1. Create a new file /etc/yum.repos.d/city-fan.repo, then paste the following contents:

vi /etc/yum.repos.d/city-fan.repo

[CityFan]
name=City Fan Repo
baseurl=http://www.city-fan.org/ftp/contrib/yum-repo/rhel$releasever/$basearch/
enabled=1
gpgcheck=0

yum clean all
yum update curl

It's done, you could use curl -V to check the version of cURL.

This yum repo works for both RHEL and CentOS, all you have to do is specify the appropriate city-fan url.

In this post, I will explains how to use the command line to manage MySQL or MariaDB databases and users. I assuming that you already have MySQL server installed on your system and all the commands will be executed as root user.

To open the MySQL prompt, type the following command and enter the MySQL root user password when prompted:

# mysql -u root -p

Run the following command and replace db_name with the name of database you want to create:

mysql > CREATE DATABASE db_name;

If you try to create a database that already exists, you will see the following error message:

ERROR 1007 (HY000): Can't create database 'database_name'; database exists

To avoid creating duplicate database, we should use the following command:

mysql > CREATE DATABASE IF NOT EXISTS db_name;

Delete a MySQL database

Deleting a MySQL database is simple, but it is a non-reversible action, double check before executing the command. To delete a MySQL database, run the following command:

mysql > DROP DATABASE db_name;

If you try to delete a database that doesn't exists, you will see an error message, in order to avoid it, run the following command:

mysql > DROP DATABASE IF EXISTS db_name;

List all MySQL databases

You can list all the databases on your MySQL server with the following command:

mysql > SHOW DATABASES;

From the output, you may find that there are four databases not created by yourself. Don't worry, the information_schema, mysql, performance_schema, and sys databases are created by system and they are storing information about all other databases, system configuration, users, permission and other important data. These databases are necessary for the proper functionality of the MySQL installation.

Create a new MySQL user account

Run the following command, replace db_user with the user you want to create and user_password with the password you want to use:

mysql > CREATE USER 'db_user'@'localhost' IDENTIFIED BY 'user_password';

In the command above we have set the hostname part to localhost which means that this user will be able to connect to the MySQL server only from the localhost ( i.e from the system where MySQL Server runs). If you want to grant access from another host(s) just change the localhost with the remote machine IP or use '%' wildcard for the host part, which means that the user account will be able to connect from any host.

You also can add IF NOT EXISTS to the command to avoid creating duplicate user account:

mysql > CREATE USER IF NOT EXISTS 'db_user'@'localhost' IDENTIFIED BY 'user_password';

List all MySQL user account

It is pretty easy to list all MySQL user accounts by querying the mysql.users table:

mysql > SELECT user, host FROM mysql.user;

The output should looks similar to below:

+------------------+-----------+
| user             | host      |
+------------------+-----------+
| database_user    | %         |
| database_user    | localhost |
| debian-sys-maint | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+
6 rows in set (0.00 sec)

Delete MySQL user account

Run the following command to delete a user account, you can find the host part from the above command of listing all the user account:

mysql > DROP USER 'db_user@'localhost';

You also can add IF NOT EXISTS to the command:

mysql > DROP USER IF EXISTS 'db_user'@'localhost';

Display MySQL user account privileges

Run the following command to find the privileges granted to a specific user account:

mysql > SHOW GRANTS FOR 'db_user'@'localhost';

Change a MySQL user account password

According to different MySQL versions, there are different commands. You can find your MySQL server version by running the following command:

# mysql --version

If you have MySQL 5.7.6 and newer or MariaDB 10.1.20 and newer, to change the password use the following command:

mysql > ALTER USER 'db_user'@'localhost' IDENTIFIED BY 'new_password';

If you have MySQL 5.7.5 and older or MariaDB 10.1.20 and older, then use:

mysql > SET PASSWORD FOR 'db_user'@'localhost' = PASSWORD('new_password');

Grant permissions to a MySQL user account

To grand all privileges to a user account over a specific database, use the following command:

mysql > GRANT ALL PRIVILEGES ON db_name.* TO 'db_user'@'localhost';

To grand all privileges to a user account over all databases, use the following command:

mysql > GRANT ALL PRIVILEGES ON *.* TO 'db_user'@'localhost';

