I call a Node script from PHP on my Ubuntu web server, as in

// The following PHP executes in the context of the Apache user - 'www-data'
$execstring = "node " . $args;
exec($execstring, $output, $return_value);

As noted, the PHP code executes in the context of the Apache user, which is www-data by default on Ubuntu.

I would like to be able to use nvm to switch Node versions for the www-data user.

(Note: I might be able to switch Node versions without using nvm by specifying the full path to a different Node installation - I have not tried this yet, but it's not my question.)

Following instructions here, I install and use nvm quite easily for other users:

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.0/install.sh | bash


nvm install 4.1.2

I have found that I must install nvm separately for every user. This means that nvm does not install for the www-data user when I run the command above as the login user (ubuntu); and, conversely, switching my Node version for the login user (ubuntu) has no effect on the www-data user.

One more important detail: The www-data user is special. This user has severely restricted functionality. To switch to the www-data user in the shell, this special command is required:

sudo su www-data -s /bin/sh 

(...And even the above command won't work without other, previous special steps, not noted here, to allow a shell prompt for the www-data user.)

When logged in as the www-data user, however, although I seem to be able to install nvm using the command noted previously, I cannot run nvm. (The error is nvm not found.)

Attempting to overcome this, I made the brutal mistake of following the suggestion here to attempt to switch the Node version globally (i.e., for all users) while logged in as (I think, but forget now) the root user (oops!):

// Danger!  Do not do this!
n=$(which node);n=${n%/bin/node}; chmod -R 755 $n/bin/*; sudo cp -r $n/{bin,lib,share} /usr/local

Unfortunately, running the above command caused my sudo access to break, and now I must apparently rebuild the server from scratch.

My question is: How can I install and use nvm as the Apache user (www-data) to allow a web server to run a Node process of a given version, and thereby control which version of Node the web server accesses - with the convenience of using nvm?


Short answer: you can't.

NVM is a shell script that only just sets environment variables (mainly modifying your PATH) to change the active node version. As such, they are not persistent beyond the lifetime or process tree of the calling shell.

While you should be able to run your web server with particular environment variables, you can't use NVM to manage them since any call to nvm would be called in a subprocess of your web server and discarded as soon as the command terminates.

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