Booting iso from Grub

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#1 Sat, 2017-06-10 21:30
  • mrgreen's picture
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Trying to boot alpine-standard iso from grub, my menuentry does not seem to work, wonder if someone can see the issue?

menuentry '[loopback]Alpine x86_64' {
    set isofile='/boot/iso/alpine-standard-3.6.1-x86_64.iso'
    loopback loop $isofile
    set root=loop
    linux /boot/vmlinuz-hardened  alpine_dev=usbdisk:vfat loop=/boot/modloop-hardened modules=loop,squashfs,sd-mod,usb-storage,ext3 quiet
    initrd /boot/initramfs-hardened

Tue, 2018-01-02 17:28
  • Beeblebrox's picture
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I have a similar problem. Booting via loopback does not work , so I tried by extracting the ISO to a folder. Alpine still fails at mount-root stage & drops to busybox

insmod squash4
insmod loopback
set root=(hd0,msdos3)
set path='/downloads/alpn'
linux $path/boot/vmlinuz-hardened loop squashfs sd-mod usb-storage nomodeset
initrd $path/boot/initramfs-hardened

Wed, 2018-01-03 09:02 (Reply to #2)
  • ReproducibleBuildsAreAGoodStandard's picture
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Would any of the following help?
- Wiki section called: Installing GRUB
- Installing bootloader manually
- How do I chain boot from grub to syslinux? - a webpage mentioned in the Alpine wiki.
Could anyone have kindly suggest better guidance, if suitable?

Sun, 2018-01-14 17:07
  • Beeblebrox's picture
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Hi, thanks for the input but:

1. Question assumes that Grub is already installed on HDD - otherwise what's the point of a loopback specific Grub question? As example, I have Grub installed on partitioned USB flash drives, allowing me to boot any ISO or rescue/diagnostic bootable I place on the USB. It's also already present on the PC.

2. Syslinux -> Grub chainload should not be required as the Syslinux syntax is whollely transferable to Grub in most cases.

3. The problem could be with the ISO its self, where kernel needs to pivot to root FS through a linux (not Grub's) loop root mount process; and this might be missing trough deliberate ISO creation parameters.

FYI, for more convoluted boots, memdisk is callable as first entry with:
linux16 /$path/memdisk
Which can provide a memory-based root FS for mounting. This approach also fails with Alpine.

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