1

I am creating a custom live CD based on Ubuntu 15.10. When the user sees the first boot screen (and doesn't press a key), it will automatically boot into a GUI menu where the user can choose 'Try Ubuntu' or 'Install Ubuntu':

first boot screen image

However, if the user presses a key, it gets a text menu. Selecting 'Try Ubuntu' boots directly into the desired live CD:

text boot menu image

I can successfully remove the installer boot entries in the text menu (isolinux/txt.cfg), but this doesn't change the default boot option when the user does not press any key. Removing the installation package ubiquity is not an option, I just want to prevent the user from starting the installer directly.

How can I change the default boot option to boot into 'Try Ubuntu'?

  • This older post had asked for Live USB but the top answer has covered Live CD with rebuilding the ISO image. For essential instructions only, I have posted an answer below. – clearkimura Jun 12 '16 at 6:04
3

This is the simplified and revised version of my older answer.

To boot directly to Live session, look for /isolinux/isolinux.cfg in the content of the ISO image file and modify these two lines of code:

  1. Replace the default vesamenu.c32 with default live

  2. Comment the last line ui gfxboot bootlogo by inserting # at the beginning of line

Step 2 is required, otherwise the initial splash screen will still be visible until timeout. This is due to ui module will override the default setting, as explained on the Wiki (see References).

Default configuration

# D-I config version 2.0
include menu.cfg
default vesamenu.c32
prompt 0
timeout 50
ui gfxboot bootlogo

Modified configuration

# D-I config version 2.0
include menu.cfg
default live
prompt 0
timeout 50
#ui gfxboot bootlogo

I have tested the modified configuration using Xubuntu 14.04 ISO image. The same steps are likely applicable to any Ubuntu and official flavours, regardless of the release.

References

  1. How do I configure syslinux to boot immediately on Unix & Linux Stack Exchange

  2. Config on Syslinux Wiki

  • Depending on whether you are using the regular desktop or alternate/server ISO and whether your computer is new enough to have UEFI and running in "Legacy" (CSR aka BIOS compatibility) or in UEFI mode you may also need to edit the $ISO_PATH/boot/grub/grub.cfg if to add set default=0 or whatever entry you want it to boot. – dragon788 Jul 19 '18 at 18:55

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