How to verify that the ISO I downloaded is bootable before I burn it?

Question

How can I check that the ISO image I've downloaded is bootable, before I burn it?

Solution 1

isoinfo can probably tell you if it has the right files to boot if you want quick and dirty. isoinfo -l -i is_it_bootable.iso will list the directory structure so you can check for files a live cd / bootable cd should have.

isoinfo -d -i is_it_bootable.iso will tell you if the CD has an El Torito section. Ubuntu's live CD iso reports:

Eltorito validation header:
Hid 1
Arch 0 (x86)
ID ''
Key 55 AA
Eltorito defaultboot header:
    Bootid 88 (bootable)
    Boot media 0 (No Emulation Boot)
    Load segment 0
    Sys type 0
    Nsect 4
    Bootoff 8F 143

Solution 2

You check the MD5SUM. See https://help.ubuntu.com/community/HowToMD5SUM.

The iso at http://www.ubuntu.com/desktop/get-ubuntu/download is guaranteed by ubuntu to be bootable, a valid MD5SUM therefore asserts that the iso is bootable.

Solution 3

Performing a cryptographic hash verification of the ISO file you downloaded consists of the following steps.

1. Open a terminal and type the following:

   md5sum 
   

   Note: there's a space after the md5sum.

2. Now open Nautilus and browse to the folder containing the ISO file.

3. Drag the ISO file to the open terminal window. This will insert the path / filename of the ISO file into the terminal window.
4. Press Enter in the terminal window.
5. The first part of the output is the MD5 hash of the CD.
6. Go here and find the directory that corresponds to your release and find the file MD5SUMS. Compare the hash of your ISO file to the appropriate entry in that file.

If the two hashes do not match, then your ISO file is corrupt and you will need to download it again.

Solution 4

If you have a good-enough CPU, install VirtualBOX, and setup some Virtual Machine. Make it point to the ISO as the CDROM, and configure it to first boot from CDROM. It willboot from the ISO file directly, without actually having to burn the file.

Another thing that I always do, as a general practice, is to actually put the ISO on a USB key and boot from it, which is something now possible with most computers. UNETBOOTIN (just google it) will do this for you. Just expect the USB disk to be completely wiped.

I now never boot from a CDROM anymore. I can't remember the last time I actually burned a CDROM.

Solution 5

A superficial way is to run file. In the end of the line it prints whether iso is bootable, e.g.

$ file fd11src.iso
fd11src.iso: ISO 9660 CD-ROM filesystem data 'FD11SRC' (bootable)

A more profound way is to use an emulator like qemu:

qemu-system-x86_64 -boot d -cdrom image.iso -m 512

If it loads, then everything is fine. Despite the complete emulation, to run it is very easy and not resource-consuming.

These methods should work for any Linux distribution.

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Comments

[Byte Commander]

Related: How can I check the integrity of a downloaded Ubuntu CD?

[The Student]

The md5sum tells if the iso is bootable? (I want to know if it's bootable, not if it was correctly downloaded)

[goo]

If the file on the source site was bootable, and md5sum gives the same result on both copies, then there's an insignificant chance that the files differ, and you can assume that your copy is bootable, too.

[guntbert]

This looks a lot like a Windows program.

[U880D]

For me the best approach seems to be to validate the El Torito header.

[Jonathan Cast]

OMG this produces a ton of output! Why would you recommend this?! How could anyone possibly read it?

[Ploni]

@guntbert They just released a Linux version of the program.

[MaXi32]

I don't understand this answer, which output that shows the ISO is valid ? I corrupted my ISO file with 1 byte deletion and it still produce the same Eltorito output. What are we looking for here ?