OpenSSH has two directives for allowing and denying ssh user access. DenyUsers user1 user2 user3 Use to block user login. You can use wild cards as well as [email protected] (user1 is not allowed to login from somedomain.com host) pattern. DenyGroups group1 group2 A list of group names, if user is part of primary of supplementary… Read More »
How To Set Up ProFTPD on Ubuntu 12.04 About ProFTP ProFTPD is a popular ftp server. Because it was written as a powerful and configurable program, it is not necessarily the lightest ftp server available for virtual servers. Warning: FTP is inherently insecure! Consider configuring ProFTPd to use SFTP, a secure alternative to FTP… Read More »
Taken from the original FAQ. 6 Remember that TCP guarantees all data transmitted will be delivered, if at all possible. When you close a socket, the server goes into a TIME_WAIT state, just to be really really sure that all the data has gone through. When a socket is closed, both sides agree by sending… Read More »
Theodore Faber Joe Touch Wei Yue University of Southern California/Information Sciences Institute 4676 Admiralty Way Marina del Rey, CA 90292 Phone: 310-822-1511 {faber,touch,wyue}@isi.edu Abstract Hosts providing important network services such as HTTP and FTP incur a per-connection memory load from TCP that can adversely affect their connection rate and throughput. The memory requirement is… Read More »
When building TCP client server systems it’s easy to make simple mistakes which can severely limit scalability. One of these mistakes is failing to take into account theTIME_WAIT state. In this blog post I’ll explain why TIME_WAIT exists, the problems that it can cause, how you can work around it, and when you shouldn’t. TIME_WAIT… Read More »
How to Use Reprepro for a Secure Package Repository on Ubuntu 14.04 Introduction to Packages and Repositories We’ve all been there – needing a program – and what do we do? Most of us just apt-get install postfix and presto! We magically have Postfix installed. It isn’t really magic, though. The package manager apt-get searches… Read More »
How To Setup and Configure an OpenVPN Server on CentOS 7 Introduction We’re going to install and configure OpenVPN on a CentOS 7 server. We’ll also discuss how to connect a client to the server on Windows, OS X, and Linux. OpenVPN is an open-source VPN application that lets you create and join a… Read More »
Understanding Nginx HTTP Proxying, Load Balancing, Buffering, and Caching Introduction In this guide, we will discuss Nginx’s http proxying capabilities, which allow Nginx to pass requests off to backend http servers for further processing. Nginx is often set up as a reverse proxy solution to help scale out infrastructure or to pass requests to other… Read More »
Understanding the Nginx Configuration File Structure and Configuration Contexts Introduction Nginx is a high performance web server that is responsible for handling the load of some of the largest sites on the internet. It is especially good at handling many concurrent connections and excels at serving static content. While many users are aware of Nginx’s… Read More »
Understanding Nginx Server and Location Block Selection Algorithms Introduction Nginx is one of the most popular web servers in the world. It can successfully handle high loads with many concurrent client connections, and can easily function as a web server, a mail server, or a reverse proxy server. In this guide, we will discuss some… Read More »