Replication…..

Flawless replication of a linux box is one of the greatest advantages of linux. Here’s an overview on how to get it done. But why would one want to replicate a linux box?

Reason 1: If you have bought new PC and want to move the same OS and all those custom settings onto the new one.

Reason 2: If you feel that your hardware is acting funny and may fall apart any moment, depending on the moment this could be a backup scheme.

Reason 3: Having the same exact OS on 2 machines would meant if I had to update 1 machine I wouldn’t have to download the packages again to update the other one (well with thin and expensive internet pipes, it would definitely mean something).

Reason 4: When the need arises to do similar installations on a large scale.

I want to say that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take.

What would one need to do this?

Requirement 1: A live CD with good hardware detection abilities. Something like Knoppix or others like System Rescue, Helix etc.

Requirement 2: If you do not want to open up any of the machines the replication job can be done over a network (well I definitely prefer this, because the warranty holds good on a new PC). Then atleast a cross cable and LAN cards on both the machines is a must.

Be certain that the OS being cloned should not be too old to the hardware you wish to clone it on. Example if the OS has a 2.4 kernel probably the usb controller will have no support or the X server will refuse to start because the graphics card or tft monitor could not be identified. For reasons such as this its very much important to keep the OS updated.

I’ll be calling the machine being cloned “A” and the other “B” and both these machines will be cloned over a network.

Boot machine A with its existing OS and boot machine B with the Knoppix live CD preferably in runlevel 2 by issuing “knoppix 2” at the start-up screen. If the machine B has not more than 64Mb ram, the recent versions of Knoppix will refuse to boot. In that case use an older version of Knoppix say in the 3.x series.

Set appropriate IP addresses on both the machines and ensure that ssh works between the 2. example, 192.168.0.1 on A and 192.168.0.2 on B and both having sub-net mask of 255.255.255.0

Check the disk usage on A and create partitions on B. Here I would recommend creating a separate /boot partition maybe of 100Mb size.

Use the “mkfs.ext3 -O none /dev/hdax” command to create the file-system.

I’m using the “-O none” option here because the version of Knoppix I’m using is the latest while the OS on machine A is pretty old. The ext3 file-system has had a number of changes over the years. The machine may probably never boot without this option.

Do not forget to create the swap partition and format it using “mkswap /dev/hdax”.

mount the first partition on B, example

# mount /dev/hda1 /media/hda1

in my case this was the /boot partition.

# rsync -Pax –numeric-ids -e ssh root@192.168.0.1:/boot/ /media/hda1/

Do this for every partition.

Mount the partition on B that contains the /etc/ directory and edit the fstab file accordingly. also edit the modules.conf/modprobe.conf if you are sure which modules will be used on B.

If your boot and / partitions on B are different from that on A, do not forget to edit the grub.conf or menu.lst file for grub to boot the machine properly.

The last step would be to install grub on the master boot record or the active primary partition. To do so, firstly unmount the boot partition that’s mounted on /media/hda1 and mount it on the /boot of the knoppix cd.

#umount /dev/hda1

#mount /dev/hda1 /boot

# grub-install /dev/hda OR

#grub-install /dev/hdax (the primary active partition)

Reboot the machine without the Knoppix live CD. Boot into the single user mode the first time. If you have replicated a Redhat based distro something like kudzu will guide you through hardware changes detected. If its a Debian based distro once you have booted issue “update-modules”.

That’s it. Simple isn’t it? I’m sorry for my terrible writing but like I said before its just an overview.

Let me say that I’m truly overwhelmed by the responses to my previous postings. It would be simply superb if all of it could be as comments on this blog rather than mails to me. Thanks a million.

Advertisements

Leave a comment

No comments yet.

Comments RSS TrackBack Identifier URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s