This article explains what is a Digital Signature, why it is an important part of the Digital Identity, and how it works. Then it describes the authenticity and social problems related to the usage of the Digital Signature. It explains as well the two authentication models, X.509 and OpenPGP, that can be used to solve these authenticity problems. Finally it makes a comparison between these two authentication models and their features and tries to explain why the OpenPGP model is better.
Thursday, August 30, 2012
A powerful rack server can be used as a host for installing lots of virtual machines, and it can be used as a data storage as well. This article will describe how to use such a server, installed with CentOS, as a host for virtual machines.
Tuesday, August 28, 2012
Thursday, August 23, 2012
Recently I purchased a virtual ubuntu server on rackspace. However I have to manage it myself, and this includes first of all taking care for its security. Securing it is very important and is the first thing to be done, since all the rackspace servers have public IP-s and so are open to all the possible attacks from the Internet. Here I will describe some of the steps that can be done to secure the server.
Wednesday, August 22, 2012
I have used zentyal as a gateway server, and it is actually running on a virtual machine. An important component of it is squid, which is supposed to improve the efficiency of the network connection by saving in cache the web pages that have been already visited, and fetching them from the cache when they are re-visited.
This is an operation that makes intesive usage of the disk, and virtual disks (used on virtual machines) are not particularly efficient for it. However, a virtual machine can also use a real partition, so the efficience of squid can be improved by attaching a real partition to the virtual machine and using it for the cache.
Monday, August 20, 2012
Sunday, August 19, 2012
Thursday, August 9, 2012
We have about 40 computers installed with Edubuntu, and more than a dozen of servers (most of them running on virtual machines). They all need to be updated time after time with the latest version of packages. Also, time after time, new packages need to be installed. These packages come from some central Ubuntu Repository servers.
All this activity for keeping computers up-to-date (up to the latest version) consumes lots of bandwidth and takes a lot of time. And there are new package updates almost every day! For one computer this can be acceptable, however for lots of computers it may become unbearable.
One solution for this problem is to create a local mirror of the ubuntu repository.