Javascript

Problem:

When you try to run any npm command such as npm start , you see an error message such as

/usr/lib/node_modules/npm/lib/es6/validate-engines.js:31
    throw err
    ^

TypeError: Class extends value undefined is not a constructor or null
    at Object.<anonymous> (/usr/lib/node_modules/npm/node_modules/fs-minipass/lib/index.js:136:4)
    at Module._compile (node:internal/modules/cjs/loader:1233:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1287:10)
    at Module.load (node:internal/modules/cjs/loader:1091:32)
    at Module._load (node:internal/modules/cjs/loader:938:12)
    at Module.require (node:internal/modules/cjs/loader:1115:19)
    at require (node:internal/modules/helpers:119:18)
    at Object.<anonymous> (/usr/lib/node_modules/npm/node_modules/cacache/lib/content/read.js:4:13)
    at Module._compile (node:internal/modules/cjs/loader:1233:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1287:10)

Solution:

This is an internal error in npm or packages required by npm. Typically, it is caused by an incomplete update of NodeJS and npm which leaves npm or its dependencies in a broken state.

The solution is to reinstall NodeJS:

• Uninstall NodeJS using a command such as

  sudo apt remove nodejs

• Remove the NodeJS package folder entirely, on Linux it can be moved to a backup location using e.g.

  sudo mv /usr/lib/node_modules ~/node_modules_backup

• Re-installing NodeJS using a command such as

  sudo apt -y install nodejs

• Re-installing any globally installed packages you need, such as npm i -g @angular/cli

As of version v13.1.0, node-ssh does not support generating SSH keys by its own.

However, you can use the ssh2 library which is already used internally by node-ssh.

See our post How to generate SSH public & private key in NodeJS using ssh2 library for more details.

The following code is a Promise based wrapper around ssh2’s utils.generateKeyPair():

const { utils: { generateKeyPair } } = require('ssh2');
const {writeFile} = require('fs/promises');

/**
 * ssh2's generateKeyPair as promise
 */
function SSHGenerateKeyPairPromise(keytype="ed25519", opts = {}) {
    return new Promise((resolve, reject) => {
        generateKeyPair(
            keytype, opts,
            (err, keys) => {
                if (err) { return reject(err) };
                return resolve(keys);
            }
        );
    });
}

/**
 * Run SSHGenerateKeyPairPromise() and save the keys to
 * opts.privateKeyPath and opts.publicKeyPath
 * @returns The generated keys
 */
async function SSHGenerateAndSaveKeyPairPromise(keytype="ed25519", opts = {}) {
    // Check if opts.privateKeyPath and opts.publicKeyPath are set
    if (!opts.privateKeyPath || !opts.publicKeyPath) {
        throw new Error("opts.privateKeyPath and opts.publicKeyPath must be set");
    }
    const keys = await SSHGenerateKeyPairPromise(keytype, opts);
    //Save keys to opts.privateKeyPath and opts.publicKeyPath using fs.promise
    await writeFile(opts.privateKeyPath, keys.private);
    await writeFile(opts.publicKeyPath, keys.public);
    return keys;
}

Usage example for ed25519 keys:

SSHGenerateAndSaveKeyPairPromise('ed25519', {
    privateKeyPath: 'id_ed25519',
    publicKeyPath: 'id_ed25519.pub'
}).then(keys => {
    console.log("Successfully generated ed25519 keys");
}).catch(err => {
    console.log(err);
});

Usage example for rsa keys:

SSHGenerateAndSaveKeyPairPromise('rsa', {
    bits: 8192,
    privateKeyPath: 'id_rsa',
    publicKeyPath: 'id_rsa.pub'
}).then(keys => {
    console.log("Successfully generated RSA keys");
}).catch(err => {
    console.log(err);
});

My NodeJS app using the argon2 library crashed within my docker container (the process just exited without an error message) every time I used argon2 funtions, even though it worked fine on my Desktop.

This error occured with argon2==0.30.3. I fixed it by downgrading it to 0.26.2 using the following statement in package.json:

"argon2": "^0.26.2",

With the correct version installed (don’t forget to npm install after changing package.json), the issue disappeared entirely. I did not try any other versions of argon2.

When you are running a NodeJS server inside a docker container, you will often encouter the issue that the container does not shutdown properly but taking a long time (several minutes) to shutdown.

In order to fix this, add the following code to your main NodeJS file (typically you should add it at the top of the file to make sure nothing prevents it from getting executed)

process.on('SIGTERM', function() {
  console.log('SIGTERM received, shutting down...');
  process.exit(0);
});
process.on('SIGINT', function() {
  console.log('SIGINT received, shutting down...');
  process.exit(0);
});

This will force NodeJS to exit (more or less immediately) once either SIGINT or SIGTERM is received. Typically, Docker sends SIGTERM on container shutdown.

Background information

See this GitHub guide

Problem:

While trying to rename a file using fs.move() in NodeJS, you see an error message such as

Error: EXDEV: cross-device link not permitted, rename '/tmp/upload_8a8c71784abf9942b40c1359935b1997' -> 'myfile.pdf'

Solution:

This error occurs because you are moving a file from one drive (/tmp in our example above) to another drive (the current directory in our example above). On most platforms, this can’t be done using a simple rename operation.

Instead, fs.copyFile() the file.

For example, instead of

await fs.move('/tmp/upload_8a8c71784abf9942b40c1359935b1997', 'myfile.pdf')

first, copy the file:

await fs.copyFile('/tmp/upload_8a8c71784abf9942b40c1359935b1997', 'myfile.pdf')

and then – if desired – remove the source file to mirror the behaviour of os.move() as closely as possible.

await fs.remove('/tmp/upload_8a8c71784abf9942b40c1359935b1997', 'myfile.pdf')
await fs.unlink('/tmp/upload_8a8c71784abf9942b40c1359935b1997')