Installing Qubes via write-once DVD

Hi I am wanting to buy a newish low energy qubes compatible machine and preferably with Qubes DVD.

Is there such a thing as a write once DVD any more? I understand they can be formatted as USB drives and miraculously become write many devices.

My network has been attacked by Viruses and I am not 100% sure that the viruses have been cleared completely. So I would rather not down load my OS and would rather be able to ensure that the installation material is incorruptible.

Any Advise welcome Thanks, I am in the UK.

I have no comment regarding your machine search, but I can share some of my thoughts on DVDs. I hope it helps.

DVD-R and DVD+R optical disks do still exist and can still be purchased online or in-store, though I believe the ISO size of Qubes OS (5.1 GB / 4.8 GiB) well exceeds the capacity of single-layer DVDs (4.7 GB / 4.38 GiB). Dual-layer DVDs (8.55 GB / 8.15 GiB) would be necessary for a DVD installation, which are harder to come by in stores. In my experience, DVD-R DL are impossible to find in stores and almost just as hard to find online; while DVD+R DL are not usually stocked in places like Wal-Mart, but can sometimes be found in large electronics stores and and always online.

It has been many years since I have used Windows, but I believe both recordable and rewritable disks can be reused “like a USB flash drive”, as Windows describes it, by running the disk as a “Live File System”. That is where much of this confusion probably comes from, and Windows does not help to dispel that. Whereas rewritable disks can be used in this way repeatedly, though, recordable disks cannot be “rewritten” so much as “written further”.

How recordable disks work is that they have a special dye coating them that is physically and irreversibly “burned” onto the disk in the binary pattern of whatever data you burn to it. When used “like a USB flash drive”, you are still burning the data to the disk, but you are not “mastering” it with that data, so any extra space left on the disk can still be used for future burnings. Once all the space is used up, however, there is not much more you can do about it. True to their purpose, they cannot be overwritten with further arbitrary data. (Technically, they can be forcibly overwritten with all 1s, which effectively wipes the disk, but this only works because you would be burning in every single bit rather than a binary pattern of 0s and 1s.)

So, while it is strictly true that recordable disks can be used as “write many devices”, it is only in a limited capacity otherwise consistent with how recordable disks work. To avoid this, you can choose instead to “master” the recordable disk. Make sure it is a DVD±R, though, if you want the benefits of a “write-once” disk. A more paranoid approach might be to force-burn the rest of the disk or otherwise fill it with random data before mastering. I think a Windows program called Nero has a “finalize” feature that more or less does that, though it is often used by people who dislike how “ugly” and “unprofessional” the burn line looks and want to push it to the edge. I have never used Nero and I am not aware of any Linux software with a comparable feature, though simply filling the DVD is sufficient.

If you want to be especially confident that you burn a legitimate copy of Qubes OS, be sure to verify the ISO checksum and PGP signature. It may also be best to do all this on a known safe device, one that has no history with malware or which at least has been successfully restored to a verifiably secure state. Once you have your newly burned DVD±R, you can then proceed to verify the checksum and/or the signature on other independent devices if you want to be extra confident. If they all report the same information, then either they are all lying to you or, more likely, none of them are.

Then, so long as everything checks out, you can proceed to install Qubes OS (or anything else) from a DVD with confidence.

More information about this can be found in the following Qubes documentation:

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I think it may be best to dedicate this thread exclusively to the DVD topic (the main part of your question). So I’ve renamed the title. If you wish to open another one exclusively on “low energy qubes machine”, feel free to do so. Keeping things separate helps other people with the same question easily find the answers :slight_smile:

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Thanks for a more detailed info.

Given that if you write to the end you cannot “Rewrite” the disk what software writes the ISO image and then fills the rest of the free disk space with ones. So that the disk cannot be “rewritten”.

I presume that the USB FORMATING must overwrite the MBR or equivalent in a way that stops the ISO from booting. what are the details of that. Sorry two questions one one reply answer either or both ad you can.

Here is a script that may serve as a starting point for burning DVDs on gnu/linux systems:

# file:
# desc:	create a bootable cd/dvd from an iso (or create one)
# usage: file.iso
## mkisofs \
#  -R -J -A "Debian Install 1" \
#  -hide-rr-moved \
#  -v -d -N \
#  -no-emul-boot -boot-load-size 32 -boot-info-table \
#  -sort sw12p1/isolinux/iso.sort \
#  -b sw12p1/isolinux/isolinux.bin \
#  -c sw12p1/isolinux/isolinux.boot \
#  -V Debian1" . | cdrecord -v dev=/dev/sr0 speed=8 -eject -data - > $0_`date +%Y%m%d_%H%M`.log 2> $0_`date +%Y%m%d_%H%M`.err
# The following line is a hard wired version where the iso already exists:
sudo cdrecord -v dev=/dev/sr0 speed=8 fs=1024k -eject -data debian-live-10.2.0-i386-xfce.iso > cd-dvd_burn_boot_iso_`date +%Y%m%d_%H%M`.log 2> cd-dvd_burn_boot_iso_`date +%Y%m%d_%H%M`.err
# The following did not work with 4.7GB blank DVDs, apparently fs=8m -tao were the problem.
# The err log reported that the disks did not support TAO. Also fs=1024k was sufficient to have
# adequate throughput, and no increase was to be expected with higher sizes.
# cdrecord -v dev=/dev/sr0 speed=8 fs=8m -tao -eject -data linux-live-xfce-current.iso > $0_`date +%Y%m%d_%H%M`.log 2> $0_`date +%Y%m%d_%H%M`.err
## found cdrw with `sudo dmesg | grep hdc`
## found cdrw with 'sudo dmesg | grep -C5 cdrom'

Sorry about the forced highlighting.

Formatted this to make it more readable.

Having the markdown formatting as an option seems more reasonable. But I’ll do my best to adapt. Thanks for your help.

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I want to add that if your PC has Nvidia graphics which cannot bypass it (e.g. in a laptop), you’ll have to modify configs in the iso. Burning that modified iso onto a DVD will not yield a bootable DVD, in my experience, so keep that in mind.

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