Intenté instalar nodejs y npm en ubuntu 12.04. Busqué en Google y lo hice. Ahora, no pude instalar npm en la máquina.
sudo apt-get install npm
Lo que me da esto
The following packages have unmet dependencies:
npm : Depends: nodejs but it is not going to be installed
Depends: nodejs-dev
Depends: node-request but it is not going to be installed
Depends: node-mkdirp but it is not going to be installed
Depends: node-minimatch but it is not going to be installed
Depends: node-semver but it is not going to be installed
Depends: node-ini but it is not going to be installed
Depends: node-graceful-fs but it is not going to be installed
Depends: node-abbrev but it is not going to be installed
Depends: node-nopt but it is not going to be installed
Depends: node-fstream but it is not going to be installed
Depends: node-rimraf but it is not going to be installed
Depends: node-tar but it is not going to be installed
Depends: node-which but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
apt-get install npm
hay que evitarlo (!). Compruebe sinpm -v
está allí antes para intentar instalar ... (lea más abajo en la respuesta de @ MarcoCerpi)