Ubuntu: Is there documentation for iso-scan/filename?



Question:

I do not see any documentation for the boot parameter iso-scan/filename=. I see the parameter is handled by the script at location scripts/casper-premount/20iso_scan in Ubuntu's initrd. Here is the script.

What is the closest thing to documentation that exists for this boot parameter?

Also is there any comprehensive list of the boot parameters which are available in Ubuntu?


Solution:1

The french wikipedia article on casper says this (translated into English)

The main phases starting...

If requested by iso-scan / filename = / xxx, looking for an .iso image of CD whose name is / xxx

And the shell script code verifies that this is how it works.

As for a comprehensive list of boot parameters, there isn't likely to be one for such a broad question. That's like asking if there is a comprehensive list of documentation for shell scripts. Those parameters go to the thing that gets control of boot, and as far as I know anyone can write such a thing.


Solution:2

The correct source for that script is from lupin-casper package in Ubuntu

Description: Add support for loop-mount installations to casper The Wubi installer provides a means for installing Ubuntu into a loop-mounted filesystem image hosted on a Windows filesystem. lupin-casper provides hooks to find an ISO image on a hard disk and to read a preseed file from a hard disk, which are used in the early part of this process.

An initramfs hook installs /scripts/casper-premount/20iso_scan inside the initramfs / initrd. If you make a custom live-build Ubuntu based ISO, you need to include that package to have Grub2 be able to live boot.

find_iso parameter was renamed to iso-scan/filename= which sets LIVEMEDIA which is queried in find_livefs in /scripts/casper

Without iso_scan script, you end up stuck in initramfs console with error message: unable to find a medium containing a live file system

Example grub configuration:

menuentry "Ubuntu Live CD" {      set isofile="/efi/boot/ubuntu.iso"      loopback loop (hd0,msdos1)$isofile      linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile noprompt noeject debug      initrd (loop)/casper/initrd.lz  }  

Hope that helps someone... finding the source of iso_scan was rather difficult.


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