Master Linux administration, command-line tools, system configuration, and single-machine systems. Explore our full academy at: https://www.systutorials.com/linux-systems-admin-academy/
A hard link is an additional directory entry pointing to the same inode as the original file. Unlike symbolic links, hard links share the same inode number and have identical permissions, ownership, and content. To find all hard links to a file, you need to locate every directory entry with the same inode. Using find…
LVM (Logical Volume Management) abstracts physical storage into logical volumes, giving you flexibility to resize filesystems, snapshot data, and manage disk space without downtime. It sits between your physical disks and the filesystems you mount. The three core LVM concepts are: Physical Volumes (PVs): Physical disks or disk partitions Volume Groups (VGs): Collections of PVs…
When you need to verify that two Linux systems can communicate over a specific protocol and port, you have several solid options. Let’s cover the most practical approaches. Using nc (netcat) The nc command remains a reliable choice for quick connectivity tests. It’s widely available and requires no special setup. TCP connection test To listen…
Evolution is a full-featured personal information management suite that handles email, contacts, calendars, and tasks. It includes enterprise features like native Microsoft Exchange support and integrates deeply with GNOME’s ecosystem. To troubleshoot issues, migrate data, back up configurations, or secure your setup, you need to know where Evolution stores everything. Evolution follows the XDG Base…
Before encoding instructions, you need to understand the two assembly syntaxes you’ll encounter—they differ fundamentally in operand order and addressing format. Intel syntax (Intel/AMD manuals): Operand order: destination, source Memory addressing: [base+offset] Example: add r8, [rdi+0xa] AT&T syntax (GNU toolchains on Linux): Operand order: source, destination Memory addressing: offset(%base) Example: addq 0xa(%rdi), %r8 For most…
When you need to debug kernel behavior without full instrumentation frameworks, module parameters offer a pragmatic shortcut. Rather than immediately reaching for perf, kprobes, or eBPF, you can add simple toggles and state tracking directly in the code you’re investigating, then control them at runtime through sysfs. Frameworks like perf, kprobes, and eBPF are powerful…
USB technology continues evolving with each generation delivering significant speed improvements. Linux provides comprehensive kernel support across all modern standards through dedicated drivers. USB 2.0 Speed: 480 Mbps (theoretical ~60 MB/s) Status: Legacy but still common. Nearly all systems retain USB 2.0 ports for backward compatibility. Linux support: Built-in via the ehci-hcd driver in all…
Grab a release from kernel.org. Recent stable versions (6.x and later) are recommended for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz tar xf linux-6.12.tar.gz cd linux-6.12/ If wget isn’t available, use curl: curl -O https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz Verify the tarball Always verify the kernel’s integrity using checksums and signatures published on kernel.org. This is essential for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz.asc…
The Linux kernel provides the taskstats API to monitor detailed per-task statistics, including I/O wait time, CPU scheduling delays, and memory reclamation waits. Understanding how these metrics are collected at the kernel level is essential for diagnosing performance issues and understanding process behavior. How the Kernel Records I/O Delays The kernel records I/O wait delays…
vimtutor is the most practical way to learn Vim. It’s an interactive lesson built directly into your editor that teaches through practice rather than passive reading. You launch it from the terminal with no setup required, and you get immediate feedback on every command you type. Running vimtutor From any terminal: vimtutor This opens an…
QEMU/KVM uses global locks to synchronize threads, which is necessary for correctness but causes performance problems at scale. When multiple I/O requests and vCPU threads contend for the same lock, you get lock contention that manifests as scheduling jitter, reduced system scalability, and degraded I/O performance. IOThreads (the modern implementation of dataplane) address this by…
CFS (Completely Fair Scheduling) is the default process scheduler in modern Linux kernels. Understanding actual timeslice allocation—how long a process runs before being context-switched out—is essential for performance debugging, verifying fairness assumptions, and identifying scheduling anomalies. The challenge is that /proc interfaces and ps commands show scheduling policy but not the actual on-CPU duration per…
The Completely Fair Scheduler (CFS) is the default process scheduler in Linux kernels since 2.6.23. It allocates CPU time proportionally based on process priority, but the actual timeslices and preemption behavior depend on three key tunable parameters: sched_latency_ns, sched_min_granularity_ns, and sched_wakeup_granularity_ns. Understanding how these work together is essential for tuning scheduler behavior on production systems….
In computer systems, resources must be balanced across available hardware to maximize performance. The Linux kernel runs migration threads as per-CPU daemons to handle this work. These threads manage task migration between CPUs, CPU hotplug operations, and stop-machine synchronization. You can observe migration threads on any modern system: $ ps aux | grep migration root…
CPU affinity binds a process or thread to specific CPU cores, reducing cache misses, improving performance isolation, and managing NUMA locality. The sched_setaffinity() system call is the primary mechanism in Linux. Understanding how it works at the kernel level clarifies scheduler internals and helps you use it effectively. System Call Entry Point The sched_setaffinity() syscall…
RHEL-based distributions only provide 64-bit Wine packages in their standard repositories. Many Windows applications—especially legacy software—require 32-bit Wine. Building Wine from source is the most reliable approach to get a working 32-bit installation alongside 64-bit support. Prerequisites and Resource Requirements Building Wine requires significant resources: ~2GB temporary disk space, ~500MB installed Compilation takes 20-40 minutes…
Systemd replaced traditional init on most modern Linux distributions, shifting terminology from “runlevels” to “targets.” If you’re migrating from older systems, here’s the mapping: Runlevel Systemd Target Purpose 0 poweroff.target Shutdown 1 rescue.target Single-user mode 2, 3, 4 multi-user.target Multi-user, no GUI 5 graphical.target Multi-user with GUI 6 reboot.target Reboot The two targets you’ll use…
Open a terminal and connect to the server: ssh USER@HOST Replace USER with your username and HOST with the server’s hostname or IP address. On first connection, SSH will display the host key fingerprint: The authenticity of host ‘HOST (IP_ADDRESS)’ can’t be established. ECDSA key fingerprint is SHA256:xxxxxxxxxxxx. Are you sure you want to continue…
When you try to unmount a filesystem with umount, Linux may report “device is busy.” This is a safety mechanism — the kernel blocks unmounting when processes or kernel threads are actively accessing the partition or holding open files on it. Forcing an unmount without understanding what’s using the filesystem risks data corruption and data…
When you dock a laptop with an external USB keyboard, the built-in keyboard becomes a nuisance—it’s too easy to brush keys while typing and trigger unwanted input. Rather than disabling the keyboard at the BIOS level or physically disconnecting it, you can use the xinput tool to disable and re-enable it from within your Linux…