Ubuntu – GRUB menu linux parameters explained


I am trying to boot from an Kubuntu ISO directly from my hard drive. I have found several instructions like here or from this ubuntu guide. Well, everything seems quite clear except from the Linux parameters.

A typical example of a menuentry in /etc/grub.d/40_custom is this:

menuentry "Ubuntu 12.04.2 ISO" {
        set isofile="/home/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # or set isofile="/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # if you use a single partition for your $HOME
        loopback loop (hd0,5)$isofile
        linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile noprompt noeject
        initrd (loop)/casper/initrd.lz

which passes parameters noprompt noeject. I have seen other examples where other combinations are used like quiet splash. I found some explanation about the latter parameters in here but for the former I could not find any. I have found a combination of all in here also where it also mentions toram(?) as parameter.

I know that these are probably Linux kernel parameters and there a lot to be presented here but I couldn't find a definition neither in here. So, could someone explain what the rest of the parameters might do and when to use them or if there are some other typical useful parameters for my case (isoboot that is).

Best Answer

  • Those additional options (toram) are related to casper, which is a ramfs wrapper I believe. http://manpages.ubuntu.com/manpages/focal/man7/casper.7.html

    toram attempts to place the ISO in its entirety into memory. It's almost always better to do this. You can even remove the USB drive after it's booted.

    Other options are kernel parameters and boot parameters, all crammed into those 2 lines.

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