MAC stands for Media Access Control — a six-byte identifier (usually written as twelve hexadecimal digits) that uniquely identifies a network interface on a LAN. The Address Resolution Protocol (ARP) maps IP addresses to MAC addresses at layer 2. You might need to change your MAC address to: Bypass network access controls tied to MAC…
You may need to prevent certain packages from being updated during system maintenance—the kernel on production servers, or specific library versions you’ve carefully tuned. When you run dnf update or yum update, you want those packages skipped entirely. The solution is straightforward: add an exclusion to DNF or YUM’s configuration file. Configuration Syntax Add this…
Port forwarding allows external hosts to reach services inside a private network by mapping traffic from a public address to an internal one. On Linux, this is implemented through iptables rules that modify packet headers as they traverse the kernel’s netfilter framework. Common use cases include exposing HTTP/HTTPS servers from a private LAN to the…
tmpfs delivers exceptional I/O performance since it lives entirely in RAM. Exporting it via NFS can be useful for temporary caches, build artifacts, or high-speed data sharing between systems on a trusted network. The catch: NFS needs additional configuration to export pseudo-filesystems like /dev/shm. Without the right settings, you’ll hit access denied errors or fsid…
On Fedora/RHEL-based systems: dnf install ecryptfs-utils On Debian/Ubuntu: apt-get install ecryptfs-utils Load the kernel module modprobe ecryptfs To ensure the module loads automatically on boot, add it to /etc/modules-load.d/: echo “ecryptfs” | sudo tee /etc/modules-load.d/ecryptfs.conf Create directories You’ll need two directories: one for encrypted storage (.private) and one as the mount point (private). The .private…
Xen remains a production hypervisor for enterprise deployments (AWS EC2, Citrix Hypervisor), though KVM has become the default for most Linux distributions. If you’re deploying Xen in 2026, you’ll likely be working with recent stable releases rather than the legacy versions covered in older guides. This guide covers building a modern Xen Dom0 environment on…
The rpm and dnf commands let you inspect exactly which files a package installed and find the package that owns a specific file. These queries work on both the host system and inside containers like Toolbox or Distrobox. List Files from an Installed Package rpm -ql package-name This recursively lists all files and directories the…
rsync is a reliable choice for backing up your Linux home directory, especially when dealing with large files and incremental changes. Unlike git (which struggles with files >5GB), rsync efficiently handles large files and only transfers what’s changed on subsequent runs. Basic Backup Command The fundamental syntax is straightforward: rsync -avxP \ /path/to/directory/to/backup \ /path/to/directory/for/storing/backup…
If you don’t already have a key pair, use Ed25519 — it’s faster and more secure than RSA: ssh-keygen -t ed25519 -C “your_email@example.com” For older systems that don’t support Ed25519, RSA with 4096 bits still works: ssh-keygen -t rsa -b 4096 Keys are stored in ~/.ssh/ by default: id_ed25519 (private) and id_ed25519.pub (public) for Ed25519,…
sshfs is the standard tool for mounting remote filesystems over SSH. It’s available in most distribution repositories. Debian/Ubuntu: sudo apt install sshfs RHEL/CentOS/Fedora: sudo dnf install sshfs Alpine: apk add sshfs On some systems you may need to ensure the fuse kernel module is loaded: sudo modprobe fuse Basic Mount Mount a remote directory to…
The mailx (or s-nail on modern distributions) command remains useful for scripted email delivery, particularly when you need to send alerts or notifications automatically. Gmail’s SMTP service works well for this, though it requires TLS authentication and specific configuration. Prerequisites Most Linux distributions include mailx or s-nail by default. On systems using s-nail (Ubuntu 20.04+,…
A Linux box serving as a network gateway needs two network interfaces: eth0: Connected to the local network (LAN) with IP 192.168.0.1 eth1: Connected to the upstream network (Internet) with IP 198.51.100.1 The goal is to allow clients on the 192.168.0.0/16 network to route traffic through this gateway to reach external networks. Enable IP Forwarding…
SELinux provides mandatory access controls that catch security violations most firewall and file permission rules miss. Before disabling it, exhaust other options — SELinux warnings often reveal real security problems worth understanding. That said, there are legitimate reasons to adjust SELinux: testing application behavior without policy violations, troubleshooting misbehaving software, or running systems where the…
When you need to start long-running commands while continuing to work in the shell, run them in the background. Bash and other modern shells maintain a job list and allow you to switch jobs between foreground and background execution. Only one job can run in the foreground at a time. Starting a Background Job Append…
The default number of loop devices on most Linux systems is 8, which is often insufficient for scenarios like running multiple virtual machines with loop device-backed storage, containerized environments, or disk image management. If you need more than the default allocation, you’ll need to increase max_loop. First, check your current loop device count: losetup -f…
Xen remains a robust hypervisor for production environments—AWS EC2, Citrix Hypervisor, and many hosting providers still rely on it. However, KVM has become the default for most Linux distributions due to simpler management and better integration with standard tooling. For new deployments on standard Linux, evaluate KVM with libvirt or container solutions like Docker and…