Plug in your USB thumbdrive.
For Desktops
Download the Ubuntu 20.04 Desktop LTS .iso file here.
For Servers
Download the Ubuntu 20.04 Server LTS .iso file here.
Linux Instructions for creating a bootable USB image
Now, you’ll need to determine the device name of USB device; it will look something like /dev/sdc. You can use the fdisk command to do this:
$ fdisk -l
Disk /dev/sdb: 232.9 GiB, 250059350016 bytes, 488397168 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: gpt
Disk identifier: 65F1D71B-D087-4A0A-8C50-1A759FCBC20D
Device Start End Sectors Size Type
/dev/sdb1 2048 1050623 1048576 512M EFI System
/dev/sdb2 1050624 471873535 470822912 224.5G Linux filesystem
/dev/sdb3 471873536 488396799 16523264 7.9G Linux swap
Disk /dev/sdc: 7.2 GiB, 7746879488 bytes, 15130624 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: 0x663eb4c4
Device Boot Start End Sectors Size Id Type
/dev/sdc1 * 0 3815135 3815136 1.8G 0 Empty
/dev/sdc2 3737268 3741939 4672 2.3M ef EFI (FAT-12/16/32)
In this case, the thumbdrive is /dev/sdc (I can tell by the storage size). Now, copy .iso file to the USB:
sudo dd bs=16M if=<path to .iso> of=<device name> conv=fdatasync; sync;
You now have a USB that you can use to install Ubuntu 20.04.
MacOS / OSX Instructions for creating a bootable USB image
You’ll need to determine the device name of USB device; it will look something like /dev/sdc. You can use the fdisk command to do this:
$ sudo diskutil list
Disk /dev/disk1: 232.9 GiB, 250059350016 bytes, 488397168 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: gpt
Disk identifier: 65F1D71B-D087-4A0A-8C50-1A759FCBC20D
Device Start End Sectors Size Type
/dev/sdb1 2048 1050623 1048576 512M EFI System
/dev/sdb2 1050624 471873535 470822912 224.5G Linux filesystem
/dev/sdb3 471873536 488396799 16523264 7.9G Linux swap
Disk /dev/disk2: 7.2 GiB, 7746879488 bytes, 15130624 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: 0x663eb4c4
Device Boot Start End Sectors Size Id Type
/dev/sdc1 * 0 3815135 3815136 1.8G 0 Empty
/dev/sdc2 3737268 3741939 4672 2.3M ef EFI (FAT-12/16/32)
In this case, the thumbdrive is /dev/disk2 (I can tell by the storage size). Now, copy with dd the .iso file to the USB:
sudo dd bs=16m if=<path to .iso> of=<device name> && sudo sync
Wait until the sudo sync command returns and you’ll now have a bootable USB!