From mboxrd@z Thu Jan 1 00:00:00 1970 From: "pelzflorian (Florian Pelz)" Subject: Re: ISO installer image: GPT versus MBR partitions Date: Tue, 23 Apr 2019 21:50:30 +0200 Message-ID: <20190423195030.czrsu4eut5a37xsx@pelzflorian.localdomain> References: <22381672198740946174@scdbackup.webframe.org> <15876672824612508901@scdbackup.webframe.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from eggs.gnu.org ([209.51.188.92]:36365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hJ1RF-0006wv-Q1 for guix-devel@gnu.org; Tue, 23 Apr 2019 15:50:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hJ1RD-00054E-P4 for guix-devel@gnu.org; Tue, 23 Apr 2019 15:50:45 -0400 Content-Disposition: inline In-Reply-To: <15876672824612508901@scdbackup.webframe.org> List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org Sender: "Guix-devel" To: Thomas Schmitt Cc: bug-xorriso@gnu.org, guix-devel@gnu.org This sounds nice and clean. Thank you! On Tue, Apr 23, 2019 at 08:14:48PM +0200, Thomas Schmitt wrote: > A disadvantage is that for best overall properties, this layout should > have the ISO partition start at 512-byte block 64. This needs a second > superblock and directory tree. About 17 MiB with Guix 0.16.0. > The ISO files are offered on alpha.gnu.org only with xz compression. I suppose most of the 17 MiB would disappear with compression. > So programs like /sbin/isosize can tell the image size even when the > ISO has already been copied to USB stick. > Sounds like this could be used to get a checksum or maybe GPG verification of a USB drive that supposedly contains the iso. > Somewhat off topic: > > The script also has a killer for the MBR signature in the EFI image > file. It gets activated together with partition table erasure by > export MKRESCUE_SED_IN_EFI_NO_PT=extra > It is meant for those users who are curious whether block 0 of an EFI > partition really must look like an MBR to be accepted by EFI firmware. > > It would be interesting to learn about EFIs which fail without MBR > signature. > > The specs say that there may be "compatibility code" in a EFI System > Partition. They talk of "MBR" and understanding partitions in the EFI > partition. I understand it as "may be there, but does not have to". > > Minimal test outside of Guix ISO production: > > - Install GRUB and configure it for EFI for 32 or 64 bit as your firmware > needs. (Both is combinable, as Debian GRUB packages demonstrate.) > > - Create a minimal bootable ISO. It will not offer more than a GRUB > command prompt after it was successfully booted: > > mkdir minimal > touch minimal/empty-file.txt > > export MKRESCUE_SED_MODE=original > export MKRESCUE_SED_IN_EFI_NO_PT=extra > > grub-mkrescue -o output.iso minimal \ > --xorriso=./grub-mkrescue-sed.sh > This prints florian@florianmacbook ~ [env]$ grub-mkrescue -o output.iso minimal --xorriso=./grub-mkrescue-sed.sh grub-mkrescue: warning: Your xorriso doesn't support `--grub2-boot-info'. Some features are disabled. Please use xorriso 1.2.9 or later.. and yields no output.iso for me. Note that xorriso actually has version 1.5.0. Regards, Florian