On 26/04/2021 09:27, Alan B wrote:
> On 26 Apr 2021 at 09:18:51 BST, "Chris" <ithinkiam@gmail.com> wrote:
>
>> I thought I sent this last week. Stuck in my outbox.
>>
>> On 23/04/2021 08:21, Alan B wrote:
>>> On 22 Apr 2021 at 23:49:24 BST, "Chris" <ithinkiam@gmail.com> wrote:
>>>
>>>> Alan B <alanrichardbarker@nospamgmail.com.here> wrote:
>>>>>
>>>>> It’s an unrecognised file system as far macOS is concerned but it should
>>>>> still boot if you restart holding down the alt key and allow you to
>>>>> install
>>>>> kubuntu to another USB drive or whatever.
>>>>
>>>> Wait, that message is normal? Most confusing!
>>>>
>>>> That can't be right. If I take the stick that's been burned on windows I
>>>> can see the files just fine on the mac. What's the difference?
>>>
>>> This morning I downloaded kubuntu-21.04-desktop-amd64.iso (the latest
>>> official
>>> version), inserted a spare 32GB USB stick, unmounted the it via diskutil and
>>> wrote the iso to the stick. Note that I did not bother with the hdiutil
>>> conversion.
>>>
>>> sudo dd if=kubuntu-21.04-desktop-amd64.iso of=/dev/rdisk2 bs=4m
>>>
>>> After a few minutes the following message appeared:
>>>
>>> 701+1 records in
>>> 701+1 records out
>>> 2941128704 bytes transferred in 172.057264 secs (17093894 bytes/sec)
>>>
>>> But NO disk unreadable message!
>>
>> Just tried it with kubuntu 21.04 and got the exact same as you including
>> no message.
>>
>>> Diskutil list revealed:
>>>
>>> /dev/disk2 (external, physical):
>>> #: TYPE NAME SIZE IDENTIFIER
>>> 0: GUID_partition_scheme *32.0 GB disk2
>>> 1: Microsoft Basic Data ⁨⁩ 2.9 GB
>>> disk2s1
>>> 2: EFI ⁨ESP⁩ 5.1 MB
>>> disk2s2
>>> 3: Microsoft Basic Data ⁨⁩ 307.2 KB
>>> disk2s3
>>
>> diskutil for k21.04:
>> /dev/disk2 (external, physical):
>> #: TYPE NAME SIZE IDENTIFIER
>> 0: GUID_partition_scheme *30.8 GB disk2
>> 1: Microsoft Basic Data 2.9 GB disk2s1
>> 2: EFI ESP 5.1 MB disk2s2
>> 3: Microsoft Basic Data 307.2 KB disk2s3
>>
>> Repeated it with kubuntu 20.04 and still got the unreadable message.
>>
>> diskutil for k20.04:
>> /dev/disk2 (external, physical):
>> #: TYPE NAME SIZE IDENTIFIER
>> 0: Apple_partition_scheme *30.8 GB disk2
>> 1: Apple_partition_map 4.1 KB disk2s1
>> 2: Apple_HFS 4.1 MB disk2s2
>>
>> So definitely something weird going on, despite it being bootable and
>> seemingly working as expected.
>>
>>> The stick is bootable via restart + alt key. I wonder if the iso format has
>>> changed between kubuntu 20.04 and 21.04?
>>
>> I thought they were always just iso9660. Google doesn't find anything
>> different.
>
> Sorry I meant the actual contents of the .iso file might have been changed to
> make it more macOS compatible, e.g. Partition #2 EFI ESP's format and
> contents?

Checking with Windows - as it's the only thing that can see both sticks
- I see that the kubuntu 21 ISO simply has an 'efi' directory with a few
..efi files within it. The kubuntu 20 is the more usual linux folder and
file structure 'isolinux', 'grub', etc. It's odd - to me at least - that
the more usual one is the one that causes the error on the mac.

Anyway, I see that's not actually an error and I'll be aware of this in
future.

Thanks all!

Chris <ithinkiam@gmail.com> wrote:

[snip]

> Checking with Windows - as it's the only thing that can see both sticks
> - I see that the kubuntu 21 ISO simply has an 'efi' directory with a few
> .efi files within it. The kubuntu 20 is the more usual linux folder and
> file structure 'isolinux', 'grub', etc. It's odd - to me at least - that
> the more usual one is the one that causes the error on the mac.
>
> Anyway, I see that's not actually an error and I'll be aware of this in
> future.

Incidentally having downloaded the kubuntu 21.04 iso and made an installer,
I’ve now created a Linux system which runs on a USB stick plugged into my
MBA. It makes a nice diversion from macOS!

I hope you’ve had success too with your installation.

--
Cheers, Alan

Chris <ithinkiam@gmail.com> wrote:
> On 26/04/2021 09:27, Alan B wrote:
> > On 26 Apr 2021 at 09:18:51 BST, "Chris" <ithinkiam@gmail.com> wrote:
> >> I thought they were always just iso9660. Google doesn't find anything
> >> different.
> >
> > Sorry I meant the actual contents of the .iso file might have been changed to
> > make it more macOS compatible, e.g. Partition #2 EFI ESP's format and
> > contents?
>
> Checking with Windows - as it's the only thing that can see both sticks
> - I see that the kubuntu 21 ISO simply has an 'efi' directory with a few
> .efi files within it. The kubuntu 20 is the more usual linux folder and
> file structure 'isolinux', 'grub', etc. It's odd - to me at least - that
> the more usual one is the one that causes the error on the mac.

USB sticks aren't ISO9660. What you have is a cunningly-constructed image
that can be booted three ways:

ISO9660 with an El Torito partition suitable for booting from a CD/DVD

MBR format with a boot block suitable for booting on an older PC in BIOS
mode, or a newer PC with CSM (legacy BIOS) enabled

With an EFI partition suitable for booting on newer PCs in UEFI mode (like
Intel Macs)

In past times (eg Windows installers) you had to run a 'USB disc creator'
tool to convert an ISO with El Torito into a bootable USB image, which is
avoided by this careful construction. All this cunningness can trip up the
Mac, as you observed, as it can't read the parts intended for other booting
methods.

Theo