Enable the query cache in MySQL to improve performance

If you want to get optimized and speedy response from your MySQL server then you need to add following two configurations directive to your MySQL server:

query_cache_size=SIZE
The amount of memory (SIZE) allocated for caching query results. The default value is 0, which disables the query cache.

query_cache_type=OPTION
Set the query cache type. Possible options are as follows:
0 : Don’t cache results in or retrieve results from the query cache.
1 : Cache all query results except for those that begin with SELECT S_NO_CACHE.
2 : Cache results only for queries that begin with SELECT SQL_CACHE

Howto enable caching in MySQL

You can setup caching as follows:
$ 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 16Mb:

mysql> SET GLOBAL query_cache_size = 16777216;

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 = 268435456
query_cache_type=1
query_cache_limit=1048576

In above example the maximum size of individual query results that can be cached set to 1048576 using query_cache_limit system variable. Memory size in Kb.


Plesk12 what is the root password for MySQL?

Parallels Plesk Panel renames ‘root’ mysql account to ‘admin’ when the Panel is installed.
To get root privileges in mysql simply login with the ‘admin’ username instead. The password is the same as the admin password in Parallels Plesk Panel.

On server with Parallels Plesk Panel versions 8.x, 9.x and above admin password is stored in file /etc/psa/.psa.shadow. Use the following command to get the password:

~# cat /etc/psa/.psa.shadow

Since version 10 admin password stored in file /etc/psa/.psa.shadow is encrypted. Use the following command to get admin password in plain text:

~# /usr/local/psa/bin/admin –show-password

Despite version of Parallels Plesk Panel you may use the following command to login to mysql with root privileges:

~# mysql -uadmin -p`cat /etc/psa/.psa.shadow`


How-to enable gzip support on Nginx Plesk12

Create /etc/nginx/conf.d/gzip.conf with the following:

vim /etc/nginx/conf.d/gzip.conf
gzip on;
gzip_disable "MSIE [1-6]\.(?!.*SV1)";
gzip_proxied any;
gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript image/x-icon image/bmp image/svg+xml;
gzip_vary on;

restart ngix service from Plesk or ssh
gzip_types to compress other file types can be obtained from /etc/nginx/mime.types


Enabling error display in php via htaccess only

Note:- When using PHP as an Apache module, you can also change the configuration settings using directives in Apache configuration files (e.g. httpd.conf) and .htaccess files. You will need “AllowOverride Options” or “AllowOverride All” privileges to do so.

Add following values to your .htaccess

php_flag display_startup_errors on
php_flag display_errors on
php_flag html_errors on
php_flag log_errors on
php_value error_log /home/path/public_html/domain/PHP_errors.log


How to check the version of PHP ?

To verify the update is working create a simple testphp.php in your www directory with the following source code:

and open it in a web browser. The new PHP version should be reflected at the top of the page.

Or

ssh into the server or run the follwing command in terminal

php -v


How can I downgrade my version of PHP ?

Iphp 5.3 on Fedora 17 or Redhat using atomic repo.

You will need to remove php and httpd first (not compulsory)

yum remove php
yum remove httpd

Add the following at the end of /etc/yum.conf(if required)

exclude=php*5.4*

Install php from atomic repo

wget -q -O - http://www.atomicorp.com/installers/atomic | sh
yum install php

More details at 
http://www6.atomicorp.com/channels/atomic/fedora/17/x86_64/RPMS/