Re: Changing boot parameters on Debian standard ISO

At Sun, 31 May 2026 19:03:38 +0200 didier gaumet <[email protected]> wrote:

> 
> Le 31/05/2026 à 17:46, Paul Duncan a écrit :
> > 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).
> > 
> >      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 “linux” 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.[...]
> 

Note: this assumes that the keyboard & basic *graphics* screen works.  If the 
graphics screen in tty mode does not work, you can't do this.

I don't know if an iMac exposes a tty console port or even if the iMac 
motherboard even has a PC-style "bridge" chipset.  (*PC* motherboarda have a 
bridge chip which contains basic I/O interfaces (IDE/SATA, serial, USB, 
floppy, etc.) following standard PC interface logic. I am not sure what 
Apple's x86 systems do exactly.  It might be the same, but I am not sure.  

But yes, it is not really possible to edit and re-write the ISO.  The ISO-9660 
file system is read-only by design.   If you change the GRUB configuration you 
need to re-create the ISO-9660 from scratch -- this is doable, but a 
non-trivial process.


> (you can use an Debian install media but I suppose a Debian live media 
> would propose the same way of entering parameters)

The OP is using a Debian install ISO.

> 
> 
>  
>