I'm trying to create a bootable usb for ubuntu 20.04 on ubuntu 12.04

Solution 1:

Create a Bootable USB for Ubuntu 20.04 using Ubuntu 12.04

There are not many options for creating a 20.04 bootable USB using 12.04 besides for dd.

Startup Disk Creator, Unetbootin, Etcher, Gnome-Disks, Ventoy and mkusb* do not work.

Method that works for UEFI boot computers.

• Format the USB drive as either FAT32 or NTFS, FAT32 preferred especially if persistence is in the future..

• In 12.04 Disk Utility, right click your 20.04 ISO file and select Open with Archive Manager.

• Click Extract and select your USB drive.

Once extraction is complete the USB will boot to Ubuntu 20.04 on a UEFI computer.

Method that works for BIOS boot computers.

• Extract the ISO file to USB as above.

• Install grub, if in BIOS mode or booted from USB drive run:

    sudo mount /dev/sdx1 /mnt
  
    sudo grub-install --boot-directory=/mnt/boot /dev/sdx
  

where sdx is your USB drive.

The USB will now boot to Ubuntu 20.04 on a BIOS/Legacy mode computer and a UEFI computer.

(This is almost easier than using Etcher).

*dd via mkusb-min worked okay, see sudodus answer.

Solution 2:

mkusb-min wraps a safety belt around dd.

I will suggest a command-line method with a simple shell-script mkusb-min. It is simple, the shellscript is very small compared to the other versions of mkusb, yet it serves the purpose to wrap a safety belt around dd.

mkusb-min works in old versions of Ubuntu as well as from most other Linux distros. It needs bash, dd, grep, ls, lsblk, sed, sleep, sort, tr, /dev/disk/by-id, some standard tools and features, that were present in almost all current linux distros 2017, and also in Ubuntu 12.04 LTS.

You find instructions when you search the internet with the search string mkusb-min or something similar, or directly with

mkusb minimal shellscript - mkusb-min

There are detailed instructions at that website how to download, check and use mkusb-min.

First you should make it executable

cd Downloads/
sudo chmod +x mkusb-min

You get a short help text when you run the command without any parameters.

sudo ./mkusb-min

or with full path for example

$ sudo /home/penny/Downloads/mkusb-min
 Run 'mkusb-min' with sudo or as root 
               This shellsript wraps a safety belt around 'dd'               
Clone from an iso or image file to a target device (typically a USB pendrive)
Usage:
 sudo /path/mkusb-min <source file> <target device> 
Examples:
 sudo /home/penny/Downloads/mkusb-min file.iso /dev/sdx
 sudo /home/penny/Downloads/mkusb-min file.img /dev/sdx
Help:
/home/penny/Downloads/mkusb-min -h
Version:
/home/penny/Downloads/mkusb-min -v
Available devices (tran-MODEL  device),
 nvme-eui.0026b7282486d045  /dev/nvme0n1 
 nvme-KINGSTON_SA2000M8250G_50026B7282486D04  /dev/nvme0n1 
 ata-SanDisk_SD6SB1M256G1001_143104401008  /dev/sda 
 ata-WDC_WD4002FYYZ-01B7CB1_K3GWHAEB  /dev/sdb 
 usb-SanDisk_Cruzer_Blade_00008126121320014148-0:0  /dev/sdc 
 ata-PLDS_DVD-RW_DH16AESH_S0C19802ZVJ8EZ00N797  /dev/sr0 

In this example the Sandisk USB pendrive at /dev/sdc is a suitable target device.