$ sudo apt-get update && sudo apt-get install --no-install-recommends yarn
--> Because I used NVM to install NodeJS, I Added "--no-install-recommends".
...
Recommended packages:
nodejs
The following NEW packages will be installed:
yarn
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 697 kB of archives.
After this operation, 4,436 kB of additional disk space will be used.
Get:1 https://dl.yarnpkg.com/debian stable/main amd64 yarn all 1.7.0-1 [697 kB]
Fetched 697 kB in 1s (1,105 kB/s)
Selecting previously unselected package yarn.
(Reading database ... 166162 files and directories currently installed.)
Preparing to unpack .../archives/yarn_1.7.0-1_all.deb ...
Unpacking yarn (1.7.0-1) ...
Setting up yarn (1.7.0-1) ...
...