Hi,
My 15 year old son has found an old 2011 iMac in the side of the road.
Long story short is that the processor probably works, but we think the
GPU is dead as we cannot get video out of the mini display port
connector, or the screen.
So, I would like to boot from a Debian live ISO with the following
kernel parameters (set in grub.cfg).
ÿ ÿ console=ttyUSB0,19200n8
Now, I can mount up the ISO in loop mode, and get into grub.cfg, but how
do I write this back to the ISO so that I can put in on a USB flash drive?
Thanks!
Paul.
Le 31/05/2026 ?ÿ 17:46, Paul Duncan a ??crit?ÿ:
Hi,
My 15 year old son has found an old 2011 iMac in the side of the road. Long story short is that the processor probably works, but we think the GPU is dead as we cannot get video out of the mini display port
connector, or the screen.
So, I would like to boot from a Debian live ISO with the following
kernel parameters (set in grub.cfg).
?ÿ ?ÿ console=ttyUSB0,19200n8
Now, I can mount up the ISO in loop mode, and get into grub.cfg, but how do I write this back to the ISO so that I can put in on a USB flash drive?
Thanks!
Paul.
Hello,
I don't think you need to do that: https://www.debian.org/releases/stable/amd64/ch05s01.en.html
Chapter 5.1.5. The Boot Screen
"[...]If you wish or need to add any boot parameters for either the installer or the kernel, press Tab (BIOS boot), or e then down arrow
three times then end, to edit the ƒ??linuxƒ?? line of the boot entry (UEFI boot). This will bring the boot command for the selected menu entry and allow you to edit it to suit your needs. Note that the keyboard layout
at this point is still QWERTY. The help screens (see below) list some
common possible options. Press Enter (BIOS boot) or F10 (UEFI boot) to
boot the installer with your options; pressing Esc will return you to
the boot menu and undo any changes you made.[...]
(you can use an Debian install media but I suppose a Debian live media
would propose the same way of entering parameters)
Hi,
Paul Duncan wrote:
So, I would like to boot from a Debian live ISO with the following kernel parameters (set in grub.cfg).
console=ttyUSB0,19200n8
Now, I can mount up the ISO in loop mode, and get into grub.cfg, but howdo
I write this back to the ISO so that I can put in on a USB flash drive?
After having copied /boot/grub/grub.cfg from the ISO to ./grub.cfg and
having edited it, you could create a new ISO from the original one:
orig_iso=debian-live-13.1.0-amd64-standard.iso
new_iso=test.iso
xorriso -indev "$orig_iso" -outdev "$new_iso" \
-map ./grub.cfg /boot/grub/grub.cfg \
-boot_image any replay \
-compliance no_emul_toc -padding included
See also
https://wiki.debian.org/RepackBootableISO#In_xorriso_load_ISO_tree_and_write_modified_new_ISO
(You are aware that "live-*-standard" offers no graphical desktop ?)
-----------------------------------------------------------------
For the more adventurous:
Looking into /boot/grub/grub.cfg of
debian-live-13.1.0-amd64-standard.iso it should be possible to patch
the changed file into a copy of the Debian Live image.
The following procedure is intended for a not mounted "$iso".
Make a copy of the ISO as playground:
iso=test.iso
cp debian-live-13.1.0-amd64-standard.iso "$iso"
Copy grub.cfg out of the ISO:
xorriso -indev "$iso" -osirrox on -extract /boot/grub/grub.cfg grub.cfg
chmod u+w grub.cfg
Learn the size of grub.cfg
ls -l grub.cfg
(mine says 1709 bytes) and memorize it, because your editing will have
to preserve exactly this size.
Edit the copied file grub.cfg and insert the text pieces as needed.
Remove exactly the same number of characters from the remark lines
in the file in order to keep its size unchanged. Verify by ls -l.
Learn the position of the file's content in the ISO:
xorriso -indev "$iso" -find /boot/grub/grub.cfg -exec report_lba --
which will report on stdout something like
Report layout: xt , Startlba , Blocks , Filesize , ISO image path
File data lba: 0 , 3285 , 1 , 1709 ,
'/boot/grub/grub.cfg'
Important is the number under "Startlba" (here: 3285). Multiply it by
the ISO block size of 2048 to get 6727680.
Now you can compose the dd run for putting your edited grub.cfg content
into the ISO:
dd if=grub.cfg of="$iso" conv=notrunc bs=1 seek=6727680 count=1709
Mount the ISO and look into its /boot/grub/grub.cfg to verify that the
new content is present.
-----------------------------------------------------------------
john doe wrote:
I would start at https://wiki.debian.org/ManipulatingISOs#Remaster_an_Installation_Image
This is about of the same age as the Mac, which would match.
But the shown runs of genisoimage and xorriso deal with the ISOLINUX bootloader for Legacy BIOS, not with the GRUB bootloader for EFI.
Have a nice day :)
Thomas
My 15 year old son has found an old 2011 iMac in the side of the road. Long story short is that the processor probably works, but we think the GPU i
So, I would like to boot from a Debian live ISO with the following kernelparameters (set in grub.cfg).
console=ttyUSB0,19200n8do I write this back to the ISO so that I can put in on a USB flash drive?
Now, I can mount up the ISO in loop mode, and get into grub.cfg, but how
some historical considerations:
Jeffrey Walton wrote:
you will find the folks who keep the old PowerMac's alive at the debian-powerpc mailing list
(<https://lists.debian.org/debian-powerpc/>)
In 2011 the Macs had Intel x86 CPUs. The PowerPC Mac era ended in 2006
https://en.wikipedia.org/wiki/Power_Macintosh
I'm not sure about your technical problems. Usually you need a
blessed Apple partition to boot an old Mac.
HFS/HFS+ blessing applies to files or directories, not to partitions.
But indeed some x86 Macs seemed to need a HFS or HFS+ filesystem
which had to be announced by an Apple Partition Map entry.
One can see such a partition table in Debian amd64 ISOs where it marks
the EFI partition with its FAT filesystem. It stems from Matthew
Garret's work to get a bootable Fedora ISO for EFI and x86 Macs.
https://mjg59.dreamwidth.org/11285.html
But Debian never had a HFS+ filesystem image in its ISOs for which the
APM would make sense.
grub-mkrescue for x86 EFI still creates a HFS+ filesystem and marks it
by an Apple Partition Map entry. But even GRUB's then developer
Vladimir Serbinenko could not tell which x86 Mac generation needed HFS+
for booting, when he submitted the HFS+ code for libisofs/xorriso.
That was in 2012. So i assume that a 2011 Mac boots via EFI, not via
HFS or HFS+.
On Sun, May 31, 2026 at 2:53ƒ??PM Paul Duncan <paul.d@soi-team.org> wrote:
My 15 year old son has found an old 2011 iMac in the side of the road. Long story short is that the processor probably works, but we think the GPU is dead as we cannot get video out of the mini display port connector, or the screen.
So, I would like to boot from a Debian live ISO with the following kernel parameters (set in grub.cfg).
console=ttyUSB0,19200n8
Now, I can mount up the ISO in loop mode, and get into grub.cfg, but how do I write this back to the ISO so that I can put in on a USB flash drive?
I'm not sure about your technical problems. Usually you need a
blessed Apple partition to boot an old Mac. I also seem to recall you
may need to boot to a CD rather than a USB device on some models. I
have a PowerMac G5 that needs to boot like that (CD instead of USB).
But you will find the folks who keep the old PowerMac's alive at the debian-powerpc mailing list
(<https://lists.debian.org/debian-powerpc/>). Many folks on the list
are fanatics, and they can probably answer all your questions (and
more).
Jeff
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