Linux bootable cd rom

Note: This section was contributed by Rizwan Mohammed Darwe ( rizwan AT clovertechnologies dot com )

This section assumes that you are familiar with the process and workings of writing CDs in linux. Consider this to be a quick reference to include the ability to boot the CD which you will burn. The CD-Writing-HOWTO should give you an in-depth reference.

For the x86 platform, many BIOS’s have begun to support bootable CDs. The patches for mkisofs is based on the standard called «El Torito». Simply put, El Torito is a specification that says how a cdrom should be formatted such that you can directly boot from it.

The «El Torito» spec says that any cdrom drive should work (SCSI or EIDE) as long as the BIOS supports El Torito. So far this has only been tested with EIDE drives because none of the SCSI controllers that has been tested so far appears to support El Torito. The motherboard definately has to support El Torito. How do you if your motherboard supports «El Torito»? Well, the ones that support lets you choose booting from HD, Floppy, Network or CDROM.

The El Torito standard works by making the CD drive appear, through BIOS calls, to be a normal floppy drive. This way you simply put any floppy size image (exactly 1440k for a 1.44 meg floppy) somewhere in the ISO filesystem. In the headers of the ISO fs you place a pointer to this image. The BIOS will then grab this image from the CD and for all purposes it acts as if it were booting from the floppy drive. This allows a working LILO boot disk, for example, to simply be used as is.

Roughly speaking, the first 1.44 (or 2.88 if supported) Mbytes of the CD-ROM contains a floppy-disk image supplied by you. This image is treated like a floppy by the BIOS and booted from. (As a consequence, while booting from this virtual floppy, your original drive A: ( /dev/fd0 ) may not be accessible, but you can try with /dev/fd1 ).

First create a file, say «boot.img», which is an exact image of the bootable floppy-disk which you want to boot via the CD-ROM. This must be an 1.44 MB bootable floppy-disk. The command below will do this

dd if=/dev/fd0 of=boot.img bs=10k count=144

assuming the floppy is in the A: drive.

Place this image somewhere in the hierarchy which will be the source for the iso9660 filesystem. It is a good idea to put all boot related files in their own directory («boot/» under the root of the iso9660 fs, for example).

One caveat — Your boot floppy must load any initial ramdisk via LILO, not the kernel ramdisk driver! This is because once the linux kernel starts up, the BIOS emulation of the CD as a floppy disk is circumvented and will fail. LILO will load the initial ramdisk using BIOS disk calls, so the emulation works as designed.

The El Torito specification requires a «boot catalog» to be created as well. This is a 2048 byte file which is of no interest except it is required. The patchwork done by the author of mkisofs will cause it to automatically create the boot catalog, but you must specify where the boot catalog will go in the iso9660 filesystem. Usually it is a good idea to put it in the same place as the boot image, and a name like boot.catalog seems appropriate.

So we have our boot image in the file boot.img , and we are going to put it in the directory boot/ under the root of the iso9660 filesystem. We will have the boot catalog go in the same directory with the name boot.catalog . The command to create the iso9660 fs in the file bootcd.iso is then:

mkisofs -r -b boot/boot.img -c boot/boot.catalog -o bootcd.iso .

The -b option specifies the boot image to be used (note the path is relative to the root of the iso9660 disk), and the -c option is for the boot catalog file. The -r option will make approptiate file ownerships and modes (see the mkisofs manpage). The «.» in the end says to take the source from the current directory.

Now burn the CD with the usual cdrecord command and it is ready to boot.

The first step is to get hold of the bootable image used by the source CD. But you cannot simply mount the CD under linux and dd the first 1440k to a floppy disk or to a file like boot.img . Instead you simply boot with the source CD-ROM.

When you boot the Win98 CD you are dropped to A: prompt which is the actual ramdisk. And D: or Z: is where all the installables are residing. By using the diskcopy command of dos copy the A: image into the actual floppy drive which is now B: The command below will do this.

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How to Create Bootable Linux CD

Q. I’m using CentOS Linux and I’d like to create bootable Linux CD for the same. How do I create an installation boot disk?

A. You need to find images/ directory located on CentOS / Fedora / RHEL or any other Linux distribution. This directory contains image files that can be used to create media capable of starting the Linux installation process.

More about images

boot.iso – The boot.iso file is an ISO 9660 image of a bootable CD-ROM. It is useful in cases where the CD-ROM installation method is not desired, but the CD-ROM’s boot speed would be an advantage. To use this image file, burn the file onto CD-R (or CD-RW) media as you normally would.
diskboot.img – The diskboot.img file is a VFAT filesystem image that can be written to a USB pendrive or other bootable media larger than a floppy. Note that booting via USB is dependent on your BIOS supporting this. It should be written to the device using dd.

Step # 1: Copy boot.iso to /tmp

Type the following command,
# cp boot.iso /tmp
Unmount cdrom
# cd; eject

Step # 2: Insert blank CD R/RW media

Find device name:
# cdrecord -scanbus
Write /tmp/boot.iso to blank cd, enter:
# cdrecord -v -dao dev=1,0,0 /tmp/boot.iso
Replace 1,0,0 with your actual device name obtained using cdrecord -scanbus command. See how to burn ISO images to Cds and CD-RWs under Linux for more information.

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Write diskboot.img to floppy

This is optional and use the dd command to copy the image to the floppy / usb pen:
# dd if=diskboot.img of=/dev/fd0 bs=1440k

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Create Bootable CD/DVD/USB Based on Windows PE or Linux

How to create bootable disc CD, DVD or USB? AOMEI Backupper can help to create bootable disc of Windows PE, Linux and make ISO bootable file easily and efficiently.

