There are two ways of authenticating to a server with SSH: user/password based authentication (which is now by many considered outdated and insecure) and key pair based authentication. Let’s start from the legacy one and build up to the modern way of doing things:
In this version, all you will need to to connect to your server is to run
Continue readingI have written this guide for developers who might be superficially familiar with the basics of SSH – maybe even fiddled with a file or two without really knowing what’s going on – and would like a more cohesive overview of its most powerful features.
This is essentially an organised collection of the main gotchas and topics that gave me (a dev, not a sysadmin) the most dexterity in jumping about from machine to machine in the cloud.
It is meant to be read in succession as each topic builds on the previous, but I also tried to keep them loosely coupled in case the reader is only interested in a particular section.
Have fun.
Disclaimer: This does not mean to be a complete list of all that is possible with SSH. That would probably take a book. Or two. But any feedback about additions is welcome.
SSH is a protocol built on top of TCP that is intended to provide a secure channel for a client and a server to communicate. In its implementation, it consists of two programs:
Continue readingI have recently come across a nasty Too many open files error, and noticed the information on the internet about what that might mean or how to solve it doesn’t always paint a clear picture.
Here I try to put together a more complete guide by gathering all the resources I found as I was dealing with the issue myself.
In Unix-like systems, each process is associated with sets of usage limits, which specify the amount of system
resources they can use. One of those is the limit of open file descriptors (RLIMIT_NOFILE).
But what is a file descriptor?
Continue readingHere is a quick snippet I use all the time when I want to set up an HTTP server on the fly, without leaving the comfort of my terminal.
This is the command:
$ while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; echo "Hello World"} | nc -l 3000; done
Warning: this will block your current terminal.
You will see the following output as you receive requests:
GET / HTTP/1.1 Host: localhost:3000 User-Agent: curl/7.54.0 Accept: */*
If you want your terminal back, or for any other reason want to put the command in the background while it is running, simply press ctrl+z
When you are done and want to kill the background process, you can do so with
$ kill %1
This will start a simple server on port 3000.
Save to a file index.js
var http = require('http');
console.log("Server listening on port 3000");
http.createServer((req, res) => {
console.log("Got a request");
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end("Hello World!");
}).listen(3000);
Run with:
$ node index.js
Output:
Server listening on port 3000