Tricky question: What protocol (TCP or UDP) DNS server uses when a client queries?

By default DNS server will serve all client queries with UDP protocol on 53 port. One reason for this selection of protocol is to get faster answers from DNS Server to the client. The UDP protocol do not require any handshake like TCP before the connection establishment. Many people new to Linux do not know(…)

Domain Name Server(DNS) Evolution

History of DNS server How DNS server evolved? To understand why we require DNS server we have to go back to initial stages of networking the computers around late 1960’s and early 1970’s where it all started in Universities(especially Barkley University). Initially there is single computer for university due to cost and other factors, then(…)

How to stop and remove/uninstall SSH server from Linux

How to uninstall SSH server in Linux Redhat/Ubuntu? Some times you in order to make your system more secure you want to stop unwanted service and remove them permanently so that your machine is not compromised. Such service include SSH, FTP etc which should be uninstall if they are not used. In this post we(…)

Up coming posts on DNS(Domain Name System/Server) in Linux

We are very much happy to announce that we started posting on DNS client and Server stuff on our blog for this month(Jan 2011). We already have some minor existing stuff related to DNS and troubleshooting it. Below are quick links to our existing DNS Server/Client stuff Some of the DNS topics which are going(…)

How to change Apache port in Linux/Unix

Q. Change the port number of Apache web server in Linux and Unix? When ever a network service is started it starts listening on particular port. For example DNS server listen on 53 UDP and TCP port and Telnet server listen on 23 port. For more service and port mapping for different Linux service please(…)

How to install sendmail

This is a small post on how to install sendmail in Linux Sendmail is a mail server package which most popular mail server(but not a secure and easy to configure server). Installing sendmail package. #yum install sendmail #yum install m4 Note:See our other how to on configure local YUM server. m4 package is to compile(…)

How to check a service is running or not in Linux?

This is a small "How to" for checking a service is running in the server or not. Some times we need to check the status of a service if it is running or not to cross verify something on server. Suppose you have edited your httpd.conf file and when restarting the service it just show start(…)

How to mount FTP share locally in Linux using ftpfs

Q. I want to transfer one latest file from my ftp server share and I want to automate this task through shell script to download latest file from my FTP server, And I don’t know what is the Operating System at server end(This is ultimate sentence I hear from the user today in my office(…)

The scheme was not recognised as a valid LDAP URL scheme.

When you are configuring Apache-Aactive directory integration you may find this error. This is bit strange error, this type of errors will come when the LDAP URL is not mention properly. There may be a special character in the line which you coped from some file/doc/blog causing this issue. If you see below lines both(…)

How To Add Subdomain(Subzone) DNS Record In Linux?

Recently we got a requirement to configure a Sub-domain(sub-zone) record in DNS server.  Its little bit advanced concept but very much easy to configure. The most known records are as follows. A record for Adding an IP address record NS record for a Name Server record PTR record for a pointer record( i.e. Reverse IP(…)