I downloaded centos everything ISO which about 6.4GB in size however I could not write that ISO file onto a DVD using k3b tool as it is showing Blank dvd doesn't have enough space. I want to dual boot my computer one with Ubuntu and another one with Centos, For installing CENTOS i need to write that everything ISO on to the DVD which is of 4.7 GB in capacity and then go for installation.

How should i ?

It's just a matter of media.

If the DVD ISO you have to write onto the media is bigger than 4.7 GB, you can use double-layer DVD if your writer is able to support this kind of DVD.

Then you can put almost the double of 4.7 GB on a single double-layer DVD. Of course, if the ISO size exceeds the size limit of a double-layer DVD, you cannot do anything more with a DVD.

There are two links to download CentOS 7 (the latest version) from the download site at centos.org. If you choose the first link by clicking the button that says DVD ISO you be asked to select a mirror and then download a 3.9GB CentOS ISO file that will fit nicely on a DVD. Clicking the other download button will download a bigger ISO that has a lot of additional packages that you don't need.

Alternatively CentOS can also be written to an 8GB USB flash drive (or larger than 8GB) using UNetbootin from the default Ubuntu repositories. For general instructions about how to create a bootable USB stick using UNetbootin see this answer.

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UNetbootin has been dropped from the Ubuntu 18.04 repositories. When I tested the built-in Startup Disk Creator application as a UNetbootin replacement app with 3 non-*buntu live .iso images it worked in Ubuntu 18.04.

  • My friend told me that we could split the ISO into two and then write them on two DVDs but he doesn't know how exactly that could be done. – kaspa Aug 6 '14 at 5:17
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    @kaspa In theory, ISO images can be re-mastered. However, why not apply some common sense. A single ISO image represents a single media. You can expect the installer to expect a single media, then. You would need a fancy smart intermediate diskjockey layer of software (which does not exist) to hide the fact that you split a single disc into two from the installer. Does this sound plausible to you? – Run CMD Aug 6 '14 at 5:26
  • My 8GB pendrive was already made as Bootable pendrive for Ubuntu. However I have a memory card in my phone can i use that to turn it as a bootable flash for booting CentOS. Why because I borrowed my friends connection to download the file and thus consumed 7GB. Because I already got that bigger one I could optimize that. – kaspa Aug 6 '14 at 5:32
  • @kaspa Booting an ISO from a memory card is as slow as molasses in January, and a new 8GB USB flash drive only costs about $5.00 USD now. – karel Aug 6 '14 at 5:51

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