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Old 05-12-2011, 12:55 PM   #1
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Unhappy What is MD5?

What is MD5? When I attempt to download an .iso I see thIS in the list next to the linux version I'm interested in downloading. Also, I have downloaded several .iso and am not sure if I'm to burn it to a CD/DVD or install directly to my pc. I have Virtual Close Drive which is suppose to allow me to install the .iso directly, but I haven't tried it yet. So botton line is, do I need to download the MD5 and the version of linux I'm interested in and plus, should I burn them both to a CD/DVD?
Old 05-12-2011, 12:57 PM   #2
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Old 05-12-2011, 01:03 PM   #3
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Hi and welcome to LQ.

MD5 hash is used to check the integrity of the file you've downloaded. It's always good practice to do it. For more information see:

The most common way of installing linux is burning an .iso image on a cd/dvd and starting a computer off the cd/dvd. Normally you won't be able to install an operating system using any virtual drives. There are ways, however, to install Ubuntu from your running windows system. See
Old 05-12-2011, 04:22 PM   #4
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Thanks for you guys reply. I kind of figured it was some type of checking for integrity, but was wondering if I was to download it and then download the linux version I want. Then what...? Would I see some self explanatory way to use it? How do I run it against the version of linux I downloaded?
Old 05-12-2011, 04:47 PM   #5
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I see that this is the command to run:

Uses md5sum, the simple way is run the command line straight away. Let say you want to check the file ubuntu-6.10-desktop-i386.iso.

md5sum ubuntu-6.10-desktop-i386.iso

But does this mean I'm to download MD5 and the version of linus I want? Then run this command?
Old 05-12-2011, 08:12 PM   #6
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What operating system will you be using to download the iso file and perform the check?
Old 05-12-2011, 10:00 PM   #7
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MD5, like SHA1 and SHA2 and a few others, is actually a mathematical algorithm. There are many implementations of it, for every operating system under the rainbow.

The essential purpose of all of these algorithms is ... to detect changes. If you change one single lousy bit in an umpteen-gigabyte file, these algorithms will produce "a radically different number, whatever that number may be." (And, believe it or not, the fact that the number is "radically different" is actually quite important.)

This is why these algorithms are called "digital signature" or "digital fingerprint" (or, not accurately at all, "checksum") algorithms.

The Linux/Unix command md5sum filename will, given a filename, read the contents of the file, calculate the MD5 signature ("checksum") for those contents, and print it out. (Notice that this command implements and uses the MD5 algorithm ... but it isn't, strictly speaking, "the algorithm.")

Last edited by sundialsvcs; 05-12-2011 at 10:03 PM.
Old 05-13-2011, 06:21 PM   #8
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I'll be using window XP I guess. This is why I typically order the CD/DVD with linux on it to avoid all this. But I wanted to see if I just was new to this procedure by asking you guys. So let me be clear, I download both the MD5 and the linux version I want, run the command md5sum <filename> from the command prompt in XP. And I'll get some type of confirmation. At the point I should burn to a CD/DVD and load on the pc I want it on, correct?
Old 05-13-2011, 11:49 PM   #9
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There are some utilities (including free) on Windows also for both interactive and command line work.

In my orgn, we use both types.

As sundialsvcs said, the syntax is "md5sum filename" and the output is near standard. Something like"
Old 05-14-2011, 04:21 AM   #10
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Under windows, you can use e.g. digestit. It installs in the context menu, so right click on a file in windows explorer will give you the option.

How to use:
  1. download a file (e.g. an iso)
  2. copy the associated MD5sum (select the full text xxxxxxxxxxxx)
  3. right click the downloaded file in windows explorer, select 'digestit' -> 'verify MD5' and paste the copied MD5sum in the textbox and click OK
  4. after a while it will tell you if the given MD5sum matches the MD5sum that the program calculated
Old 05-14-2011, 04:32 AM   #11
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This is one reason why I prefer to get .isos via torrents.

MD5 checksumming is all well and good, and works, but its a lot easier to just d/l using a torrent client, then when its d/led use the 'verify data' option. Every decent torrent client I've ever used has that option.


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