Dimas Maulana

Author: NIXCRAFT
Published Date: October 16, 2006
Last Updated: October 16, 2006
Category: HOWTO, TIPS, TROUBLESHOOTING

If you’ve experienced your OpenSSH server connection dropping out after a few minutes or a specific period of inactivity, don’t worry; it’s not a bug but rather a security feature. This behavior is usually due to a packet filter or NAT (Network Address Translation) device timing out your TCP connection as a security measure. This issue typically occurs when using SSH protocol version 2.

Securing your OwnCloud server is crucial to protect your data from potential threats. In this guide, we will focus on two key aspects: automatically installing security updates and preventing brute-force password hacking attempts.

Automatically Install Security Updates

No software package is flawless, and security vulnerabilities may exist in your server’s software stack, from the Linux kernel to the SSL library. However, many of these vulnerabilities have patches available, and the primary reason they get exploited is due to delayed or neglected security updates.

File permissions in Ubuntu and other Unix-like operating systems are crucial for controlling access to files and directories. They determine who can read, write, or execute a file or directory. You can use the ls command with the -l option to display detailed information about file permissions. Here’s what each part of the output means:

ls -l /path/to/file
-rwxr-xr-x 1 10490 floppy 17242 May  8  2013 acroread

1. The first character - represents the type of object it is. Here, it’s a regular file. Other possible values include:
   • d: Directory
   • c: Character device
   • l: Symbolic link
   • p: Named pipe (FIFO)
   • s: Socket
   • b: Block device
   • D: Door (door file)
   • -: Regular file

The next three characters rwx represent permissions for the owner of the file. Specifically:

In this guide, we will walk through the steps to install and configure DDClient on Ubuntu 14.04 LTS to work with CloudFlare. DDClient is a dynamic DNS update client that allows you to automatically update your DNS records on CloudFlare when your IP address changes. This can be useful if you are hosting a server on a dynamic IP address.

Prerequisites

Before you begin, make sure you have the following:

It’s important to be cautious when using the killall command, especially with sudo, as it can terminate processes indiscriminately. Killing SSH connections might disrupt legitimate connections and potentially cause issues.

If you need to terminate specific SSH tunneling connections, it’s better to identify the process IDs (PIDs) associated with those connections and then use kill with the specific PIDs. Here’s a safer way to do it:

1. List SSH Processes: First, list the SSH processes to identify the ones you want to terminate. You can use the ps command with grep to filter SSH processes:

User management is an essential part of maintaining a secure and organized Ubuntu system. This guide provides you with various commands and procedures for managing users on your Ubuntu system.

Listing All Users

To list all users on your system, you can use the following command: