Archive for April, 2010

Finding MySQL server operating parameters

If you have a MySQL server listening on a given port number, you can use the following command to find out what operating parameters it is using for several important configurable variables, including the base directory and Unix socket file name:

# mysqladmin –host=host_name –port=port_number variables

With the information displayed by that command, you can tell what option values not to use when configuring an additional server.

Got a packet bigger than ‘max_allowed_packet’ bytes

If you get this error when trying to dump a MySQL DB, this is due to the packet limit of MySQL server.

To solve this issue, add an extra entry into /etc/my.cnf file under [mysqld] group:

max_allowed_packet = 100M

This will reset the limitation to 100Mb for file insertion into blob type (or longblob) column. Then restart mysql server:

/sbin/service mysql restart


Catch-all/default address behavior for new accounts in Cpanel.

The catch-all or default address handles email sent to nonexistent users on your server’s domains. It is useful to keep in mind that spammers frequently use Directory Harvest Attacks to try to guess recipient usernames at known domains. Thus, a domain may receive a large number of spam messages sent to nonexistent users, costing you server resources.

fail — Checks for the intended email recipient and, if no matching recipient is found, denies the SMTP request before downloading the message. This option is recommended.
blackhole — Discards the message after downloading it. This option uses system resources.
localuser — Allows users to set up their own catch-all email addresses. These email accounts will mainly serve to collect spam.

Reference :

Automatically create proxy subdomain DNS entries in WHM.

This can be enabled on the Tweak Settings page.

Enabling this option will allow WHM to automatically create DNS entries for the following 4 subdomains for every user’s account (where stands for the user’s domain):


These subdomains allow users to easily access the features included with a cPanel installation.

We can use /scripts/proxydomains to create DNS entries manually.


Problem importing one of the Python modules required to run yum

Error: There was a problem importing one of the Python modules required to run yum. … Cannot allocate memory.

Solution: Python frequently runs into the memory limits set inside WHM and cPanel. You may be able to resolve this issue by increasing the per process memory limit in the WHM Tweak Settings feature, or by running EasyApache from the command line to minimize its memory footprint.


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