Title Instructions for generating a bootable usb stick on mac os x are wrong
Priority bug Status chatting
Superseder Nosy List dwt
Assigned To Topics

Created on 2014-08-07.19:23:26 by dwt, last changed 2014-08-11.14:12:32 by dwt.

msg4835 (view) Author: dwt Date: 2014-08-11.14:12:32
Hi Michael,

Am 11.08.2014 um 09:44 schrieb Michael Prokop <>:
> Michael Prokop <> added the comment:
> Well, Mac OS has UEFI support and by accessing /dev/disk2s1 (which I assume
> matches your Grml ISO) this should work just fine.
> What error message do you get?

Sorry, I may be a bit dense, but I don't get how to apply your instructions. I'll try to comment inline:

  % mkdir /Volumes/GRML

Got it, create the mountpoint

  % sudo mount_cd9660 /dev/disk2s1 /Volumes/GRML

Here's where you lost me, /dev/disk2s1 is anything, but not the grml.iso image that is lying in my ~/Downloads/ folder. How do you propose I get the disk subsystem to recognize that it should be attached as a device on /dev/disk2s1?

  % cp -a /Volumes/GRML/* /Volumes/GRMLFOR64/
  % diskutil unmount /Volumes/GRMLFOR64/
  % sudo umount /Volumes/GRML
  % sudo umount /Volumes/GRML

The rest I get, but haven't tried yet. Just out of curiosity, what is the benefit of this method vs. the method the ubuntu guys propose? Their proposal did work for me to get the USB-Stick to boot.

msg4834 (view) Author: mika Date: 2014-08-11.07:44:41
Well, Mac OS has UEFI support and by accessing /dev/disk2s1 (which I assume
matches your Grml ISO) this should work just fine.

What error message do you get?
msg4833 (view) Author: dwt Date: 2014-08-09.20:06:51
Sorry, I can't follow you.

As far as I understand, I would need to mount the grml.iso as a loopback device, however mount_cd9660 doesn't seem to understand '-o loop'. (Not sure why that is, do Macs not know of this option?)

So sorry, your idea doesn't work for me.

msg4832 (view) Author: mika Date: 2014-08-07.21:18:59
Hm, Mac OS's finder actually might really fail (don't have a Mac available right
now), but I'm pretty sure that this should work just fine though:

  % mkdir /Volumes/GRML
  % sudo mount_cd9660 /dev/disk2s1 /Volumes/GRML
  % cp -a /Volumes/GRML/* /Volumes/GRMLFOR64/
  % diskutil unmount /Volumes/GRMLFOR64/
  % sudo umount /Volumes/GRML
  % sudo umount /Volumes/GRML

Could you please verify whether that works for you?
msg4830 (view) Author: dwt Date: 2014-08-07.19:23:24 explains that the 
iso image can be mounted on a mac, which is not true for the current grml .iso images.

This could be due to the issue talked about here:
in-mac-os-x i.e. the filesystem on the iso image being a hybrid for both cd/usb - which 
unfortunately confuses the macs auto mounter.

Converting the image beforehand with a command like 

    hdiutil convert -format UDRW -o ~/path/to/target.img ~/path/to/grml.iso

worked however, and allowed me to use dd to put it onto the stick and boot from it 


Suggestion: Please note this at
id=usb#building_an_efi_usb_key_on_a_mac - I don't seem to be able to change that wiki 
Date User Action Args
2014-08-11 14:12:32dwtsetmessages: + msg4835
2014-08-11 07:44:41mikasetmessages: + msg4834
2014-08-09 20:06:52dwtsetmessages: + msg4833
2014-08-07 21:18:59mikasetstatus: unread -> chatting
messages: + msg4832
2014-08-07 19:23:26dwtcreate