Debian

In addition to the considerations for High Availability clusters, more tightly coupled environments such as Beowulf clusters also require an infrastructure to manage and distribute computing tasks. There are several web pages devoted to creating a Beowulf cluster using Debian as well as packages that aid in creating such a cluster. One such page is https: / /wiki. debian. org/StartaBeowulf, a Debian Wiki page on Beowulf basics. The manual for FAI, mentioned previously in configuration management, also has a section on creating a Beowulf cluster. Books are available as well.

Some common components of clusters have already been mentioned, such as the OpenMPI libraries. Aside from the meta-packages already mentioned, the redhat-cluster suite of tools is available in Debian, as well as many useful libraries, scheduling tools, and failover tools such as booth. All of these can be found using apt-cache or Synaptic by searching for "cluster".

Many administrators will never have to administer a cluster, and many won't be responsible for a large number of systems requiring central backup solutions. However, even administering a single system using command line tools and text editors can be a chore. Even clusters sometimes require administrative tasks on individual systems. Fortunately, there is an application that can ease many administrative tasks, is easy to use, and can handle many aspects of Unux administration. Itis called Webmin.

Webmin may be installed by adding the following lines to your apt sources file:

deb http://download.webmin.com/download/repository sarge contrib deb http://webmin.mirror.sornersettechsolutions.co.uk/repository sarge contrib

Usually, this is added to a separate webmin.list file in /ete/apt/sourees .list.d.

The use of 'sarge' for the release name in the configuration is not a

Webmin runs in the background, and provides an H1TP or H1TPS server on localhost port 10,000. You can use any web browser to connect to http:// loealhost: 10000/ to access Webmin. Upon first installation, only the root user or those in a group allowed to use sudo to access the root account, may log in but Webmin users can be managed separately or in conjunction with local users.

Webmin understands the configuration file layout of many distributions. The main problem is when a particular module does not handle certain types of configuration in the way the Debian developers prefer, which can make package upgrades somewhat difficult.

Security is always a concern when remote access to a system is involved. Webmin handles this by requiring authentication and providing for detailed access restrictions that provide a layer of control beyond the firewall. Webmin users can be defined separately, or certain local users can be designated. Access to the various modules in Webmin can be restricted to certain users or groups of users, and detailed logs of Webmin actions are kept.

In addition to Webmin, there is a server called Usermin which may be installed from the same repository as Webmin. It allows individual users to perform a number of functions more easily, such as changing their password, accessing their files, read and manage their email.andmanagingsomeaspectsoftheiruserprofile.Itis also modular and has the same security features as Webmin.

Several powerful and flexible central backup solutions exist that help manage backups for multiple remote servers and sites. Debian provides packages that assist in building High Availability and Beowulf style multiprocessing clusters as well. And, whether you are involved in managing clusters or not, or even a single system, Webmin can ease an administrator's tasks.

Two primary functions are required to implement a high availability cluster: