• RANCID Homepage
• How to set up and use RANCID under CentOS

Memory Balloning is a memory reclamation technique employeed by VMware ESXi hosts, that is triggered by high memory utilization on the host and aims to reclaim unused memory on some VMs, for use in others that require it.

Read more

• VMware Memory Management Part 3 - Memory Ballooning
• VMware Ballooning Explained

This is a list of acronyms that I come across while reading VMware documentation.

TPS

Transparent Page Sharing is a memory-saving technique that runs as a background job on the host, and deduplicates the contents of RAM on the hypervisor, page by page. Read more on TPS...

A series of articles at the MySQL Performance Blog on MySQL Fabric:

1. Managing farms of MySQL servers with MySQL Fabric
2. High Availability with MySQL Fabric: Part I

Apache's mod_log_config module (installed by default on CentOS 6) allows for the CustomLog directive, which in turn takes a log format specification. This post shows how to use ISO format for Apache logs.

• How to verify DDOS attack with netstat command on Linux Terminal

To better organize your source code in a web.py application, you can break it down in subapplications. Those subapplications will be imported as Python modules in your main web.py script (which, in the below examples is index.py).

Troubleshooting

AttributeError: 'module' object has no attiribute ...

If you get the error:

AttributeError: 'module' object has no attribute 'app'

...then you might be running into Python naming collissions. Check if you have given one of your subapplications the same name as an existing Python module. For example, you shouldn't name a subapplication user, since that is an existing Python module.

ImportError: No module named ...

If you get the error:

ImportError: No module named subapp

... (where subapp is the name of your subapplication), then Python cannot import the subapplication as a module. As a first step, create an empty file named __init__.py in the same directory as your subapplication, and try again. If you still get that error, and assuming your subapplications are in the same directory as your main application, you can try this ugly hack in the very beginning of your main application script:

import inspect
import os
import sys
sys.path.append(os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe()))))

• Using sysdig to Troubleshoot like a boss
• Sysdig + Logs: Advanced Log Analysis Made Easy
• SysAdvent 2014, Day 3 - So Server, tell me about yourself. An introduction to facter, osquery and sysdig

Sometimes you need to create a test database on a development MySQL server, to run some tests on, and you want to populate it with many records, to make your tests more meaningful. This document lists a couple of quick and dirty ways that I use to achieve that.

Using /usr/share/dict/words

On most Linux distributions, there is a file at /usr/share/dict/words which contains a list of words, each on a separate line. On my Linux Mint 15 installation, I count more than 99000 lines. The following commands will put those words in a table called words, in a database called test, one word per table row.

Create the table:

mysql> CREATE TABLE words (id INT AUTO_INCREMENT, word VARCHAR(256));

Populate the table with the words. I 'm using double quotes to wrap the words, since many of them already contain a single quote:

while read word; do mysql test -e "INSERT INTO words (word) VALUES (\"$word\")"; done < /usr/share/dict/words

Using /var/log/messages

I have also used the contents of /var/log/messages to populate a table, and that is documented in the blog post How to create a large MySQL database for tests. That is a painfully slow method, but can create tables that are many GigaBytes in size, which might be necessary for some tests.

• zentyal.org

See Also

This is a series of articles for setting up a network with Zentyal acting as the Primary Domain Controller, published at tecmint.com:

1. Install Zentyal as PDC (Primary Domain Controller) and Integrate Windows System
2. How to Manage Zentyal PDC (Primary Domain Controller) from Windows System
3. Creating Organizational Units (OU) and Enabling GPO (Group Policy) in Zentyal PDC Server
4. Setup File Sharing and Permissions for All Users in Zentyal 3.4 PDC
5. Integrate Ubuntu System in Zentyal PDC (Primary Domain Controller)
6. Integrate CentOS/RedHat/Fedora in Zentyal PDC (Primary Domain Controller)
7. Integrate Ubuntu 14.04 (Trusty Tahr) to Zentyal PDC (Primary Domain Controller)
8. Installing FTP Server and Mapping FTP Directories in Zentyal PDC
9. Install and Configure Web Services (Apache Virtual Hosting) on Zentyal Server
10. Enabling UserDir and Password Protect Web Directories on Zentyal Webserver
11. Installing Pydio File Sharing Platform on Zentyal 3.4 Webserver
12. How to Install and Configure OpenVPN Server on Zentyal 3.4 PDC
13. Install and Configure Zentyal Linux 3.5 as A BDC (Backup Domain Controller)
14. Joining CentOS 7 Desktop to Zentyal PDC (Primary Domain Controller)

Articles for Zentyal 3.5, released on July 1st 2014:

• Install and Configure Zentyal Linux 3.5 as A BDC (Backup Domain Controller)