Using the pipe backend in PowerDNS

PowerDNS is a Domain Name System (DNS) server with a lot of different possible backends, such as MySQL, PostgreSQL, LDAP, BIND zone files and a Unix pipe backend. In this article we will look at the pipe backend which is passed the DNS request by PowerDNS through standard input (stdin) and must reply through standard […]

Increasing the size of an LVM volume

In a previous article we looked at LVM. This short article describes how to grow an existing volume by adding an extra disk to the system. Specifically, we use a XenServer guest VM with CentOS installed. The first disk of a XenServer guest VM is called xvda, the second disk (the one we added) is […]

Using a Xen virtual machine image with Eucalyptus

In the previous article we created a CentOS virtual machine image that was usable with Xen. In this short article we will use this image in Eucalyptus. Bundle, upload and register the kernel with Eucalyptus: ec2-bundle-image –image /boot/vmlinuz-2.6.18-128.1.6.el5xen –kernel true ec2-upload-bundle –bucket centos-kernel-bucket –manifest /tmp/vmlinuz-2.6.18-128.1.6.el5xen.manifest.xml ec2-register centos-kernel-bucket/vmlinuz-2.6.18-128.1.6.el5xen.manifest.xml Bundle, upload and register the ramdisk with Eucalyptus: […]

Installing Ganglia on CentOS

In this article we will install the Ganglia monitoring system on a set of machines running CentOS. There are two kinds of machines involved: The meta node: one machine that receives all measurements and presents it to a client through a website. The monitoring nodes: machines that run only the monitoring daemon and send the […]

Installing Eucalyptus on CentOS

Setup Eucalyptus is software that enables you to run your own cloud. It aims to be API compatible with Amazon’s EC2, which means you can use most of the tools that are written for that system with Eucalyptus too. This articles describes my successful attempt at installing Eucalyptus 1.4 on CentOS 5.2 with managed network […]

Disabling default security on CentOS

Everybody wants their stuff to be secure, until they actually try to use it. That’s the reason for this tidbit about disabling the default security on CentOS. SELinux is enabled by default on CentOS. To disable it, we need to edit /etc/selinux/config: SELINUX=disabled We need to reboot the machine for this to take effect. The […]

Network configuration on CentOS

Static IP address Assigning a static IP address on CentOS is accomplished by editing the files in the directory /etc/sysconfig/network-scripts. For example, assign a static IP address to interface eth0 by editing /etc/sysconfig/network-scripts/ifcfg-eth0: DEVICE=eth0 BOOTPROTO=none IPADDR=192.168.0.123 NETMASK=255.255.255.0 GATEWAY=192.168.0.1 ONBOOT=yes Network interface bonding To achieve higher bandwidth and/or reliability, network interfaces can be bonded. First, edit […]

Enabling NTP daemon on CentOS

Here are the steps to take to enable the Network Time Protocol (NTP) daemon on CentOS. Change the timeserver value to one that is close to you. yum install ntp ntpdate nl.pool.ntp.org service ntpd start chkconfig ntpd on If you encounter the error “no server suitable for synchronization found”, you can use an unprivileged port […]