Grunt is already installed. but grunt command is not found

Now i am trying to install grunt package via npm.

And successfully installed grunt package.

But when I use grunt command in my cli, it gives me 'grunt' command is not found.

I'm convinced this package installed..

because exist grunt package folder.

/.node/lib/node_modules

• grunt-cli
• grunt-contrib
• mocha
• npm

Here is my local compute information

OS : Ubuntu 14.04.5 LTS

NPM : 4.2.0

Node.js : v7.10.0

Any advice or suggestion would be appreciated

Check the command blow.

npm install -g grunt-cli
npm install -g grunt

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