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Showing posts from March 10, 2013

Allowing users to have ssh access

Allowing users to have ssh access Hi Readers, It is one of the tasks we need to complete in order to allow users to log-in into your server without compromising your security. We are going to accomplish the following tasks, 1.) Allow the users for given domain only 2.) Must allow access to a given domain 3.) Block access for a specific domain. These questions are asked in RedHat certification examination RHCE6 We are going to complete the above mention task using iptables To give proper example we are taking 192.168.20.0/255.255.255.0 as our domain and 192.168.21.0/255.255.255.0 as other domain. Assuming that your system is a fresh installation we can remove all rules previously applied. # iptables -F  The above mention command will flush all the previously applied rules. Insert a rule in your input chain by below mention command, # iptables -I INPUT -s <ip of your domain>/<subnet mask> -p <protocal tcp/udp> --dport <port> -...

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Hubot and Hipchat

Many of us have struggle with concept of L1, and L2 support and maintenance which can be very expensive and transitioning is a living hell. What we wish is the ability for both of them to work together and make a smooth transition. So I have started to think it would be cool to make this happen for a organization which runs 1200+ servers and have teams to support product and infra both. The Idea was to start with collaboration between teams which can be extended to request and support basis. To extend it further we discovered  that product team works for 24x7 and infra team is 18x7. Now it is important to design it in a way that product team can manage it 24x7 with minimum and no help from infra team(L2).  Solution: Solution was to use a collaboration tool which supports API for our tools to maintain alert level. For that please refer my previous blog describing configuration of Icinga and Hipchat. Next logical step is to configure hipchat to support robot system ...

Read a File line by line in Shell

I've used a few techniques for this kind of reading but gets failed until I've read this fine blog . http://www.bashguru.com/2010/05/how-to-read-file-line-by-line-in-shell.html this helps a lot and i have developed a trick for me. Refer to the following example to examine the script : #!/bin/bash #SCRIPT: method2.sh #PURPOSE: Process a file line by line with redirected while-read loop . FILENAME=$1 count=0 while read LINE do let count++ echo "$count $LINE" done < $FILENAME echo -e "\nTotal $count Lines read" I have passed the file in the end of the loop so i didn't need  to use pipe that is why i process the file in fastest manner and gives  the required output in a quick manner. However i can use one more thing the File Descriptors. The File Descriptors are similar to the normal file pointers however in  more analogue way.If you have used C then you will have familier with the  the default file openers in C "st...

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