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Getting the very best return on your IT investment with GNU/Linux.

Getting the very best return on your IT investment is not always straightforward, and that's where the Linux Community can be of help.

Did you know: Linux source code for all supported architectures is contained in about 4500 C and Assembly files stored in about 270 subdirectories; it consists of about 2 million lines of code, which occupy more than 58 megabytes of disk space.

Linux is a tiny operating system when compared with other commercial giants. Micro$oft Windows 2000, for example, reportedly has more than 30 million lines of code. Linux is also small when compared to some popular applications; Netscape Communicator 5 browser, for example, has about 17 million lines of code.

One of the more appealing benefits to Linux is that it isn't a commercial operating system: its source code under the GNU Public License is open and available to anyone to study, the official site is http://www.kernel.org/

The GNU project is coordinated by the Free Software Foundation, Inc. (http://www.gnu.org/); its aim is to implement a whole operating system freely usable by everyone. The availability of a GNU C compiler has been essential for the success of the Linux project.

GNU/Linux provides robust & scalable platform for changing business.

In some ways, Linux is the champion of a set of ideals. Whether you buy into these ideals is a separate issue from whether you use the technology, of course, but nonetheless a complete understanding of Linux and Linux-based systems requires at least an awareness of the legacy.

  • The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software: the GNU operating system.
  • Unix-like operating systems are built from a collection of libraries, applications and developer tools, plus a kernel to allocate resources and talk to the hardware

GNU+Linux is an operating system, but it's also representative of a lot more.

Linux-based operating systems are extremely powerful and flexible, but unlocking that power and flexibility requires knowledge and understanding of how the system works. Note:Linux is "merely" a kernel. That is, Linux is a piece of software that manages resources and processes, but provides no system libraries or user interface.

Since Linux is just a kernel, it requires a set of system libraries to become a useful environment. If Linux is just a kernel, where do these system libraries come from? Who writes them? Who maintains them? Obviously, whoever maintains these libraries makes a huge contribution to Linux systems in general. In the vast majority of Linux installations, the system libraries are the GNU utilities, written and maintained by the Free Software Foundation.

Linux Tips and Faq Articles

Setting up your first LAMP server on Ubuntu.

You can use apt-get to install these packages by running the following commands: 

sudo apt-get install apache2
sudo apt-get install php5
sudo apt-get install php5-cli
sudo apt-get install php5-cgi
sudo apt-get install php5-mysql
sudo apt-get install php5-pgsql
sudo apt-get install libapache2-mod-php5
sudo apt-get install build-essential
sudo apt-get install mysql-server
sudo apt-get install mysql-doc-5.0

Linux Kernel recompilation with GRSECURITY

To recompile the Linux kernel, Upgrade to at *least* these software revisions before thinking you've encountered a bug! If you're unsure what version you're currently running, the suggested command should tell you.

Grsecurity is an innovative approach to security utilizing a multi-layered detection, prevention, and containment model.

It is licensed under the GPL. more details at Linux-Kernel-recompilation-with-GRSECURITY

iptables linux firewall for home office networks.

The below example has the follwoing settings. 

# Internet Interface
INET_IFACE="ppp0"
# Local Interface Information
LOCAL_IFACE="eth0"
LOCAL_IP="192.168.1.1"
LOCAL_NET="192.168.1.0/24"
LOCAL_BCAST="192.168.1.255"

More - iptables-linux-firewall-for-home-office-networks

Requirements for Nagios Notifications.

If you want to receive email notifications for Nagios alerts, you need to install the mailx (Postfix) package. 

sudo apt-get install mailx
sudo apt-get install postfix

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favorite editor and change the email address associated with the nagiosadmin contact definition to the address you'd like to use for receiving alerts. You'll have to edit the Nagios email notification commands found in /usr/local/nagios/etc/objects/commands.cfg and change any '/bin/mail' references to '/usr/bin/mail'. Once you do that you'll need to restart Nagios to make the configuration changes live.

Requirements-for-Nagios-Notifications

Planning your Linux partition structure.

For a less simple partition structure: 

/boot    60-100 meg 
swap     2 x memory
/tmp     1 Gig. mount /tmp with noexec,nosuid in /etc/fstab
/        6-10 Gig
/var     8-20 gig. Emails, logs and databases stored here
/usr     5-12 gig. source code
/home    rest of drive. Roughly 80% for user data. 
/home    Mount with nosuid in /etc/fstab if possible.

Feel free to modify these numbers as needed. Note, if you plan on installing dovecot, all email data is stored under /home and not /var, so adjust as needed. Also FreeBSD store mysql databases in /home/mysql/. Please have Basic development/compiling tools such as gcc, g++, and perl.

Working with LVM Logical Volume Manager

  • Creating hard drive space into logical volumes.
  • Since physical volumes cannot span over more than one drives.
  • /boot partition cannot be a lvm because the partition cannot be read by the boot loader
  • /boot should be on a separate partitions. - ext3
  • lvm2 uses the device mapper driver in the kernel 2.6
  • First create PV -physical volume, then create volume group-VG, and then the logical volume-LV.

More - LVM-Logical-Volume-Manager

How to verify signature of downloaded source file with GPG

Here downloaded file is postfix-2.6.5.tar.gz and the signature is postfix-2.6.5.tar.gz.sig 

$ gpg --verify postfix-2.6.5.tar.gz.sig postfix-2.6.5.tar.gz
gpg: Signature made Sat Aug 29 00:50:08 2009 UTC using RSA key ID C12BCD99
gpg: Good signature from "Wietse Venema <[email protected]>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: FF 96 4A 8C 96 88 7C 6E  A4 EF AD BF 48 34 E1 BB

More - how-to-verify-signature-of-downloaded-source-file-with-gpg

namp scan techniques host discovery version detection and much more

ubuntu@mail:~$ man -k nmap
nmap (1)             - Network exploration tool and security / port scanner


Nmap 4.53 ( http://insecure.org )
Usage: nmap [Scan Type(s)] [Options] {target specification}

More -namp-scan-techniques-host-discovery-version-detection-and-much-more

Using perl to make changes to a list of files.

Example below add comment to all the virtual host conf file in apache. 

perl -pi -e 's/Error/#Error/' virtual_host*.conf

perl -pi -e 's/ssl=ON/ssl=OFF/' /usr/local/directadmin/data/users/*/domains/*.conf

CentOS 5.4 rpms list download page.

http://mirrors.kernel.org/centos/5.4/os/i386/CentOS/

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