ERROR MySQL: Can't connect to local MySQL server through socket

Currently I used OpenSUSE as my operating system, so to fix the issue as the title of this post is I'll modified the MySQL config at /etc/my.cnf. Open up the my.cnf config and go find the [client] section and uncomment these 2 lines below:

# port       = 3306
# socket     = /run/mysql/mysql.sock

Don't forget to change mode the my.cnf config file to 600, so just only you can edit it.

# chmod 600 my.cnf

To take effect, please restart mysql service.

# service mysql start

Now you can connect to mysql client by this command

# mysql -u root
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 8
Server version: 10.2.15-MariaDB openSUSE package

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

Let say you haven't set the root password yet, you could reset/set a new root password with this following step below.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)

MariaDB [(none)]> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

MariaDB [mysql]> show tables;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
-----------SNIP--------------
| user                      |
+---------------------------+
30 rows in set (0.00 sec)

Now set a new root password

MariaDB [mysql]> update user set password=PASSWORD("YOUR_NEW_PASSWORD") where User='root';

Query OK, 4 rows affected (0.00 sec)
Rows matched: 4  Changed: 4  Warnings: 0

And then tells MySQL to put the new changes.

MariaDB [mysql]> flush privileges;
Query OK, 0 rows affected (0.00 sec)

After all steps above done, you can now test it to connect to MySQL client with password that you've created.

# mysql -u root -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 9
Server version: 10.2.15-MariaDB openSUSE package

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

That's all.