How to run mysql on CentOS 7?

Question

MySQL

The Centos 7 system is installed. Initially, the MariaDB subd was installed, it had to be demolished. MySQL installed but I can't start the daemon.
Contents of the /etc/my.cnf file

# For advice on how to change settings please see
# dev.mysql.com/doc/refman/5.6/en/server-configurati...
[mysqld]
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0
# Recommended in standard MySQL setup sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
[mysqld_safe] log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

When trying sudo /sbin/service mysqld startor systemctl start mysqld
Outputs

Job for mysqld.service failed. See 'systemctl status mysql.service' and journalctl -xn' for details

$ systemctl status mysqld.service

mysqld.service - MySQL Community Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled)
   Active: activating (start-post) since Пн 2015-02-23 10:49:14 MSK; 16s ago
  Process: 11775 ExecStart=/usr/bin/mysqld_safe (code=exited, status=0/SUCCESS)
  Process: 11764 ExecStartPre=/usr/bin/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 11775 (code=exited, status=0/SUCCESS);         : 11776 (mysql-systemd-s)
   CGroup: /system.slice/mysqld.service
           └─control
             ├─11776 /bin/bash /usr/bin/mysql-systemd-start post
             └─12009 sleep 1

$ journalctl -xn

 "No journal files were found".

Answer 1

journalctl -xn
посмотрите его и лог Mysql
зачем было мариюбд удалять не понятно она таже самая мускуль и работает сразу из коробки

Answer 2

systemctl start mysqld