Using iptable’s LOG action certain things in the network tracffic can be logged. In this article I’ll explain how to log each and every minute network traffic using iptables. You can choose which Chain rules and tables should be logged. Information on network traffic is stored in /var/log/messages. This information can be very useful for debugging firewall rules or when you are configuring NAT.
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RHCE exam experience
In this article I’ll be sharing my experience of going through RHCE exam and a few tips on how to crack the one-of -the-kind performance based exams. Before I proceed let me tell you that I will NOT be sharing any exam questions because I’ve agreed to the NDA (Non Disclosure Agreement). For those who haven’t heard RHCE (Red Hat Certified Engineer) is a certification offered by Red Hat Inc. for which you have to pass two “performance” based exams, RHCSA (Red Hat Certified System Administrator) and RHCE. Performance based means you have to practically configure everything on the system they provide no objective type questions or theoretical ones where you can practice a couple of “dumps” and breeze through it.Continue Reading…
How to unregister RHN (Red Hat Network)
The RHN (Red Hat Network) is a service provided by Red Hat for receiving updates and support for your Red Hat Enterprise Linux installation. A RHEL copy can be added to RHN by executing the rhn_register command. If for some reason you want to unregister a machine from your RHN network login to RHN from http://rhn.redhat.com/ select you system and click “Delete System” located on the top right.
It isn’t over yet because your computer still “thinks” it is a part of RHN network. To unregister the computer a file has to be removed. Login as root user and execute the following command
rm /etc/sysconfig/rhn/systemid
if you aren’t comfortable with the command line open a file browser with super user permissions (root) navigate to /etc/sysconfig/rhn and delete the file systemid. You can execute rhn_register to reregister that system in future.
SSH verify host public key
Usually when you connect to a computer via SSH for the first time you might see a message stating “The authenticity of the host can’t be established Are you sure you want to continue connecting ?” even if you blindly give yes it has a lot of meaning in it. If you’re accessing your workplace computer through SSH just by entering ssh server.workplace.com you can’t be sure the connection is between you and your workplace server. A malicious user tampering with your internet connection can also create a man-in-the-middle attack and find out your Linux user account password. By importing the public key of the host to which you’re connecting you can be sure you’re “talking” to the right person.Continue Reading…
SSH configure key based authentication
Configure key based authentication in SSH to allow users to login without entering their password. Key based authentication uses public key cryptography to make sure only the owner of the correct private pair logs in through SSH. If the user logs in using password based authentication anyone knowing that user’s password can login. But with key based authentication only the person possessing the correct private key pair for the public key located on the SSH server can login. To add more security you can even add a passphrase to the SSH key.Continue Reading…
Forgot MySQL root user password (Linux)
Reset your MySQL root password if you ever forget it by following the instructions provided here. Earlier I wrote an article to reset the MySQL root password in windows, this article does the same thing in Linux resetting the MySQL root user’s password if you forget it. The instructions outlined here are based on the Linux command-line. The procedure is same for both Windows and Linux, stopping the MySQL service, creating an file with the SQL query to reset the Linux password and executing it through the init-file option.Continue Reading…
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