To grand all privileges to a user account over a specific table from a database, use the following command:

mysql > GRANT ALL PRIVILEGES ON db_name.table_name TO 'db_user'@'localhost';

To grant only specific privileges to a user account over a specific database, use the following command:

GRANT SELECT, INSERT, DELETE ON db_name.* TO db_user@'localhost';

Revoke permissions from a MySQL user account

If you need to revoke one or more privileges or all privileges from a user account, the command is almost identical to granting it. For example, if you want to revoke all privileges from a user account over a specific database, use the following command:

mysql > REVOKE ALL PRIVILEGES ON db_name.* TO 'db_user'@'localhost';

The passwd command changes passwords for user accounts for basic use. A normal user may only change the password for their own account, while the superuser may change the password for any account.

[root@server ~]# passwd [options] <username>

Running the passwd command without any argument will ask for a change of password for the user logged in.

[root@server ~]# passwd -S <username>

The -S option displays the status of user account password settings.

[root@server ~]# passwd -l <username>

The -l option is used to lock the password of a specified account, and it is available to root only. The result is that the user cannot use the password to log in to the system but can use other means such as SSH public key authentication.

[root@server ~]# passwd -u <username>

The -u option will unlock the password. This option works for an account that already has the password locked.

[root@server ~]# passwd -d <username>

The -d option is a quick way to delete a password for an account.

[root@server ~]# passwd -e <username>

The -e option is a quick way to expire a password for an account. The user will be forced to change the password during the next login attempt.

[root@server ~]# passwd -n <number of days> <username>

The -n option sets the number of days before a password can be changed. By default, a value of zero is set, which indicates that the user may change their password at any time.

To confirm the password setting made with the -n option above, run the following command:

[root@server ~]# passwd -S example_user
example_user PS 2020-12-04 10 99999 7 -1 (Password set, SHA512 crypt.)

The value of 10 after the date indicates the minimum number of days until the password can be changed.

[root@server ~]# passwd -x <number of MAX_DAYS> <username>

The -x option sets the maximum number of days a password remains valid. After MAX_DAYS, the password is required to be changed.

Confirm the setting with running the following command:

[root@server ~]# passwd -S example_user
example_user PS 2020-12-04 10 90 7 -1 (Password set, SHA512 crypt.)

The value of 90 after 10 indicates the maximum password lifetime.

[root@server ~]# passwd -w <number of days> <username>

The -w option will set the number of days in advance the user will begin receiving warnings that the password will expire.

[root@server ~]# passwd -i <number of INACTIVE days> <username>

The -i option is used to disable an account after the password has been expired for a number of days. After a user account has had an expired password for INACTIVE days, the user may no longer sign on to the account.

First, by running the following command to identify the version of MySQL or MariaDB, because we will use different commands to recover the root passwords:

$ mysql --version

After you've known your version of MySQL or MariaDB, following the steps to recover the root passowrd.

1. Stop the MySQL or MariaDB Service

$ systemctl stop mysql

2. Start the MySQL or MariaDB server without loading the grant tables

$ mysqld_safe --skip-grant-tables &

The ampersand & at the end of the command above will cause the program to run in the background , so you can continue to use the shell. When the --skip-grant-tables option is used, anyone can to connect to the MySQL or MariaDB server without a password and with all privileges granted.

$ mysql -u root

4. Set a new root password

Be careful, you need to run different commands to reset the root password according to the version, run the following commands if you run MySQL 5.7.6 and later or MariaDB 10.1.20 and later, replace NEW_PASSWORD with your own new password:

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'NEW_PASSWORD';
mysql> FLUSH PRIVILEGES;

Run the following commands if you have MySQL 5.7.5 and earlier or MariaDB 10.1.20 and earlier:

mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('NEW_PASSWORD');
mysql> FLUSH PRIVILEGES;

5. Stop and Start the database server normally

$ mysqladmin -u root -p shutdown

You will be prompted to enter the new root password, then start the service normally by running the following if you are using MySQL:

$ systemctl start mysql

Run the following commands if you are using MariaDB:

$ systemctl start mariadb

That's all and you have recovered the root password of MySQL or MariaDB successfully.