RvKmR.blogspot.in

Hello Thanks for visiting RvKmR's blogs. So, What means of clusters and why we need them. Cluster is set of servers or say computers working together to achieve single goal or a task. Now you may have idea why we need cluster.  Types of Cluster: High Availability Cluster / HA Cluster  HA Cluster again grouped in two types. Active-Active Cluster Active-Passive Cluster In Active-Active Cluster Service is running on all nodes in cluster. That means all nodes serving independently. In Active-Passive Cluster Service is running on one of node from cluster and other nodes in passive state. If primary node fails then only other node in cluster will start service.   Storage Cluster In this cluster type, all members provides a single cluster file system that can be accessed by different servers. These file system can be used to read-write data simultaneously. EX: GFS2  OK, Then what is High Availability. This type of cluster provides ...

Hello, Thanks for visiting RvKmR.blogspot.in In this blog post, I am explaining about configuring passwordless ssh login. I setup two vms on vagrant environment, name and IP address of respective machines is listed below. I am using image "Ubuntu 14.04.5 LTS " alpha-ubuntu      10.0.0.10 beta-ubuntu        10.0.0.11 At this stage I am logged in to machine alpha-ubuntu. When I login from alpha-ubuntu to beta-ubuntu, it ll ask for password for respective logging in user. lets check it out. vagrant@alpha-ubuntu:~$ ssh beta-ubuntu The authenticity of host 'beta-ubuntu (10.0.0.11)' can't be established. ECDSA key fingerprint is 06:8d:d6:6d:a1:07:8e:19:2d:1a:2e:5c:b8:0a:0b:f5. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'beta-ubuntu' (ECDSA) to the list of known hosts. vagrant@beta-ubuntu's password: Welcome to Ubuntu 14.04.5 LTS (GNU/Linux 3.13.0-129-generic x86_64) Las...

Hello, Thanks for visiting RvKmR.blogspot.in In this blog post, I am explaining about Wheel users in Linux. Red Hat release that I am working on is as below.  [ravi@localhost vagrant]$ cat /etc/redhat-release CentOS release 6.9 (Final) An Linux system can have many users like System users, normal users, and admin (root) user. Its common sens that we have is not to share root user credentials with other user, but here is case that we wish to run administrative command by normal user. In that case we need to aware about wheel users group. Let's first understand what is wheel user in Linux and why we needed it. Wheel is one of Linux user group that allow members of that group to run administrative commands those need root access of system, Wheel user facilitate to do that with sudo (superuser do ) privileges. Lets do it on terminal : Add an user and set password [root@localhost vagrant]# useradd ravi [root@localhost vagrant]# passwd rav...

Hello, Thanks for visiting RvKmR.blogspot.in You may be curious about what happens in background when you press an power button of an Linux PC/server. Well in this post I am going to explain about how Linux systems boots. I gone thorough lot of tutorials and came with below boot steps. Before going to process you must to be aware of ROM, RAM, CPU etc.  OK, let's start !!! As soon as power button pressed system performs system integrity check, we call it as POST and load and execute boot loader to RAM. The module for performing POST and loading boot loader in RAM is available in ROM and which wont be lost when you power off the systems so that we call it as Read only memory. Then the cpu/processor comes in picture. processor having registers, some of them are AX, BX, CX, ISP etc. each of them having there own purpose. For now we are interested in ISP only, which is an instruction pointer in RAM. It means it holds address of instruction to run next. Loaded m...

Hello, Thanks for visiting RvKmR.blogspot.in In this post, I am going to explain about shebang line. We see many of script starts with #! special characters. We are aware of # as a comment but at the start of the script if we use #! then it is not an ordinary comment. It is an instruction to program exec which execute our script. The shebang #! is humanly readable instance of a magic number consisting of the byte string 0x23 0x21. This is passed to exec() to determine the file to be executed is a script or a binary. When shebang line #! is used exec runs the script with executable specified after shebang #!. Ex. #!/bin/bash This is an instruction to exec to start execution of the program with /bin/bash.

Hello, Thanks for visiting RvKmR.blogspot.in . In this blog, I am going to explain about my script for“Idera's R1soft CDP-agent installation ” written in bash. To understand this script you must be familiar with Bash scripting and Linux environment. Q   : I wan to install R1soft cdp-agent on clients server, but I don't have time to execute all commands manually.  OR  I am not familiar with Linux Operating System but I have to install R1soft CDP-agent on client server. Ans :   I have written bash script to install Idera's R1soft cdp-agent on Linux Operating System Launch Terminal with cltr+alt+T in ubuntu or from accessories menu in other Linux OS.There are some prerequisites needed before running this script. We need to know IP address or registered hostname of R1soft cdp-server. Below are steps to use R1soft cdp-agent deployment script: Download or copy r1soft.sh file to client/targeted server. Consider R1soft CDP-server ip address is :192.16...

Hello, Thanks for visiting RvKmR.blogspot.in . In this blog, I am going to explain about my script “Reset multiple Linux server password” written in bash. To understand this script you must be familiar with Bash scripting and Linux environment. Q   :  I have 100 's Linux server, I need to reset these Linux server password on weekly.  I know procedure to reset password of single server i.e. Login in to target server and reset password with utility “passwd”.  But here is issue : What if I have 100 's of server ?  it is not efficient way to login to each server and the reset password. Ans :     Written an bash script to automate this task. Details are mentioned below. There are some prerequisites needed before running this script. We need know targeted Linux server IP address and current password of server. Create a file “server_details”  at same location where is your main script located and write IP address and password like : "<I...