Help with grub script to run iso

sofasurfer · 09-26-2022, 04:35 PM

I haven't worked on my "booting hard drive iso from grub" project in a while.
I still have not accomplished the task. Before I continue I need to get a couple questions answered. I have been using the following web site...

Code:

https://help.ubuntu.com/community/Grub2/ISOBoot

1) Does the iso need to be mounted in order for this to work? The wiki says it needs to. I am storing the iso in /Downloads. If I mount the /Downloads/xxxxx.iso by using right-click mounting tool the iso is mounted to /media/user/Downloads/xxxxx.iso.

2) Do I or do I not need to run $ sudo update-grub? The wiki says I do. The people on the forum say I SHOULD NOT. Since the grub menu takes its orders from /boot/grub/grub.cfg it seems that update-grub would be absolutely nessessary.

I suspect that part of my problem is that I am using a wrong path in linux loop line of script. I will work on that after I get a full unerstanding of the two questions above.

Sorry for turning this thread into a book. I looks like this is very easy for you guys and so I am thinking I am missing something very simple.

yancek · 09-27-2022, 06:02 AM

Quote:

Does the iso need to be mounted in order for this to work?

No, the link you posted does not tell you to have the iso mounted. The reason given on the page you linked to is to loop mount the iso so you get the correct path for the kernel and initrd files and the exact correct name for each. Sometimes the kernel will include the version number, sometimes the initrd will have an extension. initrd.gz, initrd.lz. These file names need to be exactly correct as does the path.

Quote:

Do I or do I not need to run $ sudo update-grub?

In your case, since you are putting the menuentry in /etc/grub.d/40_custom you do need to update grub. I generally put the entries in the /boot/grub/grub.cfg file and it will show without running update-grub and will show in the grub menu until update-grub is run. If you had the iso entry in grub.cfg and updated grub, it will no longer show in the grub menu.

In the entry you posted above, remove "/dev/sda5" from the loopback loop line.
On the linux (loop) line change "isofrom=/dev/sda5/by-uuid" to "isofrom=/dev/disk/by-uuid" (without quotes) and the correct UUID.

You also have incorrect vmlinuz and initrd.img file names. Not sure where you got that from? I'll post my menuentry below for the same Debian version which does boot so make sure to make the changes above, get the correct drive/partition (he0,5) and the correct UUID for that partition as well as the vmlinuz and initrd files.

Quote:

menuentry "Debian 11.4" {
loopback loop (hd0,gpt3)/debian-live-11.4.0-amd64-cinnamon.iso
linux (loop)/live/vmlinuz-5.10.0-16-amd64 isofrom=/dev/disk/by-uuid/45f8d0f7-05c4-4012-89c1-e088f0852071/debian-live-11.4.0-amd64-cinnamon.iso boot=live components quiet splash --
initrd (loop)/live/initrd.img-5.10.0-16-amd64
}

sofasurfer · 09-27-2022, 07:01 PM

I have learned that the proper grub drive syntax is (hdx,y). Now with this grub menu project I am seeing that the syntax is (hdx,gpty). Why is it different?

colorpurple21859 · 09-27-2022, 07:58 PM

It will work either way the majority of the time. https://www.gnu.org/software/grub/ma...ce-syntax.html

sofasurfer · 09-27-2022, 08:09 PM

I just learned that GPT ab MBR are the partitioning schemes. I have MBR not GPT. As you stated it should work either way (unles you say different). So I will go study now. Be back when I'm done.
Thanks.

colorpurple21859 · 09-27-2022, 09:15 PM

Quote:

I have MBR not GPT.

(hd0,5) will work on both gpt and msdos drives,(hd0,msdos5) will work on a mbr disk not gpt, (hd0,gpt5) will work on gpt disk, not msdos type disk.

sofasurfer · 09-29-2022, 11:39 PM

SUCCESS! I got it working. I think my problems were...
1) I needed to use (hd0,5) instead of (hd0,gpt5).
2) Wrong path. The script I was using was meant to the iso being stored in root (/) but I was storing in /Downloads.
3) I was using the wrong initrd and vmlinux filenames.

Here is my script...

Code:

 #!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
#
menuentry "Debian 11.5" {
loopback loop (hd0,5)/debian-live-11.5.0-amd64-cinnamon.iso
linux (loop)/live/vmlinuz-5.10.0-18-amd64 isofrom=/dev/disk/by-uuid/eb1498be-3ba8-473a-a597-8f9f34d0ba48/debian-live-11.5.0-amd64-cinnamon.iso boot=live components quiet splash --
initrd (loop)/live/initrd.img-5.10.0-18-amd64
}

Which line do I edit to use my iso in a different directory. I tried editing loopback

Code:

loopback loop (hd0,5)/Downloads/debian-live-11.5.0-amd64-cinnamon.iso

and linux(loop)

Code:

linux (loop)/live/vmlinuz-5.10.0-18-amd64 isofrom=/dev/disk/by-uuid/eb1498be-3ba8-473a-a597-8f9f34d0ba48/Downloads/debian-live-11.5.0-amd64-cinnamon.iso

and each way I got "no such file" error.

colorpurple21859 · 09-30-2022, 12:47 PM

If the iso is in your download folder and you don't have a separate home partition it will be similar to this:

Code:

loopback loop (hd0,5)/home/<user name>/Downloads/debian-live-11.5.0-amd64-cinnamon.iso

if it is a separate parition remove the /home

sofasurfer · 10-03-2022, 11:16 PM

I'm doing fine, now, with booting iso from grub. However, I find that when trying to use the Ubuntu 22.04 iso the vmlinuz and initrd exist ONLY as vmlinuz and initrd. They do not have a version number (ie vmlinuz xx.xx.x). This does not work in the grub loader. How is this problem solved.

computersavvy · 10-04-2022, 12:10 PM

Quote:

Originally Posted by sofasurfer

I'm doing fine, now, with booting iso from grub. However, I find that when trying to use the Ubuntu 22.04 iso the vmlinuz and initrd exist ONLY as vmlinuz and initrd. They do not have a version number (ie vmlinuz xx.xx.x). This does not work in the grub loader. How is this problem solved.

This does not make sense. "Doing fine now" and "This does not work" are contradictory terms.

The installation ISO has only one kernel version thus only a single vmlinuz and initrd, both of which work perfectly fine for booting that iso. The grub menu entry needs the exact file name in that ISO and thus does not need anything except what you see.