No matter stop, start or mysql connection, there are different error messages. The specific error messages are:

# service mysqld stop
ERROR! MySQL server PID file could not be found!

# service mysqld start
Starting MySQL.. ERROR! The server quit without updating PID file (/data/mysql/mysql.pid).

# mysql -uroot -p
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2)

1. Error reason:

In fact, the above three different MySQL errors are all caused by one reason: the root directory disk is full.

2. Check the large files that cause the disk to be full:

1. First, use the df command to check the disk usage:
# df
You may see in the output:
/dev/mapper/VolGroup-lv_root 39841176 37788792 28552 100% /

2. Use # du – sh * to view large files. For example, the root directory is data. Use the command to view:
# cd/data
# du – sh *
You will find that the mysql folder occupies more than n gigabytes, and then view which files:
# cd mysql
# du – sh *
You will find many large files, such as
581M mysql-bin.000029
28K mysql-bin.000030
7.6G mysql-bin.000031
4.0K mysql-bin.000032

These files are MySQL Binary Log binary files, which are mainly used for data recovery and master-slave replication of master-slave servers.

Since I have no master and slave servers, I decided to delete them.

3. Solution:

1. Delete these large files:
# rm -rf mysql-bin.000031
~~~

2. After deleting them, open my.cnf under /etc/, find
log-bin=mysql-bin
binlog_format=mixed
Comment out these two lines, that is, add the “#” sign in front:
#log-bin=mysql-bin
#binlog_format=mixed

3. Restart the MySQL server, and it is OK
service mysqld restart