Configuring SNMPv3 client on Red Hat Linux

January 27, 2014
By Andrew Lin

To configure snmp client version 3 on a Red Hat server you will need to install the packages net-snmp-utils and net-snmp. yum install net-snmp-utils net-snmp Make sure the snmpd service is stopped before you can configure it. service snmpd stop Create a new SNMPv3 user called “andrew”. The authentication password is “auth-pass” using MD5...
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Add new disk to Red Hat Linux server, create new filesystem without reboot.

January 27, 2014
By Andrew Lin

If you are running a VMware virtual Red Hat Linux server then it is very easy to add a new disk. For physical servers with hot add capability this is also possible. I am going to show you how to add a new disk...
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VMware converting RAW disk to VMDK

August 28, 2013
By Andrew Lin

Convert a Vmware RDM disk to VMDK while guest VM is powered off Power down the guest VM Clone the VM, under select virtual disk format – select Advanced – change the disk format to Thick provisioned. You only need to do this step...
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Expanding VMware virtual IDE disk for Windows XP

November 30, 2012
By Andrew Lin

In VMware ESX 4.x the default disk type for Windows XP 32bit virtual machine is IDE. If you did not size your drive correctly, you will be unable to expand this virtual disk later using the VMware management client. But if you had selected...
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Script to power down many Windows servers

November 14, 2012
By Andrew Lin

If you ever have the need to power down hundreds of Windows servers, then here is a script to do just that. This script will work for Windows 2000, 2003 and 2008. The servers will shut down gracefully. for /F %%a in (names.txt) do...
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Configure the DVD or Linux ISO as software repository for Red Hat Enterprise Linux

September 7, 2012
By Andrew Lin

You downloaded and installed Red Hat Enterprise Linux on your server becasue you just want to test it out. During installation you selected base server, after installation you realize that you need to install additional packages. But since you did not purchase the Red...
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SSH Login without password using public key authentiation

August 23, 2012
By Andrew Lin

On Computer A Create the public and private keys using the command ssh-keygen # ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification...
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How to extend the filesystem on a Vmware ESX guest Red Hat Linux server

May 26, 2011
By Andrew Lin

Being the administrator of a large Linux shop, I have had to extend the filesystems on the Red Hat Linux server a few times. Each time I had the opportunity to extend the filesystem, I found that I struggled to remember the commands and...
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Unable to login to remote server via ssh

May 18, 2011
By Andrew Lin

A funny thing happened to one of my Red Hat 5 Enterprise servers after applying the errata. I rebooted the servers as usual after applying the updates, and they came up just fine. But unfortunately I was not able to logon remotely via ssh...
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How to create a new superuser in Linux

May 17, 2011
By Andrew Lin

The administrative account ‘root’ is the most powerful user in Linux and Unix. This account is created by default during installation of the operating system. Most security consultants will recommend that the root account be deleted or renamed. This is to make it harder...
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Troubleshoot problem with yum update and rebuild the rpm database

March 15, 2011
By Andrew Lin

I have created a step by step approach to troubleshoot a problem with performing yum update and how to rebuild the rpm database. I received and error while trying to update the Redhat Enterprise 5 server kernel using yum update. Looking at the output...
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Booting Red Hat Linux into rescue mode.

January 28, 2011
By Andrew Lin
Booting Red Hat Linux into rescue mode.

Red Hat Linux can be booted into rescue mode from the installation CD, or any other boot method instead of the system’s hard drive. This also applies to other versions of Linux such as Fedora and Centos. The rescue mode is provided for troubleshooting...
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Identifying the kernel version and changing the default boot kernel in RedHat and Centos Linux.

January 27, 2011
By Andrew Lin

Use the command uname to print system information in Linux. # uname -r 2.6.18-194.32.1.el5 The –r option will print the kernel release. # uname -s Linux -s prints the kernel name. # uname -n mycomputer.wiivil.com Print the node name or hostname. # uname -p...
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Nslookup resolves address but ping is unable to resolve hostname on Unix server

November 17, 2010
By Andrew Lin

I came across this issue on my newly built Solaris 10 server. I was able to ping a remote machine by Ip address, but not by its hostname. This indicated that I had the correct route and gateway. Using nslookup and dig I verified...
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How to map to a remote NFS directory from a VMware ESX 4 server.

November 16, 2010
By Andrew Lin

I ran into this error while trying to mount a NFS directory on a remote server from my Vmware ESX4 server. My Vmware esx server is called esx4-server and the remote NFS server is called remote-server. I executed the mount commant and got the...
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