Now let's make all easier for this issue. Detect your USB device...
Be sure the USB drive has bootable flag enable:
[mythcat@desk ~]$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT ... sdb 8:16 1 984M 0 disk └─sdb1 8:17 1 983M 0 part
Umount your USB drive, do not remove it.
[mythcat@desk Downloads]$ sudo fdisk /dev/sdb Welcome to fdisk (util-linux 2.34). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): a Selected partition 1 The bootable flag on partition 1 is disabled now. Command (m for help): a Selected partition 1 The bootable flag on partition 1 is enabled now. Command (m for help): q
Copy the Fedora file image iso to the USB device with the dd command:
[mythcat@desk ~]$ sudo umount /dev/sdb
You can test it with the qemu tool:
[mythcat@desk ~]$ sudo dd if=Fedora-Server-netinst-x86_64-31-1.9.iso of=/dev/sdb 1331200+0 records in 1331200+0 records out 681574400 bytes (682 MB, 650 MiB) copied, 383.766 s, 1.8 MB/s
[mythcat@desk ~]$ sudo qemu-system-x86_64 -hda /dev/sdb