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Ubuntu 16.04 Unattended-Install for UEFI using preseed

Create a Legacy and UEFI automated Ubuntu ISO installer. Using preseed.cfg and post-install scripts, this can completely automate installing Ubuntu 16.04. This may work with other distros, but I have yet to test this. Your personal variables such as default packages, SSH keys and username/password will obviously need to be edited before use.

Follow the steps below to create your own image.

cd /root
wget http://releases.ubuntu.com/16.04.2/ubuntu-16.04.2-server-amd64.iso

Extract ISO

xorriso -osirrox on -indev ubuntu-16.04.2-server-amd64.iso -extract / custom-iso

Edit /boot/grub/grub.cfg

This is for UEFI booting. This specifies the timeout on the grub menu to 1 second, tells grub what network adapter to use and grabs the preseed file.

cd /root/custom-iso
nano boot/grub/grub.cfg

Replace the contents with grub.cfg with the following. Make sure you alter the HTTP location of your preseed file!

if loadfont /boot/grub/font.pf2 ; then
        set gfxmode=auto
        insmod efi_gop
        insmod efi_uga
        insmod gfxterm
        terminal_output gfxterm
fi
set default=0
set timeout=1
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray

menuentry "Install Ubuntu Server" {
        set gfxpayload=keep
        linux /install/vmlinuz gfxpayload=800x600x16,800x600 hostname=ubuntu16-04 --- auto=true url=http://preseed.handsoff.local/ubuntu-16-04/preseed.cfg quiet
        initrd  /install/initrd.gz
}

Edit /isolinux/txt.cfg

If you do not want to enable preseeding on a legacy device, this step isn't necessary.

nano isolinux/txt.cfg

Replace the contents with the following. Make sure you alter the HTTP location of your preseed file!

GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=1

default install
label install
menu label ^Install Ubuntu Server
kernel /install/vmlinuz
append preseed/url=http://preseed.handsoff.local/ubuntu-16-04/preseed.cfg bga=788 netcfg/choose_interface=auto initrd=/install/initrd.gz priority=critical --

Obtain isohdpfx.bin for hybrid ISO

cd ../
sudo dd if=ubuntu-16.04.2-server-amd64.iso bs=512 count=1 of=custom-iso/isolinux/isohdpfx.bin

Create new ISO

cd custom-iso
sudo xorriso -as mkisofs -isohybrid-mbr isolinux/isohdpfx.bin -c isolinux/boot.cat -b isolinux/isolinux.bin -no-emul-boot -boot-load-size 4 -boot-info-table -eltorito-alt-boot -e boot/grub/efi.img -no-emul-boot -isohybrid-gpt-basdat -o ../custom-ubuntu-http.iso .

Confirm partitions

As we have created a hybrid ISO, meaning it can be used in both UEFI and Legacy modes, it's good to make sure EFI is showing in the partition table. You can check this by using the following command:

fdisk -l custom-ubuntu-http.iso

If the partitions have been created correctly, you should see something similar to the following:

Disk custom-ubuntu-http.iso: 841 MiB, 881852416 bytes, 1722368 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x19a15b31

Device                  Boot Start     End Sectors  Size Id Type
custom-ubuntu-http.iso1 *        0 1722367 1722368  841M  0 Empty
custom-ubuntu-http.iso2       4036    8899    4864  2.4M ef EFI (FAT-12/16/32)

Preseed file

Upload preseed .cfg file to location specified in grub.cfg/txt.cfg. As we have specified networking within the Grub menu, we are now able to pull the preseed file over network using DHCP.

User passwords

You can either encrypt your password, or pass it over plain text. If you want to use plain text, then comment the line d-i passwd/user-password-crypted and uncomment the two lines above containing passwd/user-password and passwd/user-password-again. Don't forget to update your password. If you would like to hash the password, enter the following line. This will prompt for a password and return a hash for you to use. You must then add your hash to the preseed.cfg file.

mkpasswd -m sha-512

Post install script

The preseed uses wget to download your post-install.sh file to the /tmp folder just before the machine reboots after installation. My script does the following:

  • apt-get update && upgrade -y
  • apt-get dist-upgrade -y
  • Installs basic packages defined at the head of the script
  • Installs SSH keys for both the default user, and root. You must edit the post-install.sh file to add your keys
  • Edits /etc/sshd_config to allow root ssh access, as well as password authentication
  • Configures networking specified at the top of the script
  • Changes the hostname which is defined at the top of the script.

Unfortunately, there seems to be a bug in Xenial which ignores the hostname set in the preseed file. Therefore, a default hostname is set within grub to remove the prompt during installation. If you know a better way around this, please commit a PR!