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When working with multiple Linux machines, you often need to copy your SSH keys between systems to enable password-less authentication. This process involves securely transferring your public key from one machine to another and properly configuring the target machine to accept your key for authentication. SSH keys consist of a private key (kept secret on your local machine) and a public key (shared with remote machines). The public key is added to the target machine's authorized_keys file, allowing secure authentication without passwords. SSH Key Structure On your local machine, SSH keys are stored in the .ssh directory ... Read More
PHP-FPM (FastCGI Process Manager) is a popular implementation of PHP that provides significant performance improvements over traditional PHP implementations. When combined with Nginx, it creates a powerful web server stack for high-traffic applications. The built-in status monitoring capabilities of PHP-FPM allow administrators to track process health and performance in real-time. Enabling PHP-FPM Status Page PHP-FPM includes a built-in status page that provides real-time information about process states, memory usage, and request statistics. To enable this feature, first locate and edit the PHP-FPM pool configuration file. Step 1: Configure PHP-FPM Pool Open the PHP-FPM pool configuration file. ... Read More
PostgreSQL is a powerful open-source relational database management system that provides various features including data export capabilities. One of the most common export formats is CSV (Comma-Separated Values), which allows easy data exchange between different applications and systems. CSV is a simple file format where each row represents a record and fields are separated by commas. The first row typically contains column headers, making the data structure clear and readable. Importance of Exporting PostgreSQL Tables to CSV Exporting PostgreSQL tables to CSV format offers several advantages − Data Sharing − Share data with team members ... Read More
Extracting the last directory or file name from a given path is a common task in shell scripting and Linux command-line operations. For example, from the path /tmp/dir/target, we want to extract target as the final component. While this seems straightforward, there are several edge cases that can cause simple solutions to fail, such as trailing slashes, root directory paths, and filenames containing spaces. Common Solutions Since Linux filesystems use forward slashes (/) as path separators and don't allow slashes in filenames, we can treat the path as slash-separated components and extract the last non-empty element. ... Read More
Docker containers are isolated environments that run applications separately from the host system. While this isolation provides security and consistency, there are legitimate scenarios where containers need to access host resources such as databases, files, or services. This article explores various methods to establish connectivity between Docker containers and host system resources. Host Network Access The simplest approach is to configure containers to use the host network directly. This removes network isolation and allows the container to access all host services as if running natively on the host. docker run --network=host my-container Use case: ... Read More
Clustering systems are similar to parallel systems as they both have multiple CPUs. However, a major difference is that clustered systems are created by two or more individual computer systems merged together. The primary goal is to provide high availability and fault tolerance by distributing workload across multiple nodes. There are two main types of clustering systems: asymmetric and symmetric clustering systems. Asymmetric Clustering System In an asymmetric clustering system, one node acts as the primary server that runs all applications, while one or more nodes remain in hot standby mode. The standby nodes continuously monitor the primary ... Read More
The critical section problem occurs when multiple processes access shared resources concurrently. A critical section is a code segment where shared variables can be accessed. To maintain data consistency, only one process can execute in its critical section at a time — this requires an atomic operation. All other processes must wait to execute in their critical sections. Critical Section Structure Process 1 Entry Section Critical Section ... Read More
When working with a Unix-based operating system such as Linux or macOS, it is common to encounter situations where a process becomes unresponsive or needs to be terminated for some reason. Fortunately, there are several command-line utilities available that allow users to end processes in a variety of ways. In this article, we will explore three of the most commonly used utilities for terminating processes: kill, pkill, and killall. We will cover their basic usage, common options, and examples of how they can be used to manage processes on a Unix system. Basic Usage of kill, pkill, and killall ... Read More
Firewalld is a dynamic firewall management tool for CentOS 7 that provides a user-friendly interface to configure and manage firewall rules. Unlike traditional iptables, firewalld supports network zones and allows changes without restarting the entire firewall service. This article demonstrates how to enable and effectively use firewalld on CentOS 7. Installation and Setup Firewalld is included with CentOS 7 but may not be enabled by default. First, check if firewalld is installed and running − sudo systemctl status firewalld To enable and start the firewalld service − sudo systemctl enable firewalld sudo ... Read More
Tar.gz files, also known as "tarballs, " are compressed archive files commonly used in Linux and Unix-based operating systems. A tarball contains one or more files or directories compressed using the gzip algorithm, significantly reducing file size. They serve two main purposes: efficient data transfer between systems and storage of file backups in a single, manageable archive. Understanding the Linux Command Line The Linux command line interface (CLI) provides a powerful text-based method for interacting with your system. To access the terminal, press Ctrl+Alt+T or find it in your applications menu. Once open, you'll see a prompt like ... Read More