GPG error: lucid Release: The following signatures were invalid

If running 'apt-get update' you get the error:

Reading package lists... Done
W: GPG error: lucid Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key


cd /var/lib/apt
mv lists lists.old
mkdir -p lists/partial
apt-get clean
apt-get update


How to remove/turn off/disable Linux KVM virbr0 NAT Interface

A virtual bridge, can be defined as a device that bridges virtual interfaces. It provides an easy means of networking virtual networking devices such as venet (virtual network) or veth (virtual ethernet).

How to optimize Apache for performance memory usage

1. SSH into your server as root.
2. Run top.
3. Press shift + m.
4. Note the highest RES memory used by httpd.
5. Hit Q to exit top.
6. Execute: service httpd stop
7. Once httpd is stopped, execute: free -m
8. Note the memory listed under "used".
9. Find the guaranteed memory for your VPS plan. Support can tell you how much you have guaranteed if you cannot find it.
10. Subtract the memory USED from the memory that your plan is GUARANTEED. This will give you your base FREE MEMORY POOL.

Best APC settings for a Drupal site to reduce page execution time

This is one of those "how long is a piece of string questions".

What is good for a high-volume site may not be the same for a low-volume site with a lot of modules, and may not be the same for a medium-volume site with only a few modules enabled. Other sites running on the server may also be eating into the memory that APC has available.

My starting point is


Enable log files

MySQL provides many different log files to capture various information that you can use for performance tuning or during problem determination.

To enable the log files, do the following:
Create the /etc/my.cnf options file with the following definitions that enable the log files automatically:


By default, the logs are placed in the data directory /pathname/mysql/data. The log names default to the name of the host system followed by a log identifier such as -bin.


How and where to set administrator's e-mail in Apache

If your system was not configured with administrator e-mail then on 500 Internal Server Error you will see the following message:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, [no address given] and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

To set admin's e-mail open:

How to install memcached on Ubuntu for use with Drupal

This guide is based on various community forum posts. Special thanks to Jonathan Wagener for the Ubuntu specific instructions

Monit configuration to monitor Memcached instances

Monit is a free open source utility for managing and monitoring, processes, files, directories and filesystems on a UNIX system. It is pretty easy to configure and even easier to use. It comes with a simple web server to monitor statuses of the alerts you set (with basic HTTP authentication). On Monit W’k’ you can find configuration examples for different services. Just in case you need a configuration example for Memcached instances, here is what you need.

How to properly install drush on Ubuntu 10.04

Despite it is clearly noted on the recommended way is to download Drush from the project page and to install it manually by reading the instructions of the README.txt file, many people start executing the aptitude command given on the same page:

$ sudo apt-get install drush

and the subsequent commands like

$ drush --version
$ drush dl drush

give you no joy since the official Ubuntu repositories contain very much outdated version of drush, which can not neither update itself nor display its version.

Monit mysql monitoring problem with missing

Monit is a nice tool, it lets you monitor daemons like apache and mysql, and not only sends you alerts when these services fail but also it automagically restarts those services. But I have always faced problem with having monit properly detect whether mysql is running or not. The default monit config file /etc/monit/monitrc has this entry for mysql:

check process mysql with pidfile /var/run/mysqld/
group database
start program = "/etc/init.d/mysql start"
stop program = "/etc/init.d/mysql stop"
if failed host port 3306 then restart


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