When you run npm install and it tries to install a native package like bcrypt and you see an error message like this:
gyp ERR! build error gyp ERR! stack Error: not found: make gyp ERR! stack at getNotFoundError (/usr/lib/node_modules/npm/node_modules/which/which.js:13:12) gyp ERR! stack at F (/usr/lib/node_modules/npm/node_modules/which/which.js:68:19) gyp ERR! stack at E (/usr/lib/node_modules/npm/node_modules/which/which.js:80:29) gyp ERR! stack at /usr/lib/node_modules/npm/node_modules/which/which.js:89:16 gyp ERR! stack at /usr/lib/node_modules/npm/node_modules/isexe/index.js:42:5 gyp ERR! stack at /usr/lib/node_modules/npm/node_modules/isexe/mode.js:8:5 gyp ERR! stack at FSReqWrap.oncomplete (fs.js:182:21)
you simple need to install GNU Make. On Ubuntu, the easiest way of doing this is to run
sudo apt install build-essential
This will not only install make but also related tools like gcc and some standard header files and tools.