How to use mysqldump

What's mysqldump?
It dumps Mysql or MariaDB contents. Basically it is used for backup.

Basic Usage

# Extract database definition
mysqldump -h <host> -u <user> -p <password> -d <database name>

# Extract table definition
mysqldump -h <host> -u <user> -p <password> -t <database name> <table name>

# Specify where condition when extracting table
mysqldump -h <host> -u <user> -p <password> -t <database name> <table name> --where="condition"

How to clear cache on CentOS

clear page cache
sudo echo 1 > /proc/sys/vm/drop_caches
or
sudo sysctl -w vm.drop_caches=1

clear directory entry and inode
sudo echo 2 > /proc/sys/vm/drop_caches
or
sudo sysctl -w vm.drop_caches=2

clear page cache and directory entry and inode
sudo echo 3 > /proc/sys/vm/drop_caches
or
sudo sysctl -w vm.drop_caches=3