I successfully created a dual boot configuration on an acer travelmate spin B118 with endless OS preinstalled on the internal SSD and siduction (Debian sid) on a 64GB USB 3 stick.
- Backup contents of the USB stick if you need the contents, it will be overwritten.
- Copy the ISO to the stick either with
cp <iso-file> <device>
or
dd if=<file> of=<device> bs=4M; sync - Boot from the stick (you may have to fiddle a bit in the BIOS) after having added
toramin the boot command line parameters of the selection ISO - HD-USB Stick - Use gdisk to create a new GPT (GUID Partition Table) on the stick
- start the installer (calamares) and choose the whole stick for siduction. This will create an ESP (EFI System Partition), a root partition and a swap partition on the stick.
- In my case the siduction installer was not able to finish the installation (see my post on the siduction forum
- Install rEFInd from the repository
apt install refind, it will update the ESP (EFI System Partition) on the stick with a correct boot manager and find the siduction.
I guess this should work out very similar with Ubuntu, but I am not really sure that current versions of Ubuntu use also Debian’s isohybrid technology (see: https://www.debian.org/CD/faq/#write-usb), which is a necessary precondition for step 1 above. I could not find similar information for Ubuntu quickly.
Edit: On my Acer notebook, I have to hit F12 when the Acer splash screen appears to be able to boot from the stick. On the following menu I find the internal ssd and the stick. I can choose the stick with siduction and it will present me the rEFInd menu, where I also could boot endless. When I choose siduction, I get Siductions boot menu next.