Hi,
When I make DVDs of Centos and any others for that matter, I take the following steps:
1. Find an official torrent if possible. (Centos has torrents for the DVD. Unfortunately no Jigdo so far as I know.)
1.1 Torrents come with checksums and the torrent app I use will check the downloaded file against the checksums. Otherwise find a stable mirror close to where you are for better speed.
1.2 If you cant get a torrent find out if the distro vendors offer any other options. IE: Jigdo, zsync etc. etc. I usually try for one of these before going for a strait FTP download. FTP downloads often fail and are not always recoverable in the event of an interruption. Jigdo is my favourite as each and every package and file is downloaded and verified and then the DVD image (.iso) made up from all the packages. It is basically a self checking system and has proven to be very reliable.
2. Once the file is downloaded do a binary checksum using the official checksums found on the vendors homepage or mirror you downloaded from. Information on how to call sha512sum or any checksum tool to make it do a binary level checksum can be found in the man pages. (sha512sum -b filename.iso) I always go for the largest checksum algorithm provided. IE: SHA512SUM if available otherwise SHA256SUM, SHA1SUM or as a last resort MD5SUM. If this passes proceed to step 3.
3. Burning the DVD. This step is the trickiest part to get right.
3.1. Find **reliable** media. Always choose DVD-R. Go with a named brand. I usually go for spindles of 50 or less. I have found that the 100 unit spindles get a bit heavy on the ones at the bottom and I am unsure of the effect shipping and handling has on them.
3.2. Use the following wodim command:
"/usr/bin/wodim dev=/dev/sr0 driveropts=burnfree fs=14M speed=4 -dao ${ISO_FILENAME}" where /dev/sr0 is your DVD device and ${ISO_FILENAME} is your iso you are trying to burn.
to burn the DVD at the slowest possible speed your DVD burner will go for. Use DISK AT ONCE (dao) to write the whole file in one go. Wodim will close the disk session after burning. I know nothing about using windows tools to burn DVDs as I do this on Linux.
4. Check the media against the official checksum you used in step 2. Here are my steps for doing this. Again this has to be done right. Sometimes you will get different results if you try to simply call sha512sum -b /dev/sr0 where /dev/sr0 is your DVD drive.
4.1. Use the isoinfo tool to retreive the blocksize and blockcount of the DVD you are checking. (/usr/bin/isoinfo -d -i /dev/sr0 where /dev/sr0 is your DVD device.)
4.2. Use dd to read the disk using the correct blocksize and blockcount settings and pipe through the checksum tool.
IE: "/bin/dd if=/dev/sr0 bs=${blocksize} count=${blockcount} conv=notrunc,noerror status=noxfer | sha512sum -b" where ${blocksize} and ${blockcount} are the numbers you retrieved from using isoinfo.
conv=notrunc,noerror come from another post I found once. So far so good... The dd man page explains that notrunc means do not truncate the output file and noerror means continue after read errors. status=noxfer is just to keep the whole thing a little quieter by not displaying transfer statistics. You can play with these settings if you like. They have done me fine for over 400 burns since I started doing this over 2 years ago.
This will produce a checksum you can visually compare with the official checksum you retrieved from the mirrors to confirm if your disk is good. I do not know of a better way, without actually installing the OS, of verifying that the media is good. I have all this scripted so complete all these steps every time I ship a DVD to any customer who orders one.
Best regards David Latham
http://www.thelinuxcdstore.com
Message: 1 Date: Mon, 03 Jan 2011 13:37:17 -0500 From: "Lisandro Grullon" lgrullon@CityTech.Cuny.Edu Subject: Re: [CentOS] Centos 5.5 - Kernel Panic while booting. To: amyagi@gmail.com Cc: centos@centos.org Message-ID: 4D21D10D020000890000F53B@email2.citytech.cuny.edu Content-Type: text/plain; charset="us-ascii"
This was very helpful Akemi...I was loading centos in two other
identical servers today and was having such a hard time loading it from DVD, DVD appears to be crashing, I even re-downloaded the image 3 times from three different mirrors and burn them with different applications (Nero, Roxio, and poweriso), worse case scenario it must be something with the Memorex DVD Media. Anyway, after two hours of trying I decided to do a network install and everything went flawless. Good to have many options, Centos rocks!
Akemi Yagi 12/17/10 8:13 PM >>>
On Fri, Dec 17, 2010 at 5:11 PM, Lisandro Grullon wrote:
Akemi, I went through the different mirrors and was unable to locate the ISO
as it
is stated as deprecated or unsupported, is there any plans to fix this
issue
in 5.6 or rather 6.x release. It appears that the latest build from Centos was built back in may, lots of bugs have emerge since them including this one relating to a kernel panic. Please advise in the location of 5.4, i am willing to try it.
It's here:
Akemi
on 1-5-2011 3:50 AM David Latham spake the following:
Hi,
When I make DVDs of Centos and any others for that matter, I take the following steps:
- Find an official torrent if possible. (Centos has torrents for the DVD.
Unfortunately no Jigdo so far as I know.)
Jigdo is a Debianism... Don't know too many places outside of their community using it. It seems to be a cross between bittorrent and rsync...
Scott Silva wrote, On 01/06/2011 02:20 PM:
on 1-5-2011 3:50 AM David Latham spake the following:
Hi,
When I make DVDs of Centos and any others for that matter, I take the following steps:
- Find an official torrent if possible. (Centos has torrents for the DVD.
Unfortunately no Jigdo so far as I know.)
Jigdo is a Debianism... Don't know too many places outside of their community using it. It seems to be a cross between bittorrent and rsync...
from using it, I would say "bittorrent(assembly and sig checking portions) + rsync" does seem a reasonable description.
It was used, at least for a while, on some Fedora spins and IIRC one or two fedora releases. If you are maintaining a personal/local mirror, jigdo makes regenerating 'official' media very fast. And with fedora if you were mirroring the development repo before release, then jigdo meant you could quickly have the 'official' media almost before a torrent could get it to you especially on a slow link (yes I know we don't do those kind of partial pre-releases in CentOS world).
With CentOS they would be nice for those of us who mirror the whole tree and need media, so we could only download the OS directory effectively one time instead of 3 times (os dir, cd media iso, DVD media iso) and then jigdo to generate the iso's as needed. Oh, and you also don't have fun with broken proxies truncating DVDs that are 4GB like happened with CentOS 5.5. Added bonus... unlike bittorent, no ISPs block or mess with jigdo's traffic.
Granted, I don't know how much of the community would make use of them and they take some cpu+labor time to generate.
-
David Latham -
Scott Silva -
Todd Denniston