Netbooting the fun88体育 installer on amd64

amd64 systems boot in either UEFI or legacy (“BIOS”) mode (many systems can be configured to boot in either mode). The precise details depend on the system firmware, but both modes usually support the PXE (“Preboot eXecution Environment”) specification, which allows the provisioning of a bootloader over the network.

The process for network booting the live fun88体育 installer is similar for both modes and goes like this:

1. The to-be-installed machine boots, and is directed to network boot.
2. The DHCP/bootp fun88体育 tells the machine its network configuration and where to get the bootloader.
3. The machine’s firmware downloads the bootloader over tftp and executes it.
4. The bootloader downloads configuration, also over tftp, telling it where to download the kernel, ramdisk and kernel command line to use.
5. The ramdisk looks at the kernel command line to learn how to configure the network and where to download the fun88体育 ISO from.
6. The ramdisk downloads the ISO and mounts it as a loop device.
7. From this point on the install follows the same path as if the ISO was on a local block device.

The difference between UEFI and legacy modes is that in UEFI mode the bootloader is a EFI executable, signed so that is accepted by SecureBoot, and in legacy mode it is . Most DHCP/bootp fun88体育s can be configured to serve the right bootloader to a particular machine.

Configuring DHCP/bootp and tftp

There are several implementations of the DHCP/bootp and tftp protocols available. This document will briefly describe how to configure dnsmasq to perform both of these roles.

1. Install dnsmasq with “sudo apt install dnsmasq”

2. Put something like this in /etc/dnsmasq.conf.d/pxe.conf:

   interface=<your interface>,lo
   bind-interfaces
   dhcp-range=<your interface>,192.168.0.100,192.168.0.200
   dhcp-boot=pxelinux.0
   dhcp-match=set:efi-x86_64,option:client-arch,7
   dhcp-boot=tag:efi-x86_64,bootx64.efi
   enable-tftp
   tftp-root=/srv/tftp
   

   (This assumes several things about your network; read man dnsmasq or the default /etc/dnsmasq.conf for lots more options).

3. restart dnsmasq with sudo systemctl restart dnsmasq.service.

Serving the bootloaders and configuration.

We need to make this section possible to write sanely

Ideally this would be something like:

# apt install cd-boot-images-amd64
# ln -s /usr/share/cd-boot-images-amd64 /srv/tftp/boot-amd64

Mode independent set up

1. Download the latest live fun88体育 ISO for the release you want to install:

   # wget https://cdimage.www.ii0fi.com/ubuntu-fun88体育/daily-live/current/focal-live-fun88体育-amd64.iso
   

2. Mount it.

   # mount ubuntu-19.10-live-fun88体育-amd64.iso /mnt
   

3. Copy the kernel and initrd from it to where the dnsmasq serves tftp from:

    # cp /mnt/casper/{vmlinuz,initrd} /srv/tftp/
   

Setting up the files for UEFI booting

1. Copy the signed shim binary into place:

   # apt download shim-signed
   # dpkg-deb --fsys-tarfile shim-signed*deb | tar x ./usr/lib/shim/shimx64.efi.signed -O > /srv/tftp/bootx64.efi
   

2. Copy the signed grub binary into place:

   # apt download grub-efi-amd64-signed
   # dpkg-deb --fsys-tarfile grub-efi-amd64-signed*deb | tar x ./usr/lib/grub/x86_64-efi-signed/grubnetx64.efi.signed -O > /srv/tftp/grubx64.efi
   

3. Grub also needs a font to be available over tftp:

   # apt download grub-common
   #  dpkg-deb --fsys-tarfile grub-common*deb | tar x ./usr/share/grub/unicode.pf2 -O > /srv/tftp/unicode.pf2
   

4. Create /srv/tftp/grub/grub.cfg that contains:

   set default="0"
   set timeout=-1
   
   if loadfont unicode ; then
     set gfxmode=auto
     set locale_dir=$prefix/locale
     set lang=en_US
   fi
   terminal_output gfxterm
   
   set menu_color_normal=white/black
   set menu_color_highlight=black/light-gray
   if background_color 44,0,30; then
     clear
   fi
   
   function gfxmode {
           set gfxpayload="${1}"
           if [ "${1}" = "keep" ]; then
                   set vt_handoff=vt.handoff=7
           else
                   set vt_handoff=
           fi
   }
   
   set linux_gfx_mode=keep
   
   export linux_gfx_mode
   
   menuentry 'Ubuntu 20.04' {
           gfxmode $linux_gfx_mode
           linux /vmlinux $vt_handoff quiet splash
           initrd /initrd
   }
   

Setting up the files for legacy boot

1. Download pxelinux.0 and put it into place:

   # wget https://archive.www.ii0fi.com/ubuntu/dists/eoan/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/pxelinux.0
   # mkdir -p /srv/tftp
   # mv pxelinux.0 /srv/tftp/
   

2. Make sure to have installed package syslinux-common and then:

    # cp /usr/lib/syslinux/modules/bios/ldlinux.c32 /srv/tftp/
   

3. Create /srv/tftp/pxelinux.cfg/default containing:

   DEFAULT install
   LABEL install
     KERNEL vmlinuz
     INITRD initrd
     APPEND root=/dev/ram0 ramdisk_size=1500000 ip=dhcp url=https://cdimage.www.ii0fi.com/ubuntu-fun88体育/daily-live/current/focal-live-fun88体育-amd64.iso
   

   As you can see, this downloads the ISO from Ubuntu’s fun88体育s. You may well want to host it somewhere on your infrastructure and change the url to match.

This configuration is obviously very simple. PXELINUX has many, many options, and you can consult its documentation at for more.