Creating a Linux boot drive on a MAC for a Kangaroo Mobile pC install I was trying to use your method to create a USB on my Mac for a Linux boot USB to install linux on a Kangaroo mobile pc.  Here is my process:
I tried this with several iterations.  My results are below.  The final result has me stopped.  Any ideas?

Russells-MacBook-Air:~ russellduggan$ sudo dd if=~/Desktop/linuxmint.iso of=/dev/sdx oflag=direct bs=1048576
Password:
dd: unknown operand oflag
Russells-MacBook-Air:~ russellduggan$ terminal&gt;
-bash: syntax error near unexpected token `newline'
Russells-MacBook-Air:~ russellduggan$ cd terminal
-bash: cd: terminal: No such file or directory
Russells-MacBook-Air:~ russellduggan$ 
Russells-MacBook-Air:~ russellduggan$ terminal
-bash: terminal: command not found
Russells-MacBook-Air:~ russellduggan$ sudo dd if=~/Desktop/linuxmint.iso of=/dev/sdx bs=1048576
Password:
dd: /Users/russellduggan/Desktop/linuxmint.iso: No such file or directory
Russells-MacBook-Air:~ russellduggan$ sudo dd if=~/Desktop/linuxmint-18.2-cinnamon-64bit.iso of=/dev/sdx bs=1048576
dd: /dev/sdx: Operation not permitted
Russells-MacBook-Air:~ russellduggan$ 


As you can see I kind of reached an impasse at the last.  Any suggestions you might have I would appreciate.
In your dd command,  

sudo dd if=~/Desktop/linuxmint.iso of=/dev/sdx bs=1048576


/dev/sdx for the output is incorrect.   


This is a Linux convention, not macOS; use /dev/diskX.  
X is the specific disk identifier.  If you are using instructions from a Linux site, they are most likely providing the instructions for doing this on Linux (not macOS) using X as a variable for the specific identifier since the identifier can be different for each user and/or instance as the device is removable.


In Linux it's /dev/sda, /dev/sdb, etc.  In macOS/BSD is /dev/disk1, /dev/disk2, etc.

Also (thanks to user3439894 via comments) you need to make sure you disk is unmonted but not ejected.  Do this by issuing the command diskutil unmountDisk /dev/diskX where X is the number of your disk identifier.