Remote X11 connections allow a user to launch graphical applications on a remote server and have the windows display securely on their local machine. To enable this functionality, the X11 forwarding feature must be enabled in the SSH daemon on the remote server. Common methods to achieve this include editing the /etc/ssh/sshd_config file to set…
The X Window System (X11) allows graphical applications to securely display their interfaces on both local and remote machines over the network. However, improperly configured X11 connections can pose security risks by allowing unauthorized remote hosts to access and control local graphical sessions. Administrators can leverage tools like xhost and Xauthority to selectively grant, restrict,…
Getting Started with Tmux Installing and launching tmux Tmux is a terminal multiplexer that allows multiple terminal sessions to be accessed simultaneously in a single window. To get started with tmux, first install it on your system with your package manager of choice. On Linux: $ sudo apt install tmux #Ubuntu/Debian $ sudo yum install…
The Problem: Inconsistent Variable Usage Shell scripts allow variables to be accessed with or without braces (e.g. $foo vs ${foo}). This flexibility can lead to inconsistencies and unexpected behavior if not used carefully. Using braces around variables provides clarity, avoids naming conflicts, and enables more robust usage. Benefits of Using Braces Using braces { and…
What are Interactive and Non-Interactive Shells? An interactive shell allows a user to directly execute commands and view output in real-time. Common examples include bash, zsh, and other Linux/UNIX shells accessed via a terminal or command line interface. Users can explore data, prototype code, and convenient everyday tasks through immediate feedback. A non-interactive shell executes…
Overcoming Network Latency for Remote Unix Apps A core challenge when accessing Unix applications over a network is the laggy responsiveness that results from communication delays between the client and server. This network latency reduces the interactivity of applications, harming user productivity. However, there are techniques across the network stack, application layer, and end-user experience…
Understanding Standard Input and Output The standard input (stdin), standard output (stdout), and standard error (stderr) are three data streams that are associated with every Unix process. The stdin stream provides input data to a process, stdout streams output data from a process, and stderr streams error data from a process. The stdin stream corresponds…
Escaping Special Characters in Filenames Filenames containing special characters like spaces, asterisks, and parentheses can cause errors when used with commands in shells like Bash. The shell attempts to interpret these characters instead of treating them as literals which leads to unintended behavior. For example, an asterisk is used to wildcard match any characters in…
The Perils of Unquoted Braces Brace expansion in shell scripts refers to the process whereby curly braces=”{}” containing commas-separated strings are expanded into the individual strings. For example, echo {file1,file2} will expand to echo file1 file2. This can cause significant issues when used with unsafe variables in scripts. How unquoted braces enable unintended file globbing…
Code injection attacks take advantage of vulnerabilities in web applications to inject malicious code. This code gets executed by the application and allows the attacker to access resources or data that they should not have access to. Code injection can lead to data theft, corruption, or deletion. Some common examples include SQL injection, OS command…