[SOLVED] Bootable USB "failed to load ldlinux.c32"

[ribault]

I am trying to install Debian on two x86_64 computers, one laptop and one desktop. I created a bootable USB using 'dd' from the file debian-10.5.0-amd64-netinst.iso . This USB looks perfectly bootable according to qemu. However, when trying to boot either computer from this USB, the process immediately gets stuck with the error message

ISOLINUX 6.04 EDD 20190226 EHDD Copyright (C) 1994-2015 H. Peter Anvin et al

Failed to load ldlinux.c32
Boot failed: press a key to retry...

How can I get an error message that refers to 32-bit architecture when the computer and the .iso file are both 64-bit?

[Head_on_a_Stick]

What was the exact dd(1) command that you used? Did you ensure to flush the copy buffers before removing the stick? Can you eliminate a hardware problem with the USB stick or a potentially corrupted ISO image?

[ribault]

The command was adapted from

sudo dd bs=4M if=Downloads/ubuntu-19.04-desktop-amd64.iso of=/dev/sdb conv=fdatasync

which came from https://www.howtogeek.com/414574/how-to ... -in-linux/

I do not know whether this "flushes the copy buffers".

[cuckooflew]

The command was adapted from

sudo dd bs=4M if=Downloads/ubuntu-19.04-desktop-amd64.iso of=/dev/sdb conv=fdatasync

which came from https://www.howtogeek.com/414574/how-to ... -in-linux/

I do not know whether this "flushes the copy buffers".

You need to show us the command exactly how you wrote it, not a copy/paste from some random website, that command is for Ubuntu, not Debian , yes I see you say "adapted", but that could be anything,...are you sure you didn't down load a Ubuntu image, ?
I was just reading earlier today about some others with a similar problem, apparently there are some corrupted images floating around, but since it was for Ubuntu, I did not pay any attention, and did not save the links.
Also,

I do not know whether this "flushes the copy buffers".

"this" ?, it all depends on how you actually worded/wrote the command, and we do not know that either.
You really should read the 'dd' manual, before using the command you could very easily trash you HD just copy/pasting from some random website,

Using dd, on the other hand, can make perfect byte-for-byte images of, well, just about anything digital. But before you start flinging partitions from one end of the earth to the other, I should mention that there's some truth to that old Unix admin joke: "dd stands for disk destroyer." If you type even one wrong character in a dd command, you can instantly and permanently wipe out an entire drive of valuable data. And yes, spelling counts.

"instantly" is a bit of a exaggeration, the 'dd' command is slow, again depending on how it was written, but it can make it almost impossible to access any data, in just a few seconds, or less.
Check and make sure you really downloaded the Debian 64 bit ISO, as well, maybe you got a 32 bit ISO.
I think I would just wipe the usb stick, and try again, if I was not sure about the image, I would download another, and be more careful about which image I selected.The netinstall
images are small enough to be reasonable, and don't take long to download at all.
I have never used a 'dd' command that was even close to what you show. You might try using the example in the manual , it is easier to adapt and works well.

[Head_on_a_Stick]

I do not know whether this "flushes the copy buffers".

Read dd(1) and check what the conv=fdatasync option does

And in future please *never* run a command without understanding exactly what it does — there are *many* bullshit-filled fancy-looking blogs and "guides" on the interweb that offer terrifically bad advice.

The official Debian documentation recommends a much simpler procedure:

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# cp debian.iso /dev/sdX ; sync

It is functionally equivalent to the dd(1) command but much simpler to understand and much easier to remember.

[ribault]

Thank you for these suggestions and explanations. The exact command I had used was

sudo dd bs=4M if=Downloads/debian-10.5.0-amd64-netinst.iso of=/dev/sdc conv=fdatasync

Now I have rewritten the bootable USB from the very same .iso file, using however the program "Startup disk creator" instead of 'dd'. This has solved the issue. (And this shows that the problem was probably an incorrect use of 'dd'.)

[cuckooflew]

Ok thanks, I generally use "&& sync" instead of this :

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conv=fdatasync 

Any way, good that you solved it.
The other thing, I try to avoid using paths, especially long ones, it seems to me like that increases the risk of error , ...but that might just be me.

[LE_746F6D617A7A69]

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oflag=<direct,>sync

This works for dd. Plain 'sync' is an acceptable option for desktop, but not necessarily for servers (or other special use cases) - as it causes a flush of *all* the write buffers by default.
In any case, it's best to watch the LED blinking on the stick - if it has such a "feature" (rare today, because SMD LED increases the device cost by 0.01$ - that can delay buying of a new yacht for the company CEO for 1 week - definitely not acceptable ..