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This is going to make things very convenient when you need to install packages and you cannot find the ISO or the install media.

Or, when you want to install a package but there are dependencies and you cannot figure out which one to install first.

YUM makes it very easy. But what if your server do not have internet access?


Mount the OS ISO file.

Create "/apps/repository" folder.

Copy "<DVD>/repodata" and "<DVD>/Packages" to /apps/repository

Copy "<DVD>/media.repo" to "/etc/yum.repos.d" folder.

Update the  "/etc/yum.repos.d/media.repo" file as below.

You can unmount the ISO and will not need it anymore for installing packages.


Add lines below.




It will look like below.


name=Red Hat Enterprise Linux 6.1








Make this media.repo file read-only.


Then run "yum repolist"

It will return the following


[root@rhel61 Desktop]# yum repolist

Loaded plugins: product-id, refresh-packagekit, subscription-manager

Updating Red Hat repositories.

repo id                          repo name                                               status

InstallMedia               Red Hat Enterprise Linux 6.1                3,480

Repolist: 3,480

In SiteMinder documentation, it instructs to perform the following.


How to Prepare for the Policy Server Installation

(Red Hat Linux) The Red Hat operating system relies on entropy for performance. Increase entropy before installing the component. Without sufficient entropy, the installation can take an exceedingly long time to complete. Use the following commands:

mv /dev/random /dev/random.original
ln -s /dev/urandom /dev/random


When using /dev/random, if there is insufficient entropy it will be blocking until there is sufficient entropy while the /dev/urandom does not.

More info here.


What I usually do is, make use of the random number generator daemon instead.


# vi /etc/sysconfig/rngd


# Add extra options here

# Following means at every 5 seconds the entropy will be replenished to 4096

# Advice is to "cat /proc/sys/kernel/random/entropy_avail" every second to see how

# much demand there is for random numbers and adjust "-t" or "-W" to accommodate

# the demand

EXTRAOPTIONS="-i -o /dev/random -r /dev/urandom -t 5 -W 4096"

# service rngd start

# chkconfig rngd on


What above option does is, it will replenish a bucket of 4096 random numbers every 5 seconds.

And setting the service to start automatically.


Check how many entropy is currently available

          # cat /proc/sys/kernel/random/entropy_avail


Before this configuration change, there would usually be around 1000 during high and around 100 during low.


Note: (newer) Policy server installation may check for the symbolic link /dev/urandom as instructed in the documentation.

           In that case, you will need to follow the documentation to make the symbolic link otherwise the installation cannot continue.

           You can revert the configuration after that.


Windows Activation

Posted by SungHoon_Kim Employee Sep 10, 2015

After you deploy your sysprepped OVF image(Windows) to vSphere Hypervisor and after powering up it will ask you to activate the Windows.


What if you don't have the serial number handy?


No worries, just click "Next" and it will ask you if you would like to activate "current product key".

Click "Yes" and your Windows will be activated with the product key that you entered while you were installing the OS.




On Windows there is this SID that identifies objects uniquely.

When you fresh install a Windows OS, it will generate a random SID that should uniquely identify it.

The problem is, if you clone that image and try to promote one as a domain controller and have the other one to join this domain, you will get to an issue where the windows gets confused about who is who.


To prevent this, there was sysinternals utility called newsid.exe which will generate a new SID and apply it so you don't have to reinstall the OS again.

But this utility is no longer being provided.


So then there is this sysprep tool which can generalize your OS so when you boot up next time it will generate a new SID.

If you bought your new laptop and upon powering it on the first time you would have experienced it asking for your username and things and setup for you.

Sysprep does just that so it actually takes up some time until it is setup.


Once you have setup the OS, applied required patches, installed some apps and ready to make it a template, perform the following.


1. Open explorer and navigate to "C:\Windows\system32\sysprep" folder.

2. Run sysprep.exe



3. Check "Generalize" box.

4. Select "Shutdown" from dropdown options.


5. After it completes processing, it will shutdown.

6. Take a snapshot


Now you can convert this to OVF or clone this when you need a new machine.