第一步 指定版本源
执行 curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
setup_5.x 需要安装的版本号，替换数字就行。

vagrant@ubuntu-xenial:~$ curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -

// 出现这个就说明正在成功安装了！

## Installing the NodeSource Node.js v6.x repo...

## Populating apt-get cache...

+ apt-get update

Hit:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial InRelease

Get:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-updates InRelease [95.7 kB]

Get:3 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease [92.2 kB]

Get:4 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-security InRelease [94.5 kB]

Hit:5 http://repo.mysql.com/apt/ubuntu xenial InRelease

Fetched 282 kB in 0s (615 kB/s)

Reading package lists... Done

## Confirming "xenial" is supported...

+ curl -sLf -o /dev/null 'https://deb.nodesource.com/node_6.x/dists/xenial/Release'

## Adding the NodeSource signing key to your keyring...

+ curl -s https://deb.nodesource.com/gpgkey/nodesource.gpg.key | apt-key add -

OK

## Creating apt sources list file for the NodeSource Node.js v6.x repo...

+ echo 'deb https://deb.nodesource.com/node_6.x xenial main' > /etc/apt/sources.list.d/nodesource.list

+ echo 'deb-src https://deb.nodesource.com/node_6.x xenial main' >> /etc/apt/sources.list.d/nodesource.list

## Running `apt-get update` for you...

+ apt-get update

Hit:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial InRelease

Get:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-updates InRelease [95.7 kB]

Get:3 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease [92.2 kB]

Get:4 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-security InRelease [94.5 kB]

Hit:5 http://repo.mysql.com/apt/ubuntu xenial InRelease

Get:6 https://deb.nodesource.com/node_6.x xenial InRelease [3,914 B]

Get:7 https://deb.nodesource.com/node_6.x xenial/main Sources [765 B]

Get:8 https://deb.nodesource.com/node_6.x xenial/main amd64 Packages [960 B]

Get:9 https://deb.nodesource.com/node_6.x xenial/main i386 Packages [959 B]

Fetched 289 kB in 5s (51.9 kB/s)

Reading package lists... Done

## Run `apt-get install nodejs` (as root) to install Node.js v6.x and npm

第二步
安装 nodejs，执行 apt-get install nodejs !

vagrant@ubuntu-xenial:~$ sudo apt-get install nodejs

Reading package lists... Done

Building dependency tree

Reading state information... Done

The following NEW packages will be installed:

  nodejs

0 upgraded, 1 newly installed, 0 to remove and 90 not upgraded.

Need to get 10.1 MB of archives.

After this operation, 50.7 MB of additional disk space will be used.

Get:1 https://deb.nodesource.com/node_6.x xenial/main amd64 nodejs amd64 6.9.1-1nodesource1~xenial1 [10.1 MB]

Fetched 10.1 MB in 1min 25s (119 kB/s)

Selecting previously unselected package nodejs.

(Reading database ... 60366 files and directories currently installed.)

Preparing to unpack .../nodejs_6.9.1-1nodesource1~xenial1_amd64.deb ...

Unpacking nodejs (6.9.1-1nodesource1~xenial1) ...

Processing triggers for man-db (2.7.5-1) ...

Setting up nodejs (6.9.1-1nodesource1~xenial1) ...

vagrant@ubuntu-xenial:~$ node -v

v6.9.1

vagrant@ubuntu-xenial:~$ npm -v

3.10.8