Log into your mysql

$ mysql -u root –p

Output:

Enter password:

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 16 to server version: 4.1.15-Debian_1-log
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.

mysql>

Now setup cache size 32Mb:
mysql> SET GLOBAL query_cache_size = 33554432;    

Query OK, 0 rows affected (0.00 sec)

mysql> SHOW VARIABLES LIKE 'query_cache_size';

Output:

+——————+———-+

| Variable_name | Value |

+——————+———-+

| query_cache_size | 16777216 |

+——————+———-+

You can setup them in /etc/my.cnf (Red Hat) or /etc/mysql/my.cnf (Debian) file:
# vi /etc/my.cnf
Append config directives as follows:

query_cache_size = 33554432
query_cache_type=1
query_cache_limit=2096576