ways, you must define the role for both servers, one Slave and one Master.

MYSQL and PHP5

You can fetch and send information to the MySQL database using PHP. This is simply done by the command:

 <?php
 mysqli_connect(host,username,password,dbname);
 mysqli_close($con);
 ?>

Modify this to for example:

 <?php
 //Establishing connection to database
 $con = mysqli_connect(127.0.0.1,root,Qwerty123,database);
 //Closing connection to database
 mysqli_close($con);
 ?>

So basically we select the server address, username, password and the database.

Printing from MySQL database:

 <?php
 $con=mysqli_connect("127.0.0.1","root","Qwerty123","database");
 if (mysqli_connect_errno()) {
 echo "Connecting failed. " . mysqli_connect_error();
 }
 $result = mysqli_query($con,"SELECT * FROM data");
 while($row = mysqli_fetch_array($result)) {
 echo $row['mysql'];
 }
 mysqli_close($con);
 ?>

Note that the database needs to have something written in it in order for you to print from it.

Save the previous configurations into mysql.php and then for instance write the following in the index.php file:

 <?php
 include_once ('mysql.php');
 ?>

You have to write this in every php file that will use the database.

Backup

Automysqlbackup

Sources

https://www.digitalocean.com/community/tutorials/how-to-create-a-new-user-and-grant-permissions-in-mysql