Instead of using the last stable Fedora release (F21), I opt for the Rawhide (F22) release. You can download the nightly image ISO. Note that this is a network installation image, hence the small image size of 500-plus MB.
The nightly image is quite buggy and installer may not work. If you stuck with the nightly image, consider trying the Alpha pre-release image instead.
To reduce the download time, we'll use Aria2, a console downloader program that support multiple parallel HTTP connections. On the safe side, we're using a maximum 4 connections per server (-x 4), the default is 1. You can use different value but your mileage may vary. Also, it's considered a poor etiquette to make too many connections.
$ aria2c -x 4 -o fedora_rawhide_f22.iso http://download.fedoraproject.org/pub/fedora/linux/development/rawhide/x86_64/os/images/boot.iso
Plug in your USB thumbdrive. Check the device name using the lsblk command to list the available block devices. This is currently my go-to command to see all available devices and partitions. As we can see below, the device name for USB thumbdrive is /dev/sdb.
$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 119.2G 0 disk ├─sda1 8:1 0 499M 0 part ├─sda2 8:2 0 300M 0 part /boot/efi ├─sda3 8:3 0 128M 0 part ├─sda4 8:4 0 96.3G 0 part / ├─sda5 8:5 0 17.3G 0 part ├─sda6 8:6 0 1G 0 part └─sda7 8:7 0 3.8G 0 part └─cryptswap1 252:0 0 3.8G 0 crypt [SWAP] sdb 8:16 1 7.5G 0 disk └─sdb1 8:17 1 7.5G 0 part
Let's burn the ISO image using the dd command. Roughly around 1 minute and 22 seconds.
$ time sudo dd if=fedora_22_boot.iso of=/dev/sdb bs=4M 138+1 records in 138+1 records out 579862528 bytes (580 MB) copied, 80.0856 s, 7.2 MB/s real 1m20.113s user 0m0.016s sys 0m5.256s
To verify that we've burned the image successfully, we can test it using a virtual machine like QEMU (Quick Emulator) instead on the intended physical machine. Note that this is under Ubuntu 15.04 Vivid Vervet.
$ sudo apt-get install qemu $ sudo qemu-system-x86_64 -hda /dev/sdb -m 1024 -vga std
If you can see result from below screenshot, then you've successfully burn the ISO to the USB thumbdrive.