Linux: Writing .img / .iso files to USB drive or SD card

Determine what device your USB/SD is. With your USB plugged in run:
sudo ls -l /dev/disk/by-id/*usb*

This should produce output along the lines of:

lrwxrwxrwx 1 root root 9 2010-03-15 22:54 /dev/disk/by-id/usb-_USB_DISK_2.0_077508380189-0:0 -> ../../sdc
lrwxrwxrwx 1 root root 10 2010-03-15 22:54 /dev/disk/by-id/usb-_USB_DISK_2.0_077508380189-0:0-part1 -> ../../sdc1

In this example output, the external device is sdc

You can also use df if the usb drive have been automounted
df -h
and then umount to free the drive, example
umount /media/username/usbdrive

Now, we’re going to put the .img or .iso file
sudo dd if=filename.iso of=/dev/sdb bs=8M; sync
sudo dd if=filename.iso of=/dev/usbdevice bs=8M | sync

bs=8M is used to speed up the prosess, by reading/writing in chunks of 8MB (espesially usefull when writing to a usb 3.0 drive or a normal harddrive).

NOTE – Be sure to remember that there is never a trailing number on the end of your /dev/sdx USB device