i followed your instruction. but still i am facing this error.

js20@js20:~/Desktop/angular2-seed$ npm start

angular2-seed@1.0.0 start /home/js20/Desktop/angular2-seed
npm run server

angular2-seed@1.0.0 server /home/js20/Desktop/angular2-seed
webpack-dev-server --inline --progress --port 3000 --content-base src

sh: 1: webpack-dev-server: not found
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! angular2-seed@1.0.0 server: webpack-dev-server --inline --progress --port 3000 --content-base src
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the angular2-seed@1.0.0 server script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/js20/.npm/_logs/2017-09-29T04_08_16_556Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! angular2-seed@1.0.0 start: npm run server
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the angular2-seed@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/js20/.npm/_logs/2017-09-29T04_08_16_629Z-debug.log

my node version
node = v8.4.0

my npm version
npm = 5.4.2