AOMEI Backupper

An easy-to-use and versatile tool offers data backup, files sync, disaster recovery, and disk clone solutions.

Key Features

Create System Image

Backup all contents in system drive to an image, including Windows and apps.

Create Disk Image

Backup entire disk to an image. Support HDD/SSD, MBR/GPT, removable drives.

Backup Files

Backup specified files to local disks, external drives or NAS/network share.

Clone Hard Disk

Clone a hard disk to another or an SSD with larger or smaller capacity.

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Set & forget. Create a schedule to backup data automatically.

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Introduction of Bootable CD

Bootable CD is a kind of special disc, which contains a bootable operating system. This operation system generally is a compact version of Linux or Windows PE. A disc which has been installed a compact operating system is called Bootable CD.

If the Windows operating system installed on hard disk, such as, Windows XP/Vista/7/8/10, can not boot or suffers a system crash, we can restore the operating system through a bootable CD so as to make the operating system on the disc work normally again.

It is always recommended to backup Windows drivers so as to restore them and insure a working computer after recovering system. Or you may download the magic tool Driver Talent for Network Card which is able to download and install network drivers without internet connection in case of no internet after system recovery.

Create bootable disc will help you boot your computer successfully. The bootable CD maker AOMEI Backupper supports creating two kinds of bootable CD or USB Flash Drive. One is Linux boot disc, and another is Windows PE boot disc. The former one can be created straightway, while the latter one may require installing Windows AIK kit in your operating system in advance. Linux boot disc has several drawbacks. For example, some hardware does not support it, such as, hardware RAID; and some functions of the software can not be used. Therefore, we strongly recommend creating Windows PE bootable CD first. The comparison of the available functions between these two types of disc is as follows.

Features	Windows PE bootable CD	Linux bootable CD
File, Folder, Disk and partition backup
System Backup
System Restore
File, Folder, Disk and partition Restore
Disk and partition clone
Explore image file
Support hardware RAID

Making Windows PE Bootable CD

When making a Windows PE bootable CD, the free backup software -В AOMEI Backupper will check out whether your operating system meets the corresponding requirements. For instance, is it necessary to install Windows AIK? If it does, this software will provide corresponding notices. If your operating system is Vista or higher version of OS, such as, Windows 7/8/2008 R2/2011/2012, usually you can directly create a bootable CD without installing Windows AIK.

Here come the steps of how to create bootable disc with AOMEI Backupper.

Step 1.В Under the «Tools» tab, select «Create Bootable Media» option.

Step 2.В In the pop-up window, choose «Windows PE-create bootable disc based on Windows PE» option, and then click «Next».

Step 3. In the pop-up window, select «Burn to CD/DVD» option, and then click «Next». (Notes: you need a CD-burning program, and also you need to insert the CD/DVD into the CD-ROM, or the «Burn to CD/DVD» option will not be available).

Step 4. When the operation is done, just click «Finish» to exit the interface.
Here you have already made a bootable CD. Then, you can reboot your computer, and set the CD-ROM as the first boot device in BIOS settings and test if your computer can boot from the disc. Then, when something bad happens, you can performВ windows 10 system image restore to different computer, even with dissimilar hardware.

Making Bootable USB Flash Drive or USB Disk

If you do not have a CD/DVD, but a USB flash drive, you can use a USB drive to replace CD/DVD, to create a bootable USB drive. The making way is the same as creating a bootable CD. You just need to see the following screenshot, select «USB Boot Device» and click Next.

Making Linux Bootable CD

The way to create Linux bootable CD is just the same as those steps of creating Windows PE bootable CD/USB Drive. The only difference is that you can create this kind of CD at any time without meeting any requirement, or need a Windows AIK installation. Just like what has been said before, the compatibility of Linux bootable CD might be a little bit poorer.
The operating process of making Linux bootable disc is just similar to that of making Windows PE bootable disc. You can just refer to the steps above. Here is is screenshot:

During the process of making Linux CD, if you do not possess a CD, AOMEI Backupper allows you create a bootable USB drive. The only requirement is that, when choosing the bootable media type, select the USB Boot Device. Then you can boot the operating system from the USB disk to do the recovery operations.

Note: Linux bootable media does not support for EFI/UEFI boot, if your computer boot mode is UEFI mode, you need to enter into BOIS to change the BIOS boot mode from UEFI to Legacy Boot Mode like the following snapshot (you may also learn how to change the setting by referring to the manual of your motherboard).

Making Bootable ISO File

If you do not have CD or USB disk, or if there is a problem when making the bootable CD, you could create a bootable ISO file first, and then employ some burning software, like Nero to burn ISO file to a CD or USB disk.
Here come the operating steps of creating bootable ISO file.

First, select «Create Bootable Media» option under the «Utilities» item. Then,В select the «Export ISO file» option, and then click «Next».

At last, click «Finish» when the operation has been done.

Now, after creating the ISO file, you can easily burn ISO to CD or USB with burning tool and follow the tutorial how to burn ISO file to CD/USB to burn this ISO file. Also, you can complete this task with the Windows 7 integrates built-in burning utility by right clicking this ISO file > Open With > Windows Disc Image Burner.

Note: If you don’t want to create bootable disc, you could enable AOMEI Backupper recovery environment in Windows boot options menu, then boot from the recovery environment to backup, restore, clone data.

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