Code Tips

How can I add a user to a group under Linux operating system using command line options? How to add an existing user into a group in Linux using command line options?

Fsutil.exe is a built in filesystem tool that is useful to do file system related operations from command line. We can create a file of required size using this tool.

The Context element represents a web application, which is run within a particular virtual host. Each web application is based on a Web Application Archive (WAR) file, or a corresponding directory containing the corresponding unpacked contents, as described in the Servlet Specification (version 2.2 or later).

Add a file called ROOT.xml in $CATALINA_BASE/conf/Catalina/localhost/

To implement IP filtering Tomcat offers the RemoteAddrValve class for filtering on IP and the RemoteHostValve for filtering on host name.

There are several worms which attempt to exploit vulnerable SSH servers, by logging in to a host with a collection of usernames and passwords such as "admin/admin", "test/test", "root/root", etc. These shouldn't be of much concern if you're keeping good passwords, but there are simple ways to prevent them regardless.

To limit ssh access to a linux box based on originating IP address, edit /etc/hosts.allow:

CSR and SSL Certificate Installation in Tomcat Web Server

Java Keytool is a key and certificate management utility. It allows users to manage their own public/private key pairs and certificates. It also allows users to cache certificates. Java Keytool stores the keys and certificates in what is called a keystore. By default the Java keystore is implemented as a file. It protects private keys with a password. A Keytool keystore contains the private key and any certificates necessary to complete a chain of trust and establish the trustworthiness of the primary certificate.

Even the best coders make mistakes sometimes. When it comes to the markup language HTML, there are some mistakes that are more common than others. You should try and avoid these.

Linux comes with a host based firewall called Netfilter

If you want to use cURL with HTTPS in Windows, you can setup it easily

How do I set advanced security options of the TCP/IP stack and virtual memory to improve security and performance of my system? How do I configure Linux kernel to prevent certain kinds of attacks using /etc/sysctl.conf? How do I set Linux kernel parameters?

How do I configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux?

Amazon's EC2 is a really great platform for well, everything!

We block access to production MySQL servers over port 3306 for security reasons. Here is an example, use ssh tunnel to remote MySQL, connection string that proxies localhost port 13306 to port 3306 on the target system (port forwarding)

Are you using MySQL's utf8 charset in your databases? In this write-up I'll explain why you should switch to utf8mb4 instead, and how to do it.