Author: Surendra Anne

DNS Troubleshooting in Linux

Posted by | May 29, 2009 | |

Some basic DNS troubleshooting in Linux. First collect the information which has created the problem by doing some investigation(such as logs, debug messages etc) . Prepare your tools which is required for your troubleshooting. Troubleshooting is nothing but considering so many issues that may cause the problem and working one by one to pin point the actual culprit which created the issue. once issue is pin-pointed you have to work on that issue with the tools/commands/logs all other resources and have to resolve it. Coming to troubleshooting DNS aka named services, here are the steps how we can resolve the DNS related issue: I will take one scenario “suppose my client is unable to resolve host-names to IP address” Step1:Check the DNS server is configured on Client end or not check in below file if name server is configured to proper DNS server or not#vi /etc/resolv.confIf the client is configured with proper DNS server follow to next step Stpe2:Ping to DNS server ip address #ping serveripadd If pinging is happening proceed with the next step other wise click here to do network troubleshooting. Step3:So pinging is happening… then there is a communication path between Server-client, so we have to check weather DNS server is running or not. Here nmap can be used to check what ports opened on server. #nmap serveripadd Example:#nmap 125.22.73.23 this command will give you output...

Read More

Recovering Ubuntu Grub bootloader

Posted by | May 27, 2009 | |

I was having trouble with Windows and I installed Ubuntu on my laptop. Unfortunately I re-installed windows after Ubuntu and now I don’t have the option of viewing the boot menu to select Ubuntu. I was using the dual boot mode. Is there a way to view the boot menu in Windows XP that will allow me to select Unbuntu again? This is some what tricky question, acutually when you install Ubuntu the bootloader “GRUB” will take care of MBR(Master boot record) and boot menu details such as OS’s present either it’s a linux/nix or windows, because GRUB is a universal bootloader which will understand most of the OS’s. But it is not the case with Windows bootloader boot.ini which cant not understand other then Windows, So when you reinstall windows after Ubuntu, the Windows OS will rewrite the MBR and bootmenu with it’s own parameters. So your system doesnot know where Ubuntu/linux is located To resolve this issue just use Ubuntu live cd and reinstall GRUB boot loader. If you are using Redhat and windows follow below procedureStep1 : Insert the first cd of your linux and boot from cd. Step2 : Start with linux rescue method. Step3 : Mount the partitions via chroot. then install grub through #grub-install /dev/hdcStep4 : rebootnow u will get GRUB loader and your Linux will be rescued. Please visit https://www.linuxnix.com for more...

Read More

Login Problems

Posted by | May 25, 2009 | |

Login Problems When a user/root try to login to Linux system there are so many problems which will prevent the root/user not to login. Here we will see what are the problems which will prevent user from not to login to system and try to resolve them one by one. We can divide these problems in to two categories: Physically present at system. Accessing system from remote location(through network). Logging in to the system when you are present infront of the system. Issue1:Check weather the password you are typing is correct or not, what I mean is Case sensitive etc,here I am considering that you forgot the password for that system, In this case follow these steps Issue2:Still not able to login to system except runlevel1, so how to resolve this issue? Check root user properties such as shell type, age and security etc? Step1 : Check the root properties by using finger command.#finger rootLogin: root Name: rootDirectory: /root Shell: /sbin/nologinNever logged in. this command will give you the properties of the root user, here we have to check what is the shell he is using, the shell should not be nologin shell. If the shell for the root user is no login shell he will not able to login to system so we have to change the login shell from /sbin/nologin shell to some other shells such as...

Read More

Over 16,000 readers, Get fresh content from “The Linux juggernaut”

Email Subscribe

Take this course

Essentials of OpenStack Administration (LFS252)

ABOUT ME..!

My photo
My name is Surendra Kumar Anne. I hail from Vijayawada which is cultural capital of south Indian state of Andhra Pradesh. I am a Linux evangelist who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. At present I work at Bank of America as Sr. Analyst Systems and Administration. You can contact me at surendra (@) linuxnix dot com.