Page 14 - Linux

The disk I/O scheduler on Linux decides in what order read and write requests get passed to the block device, long before MySQL itself notices anything. On NVMe storage, the wrong choice can cost more latency than any MySQL configuration change could ever save.

gum and whiptail turn a Bash script into an application with real borders, forms and confirmation dialogs, without needing a graphical interface. This article shows how to use both tools in your own scripts, where they differ, and when the effort pays off compared to plain Bash built-ins.

Namespaces isolate what a process can see, seccomp limits what a process is allowed to do at all. Anyone thinking about container hardening purely in terms of capabilities and namespaces overlooks one of the most effective defenses against kernel exploits: deliberately blocking system calls an application simply never needs during normal operation.

A single process permanently consumes 100 percent CPU, but nobody knows why, there was no deploy and no configuration change. This article walks through the complete diagnostic path for mysterious CPU usage: from the first suspicion in top, through thread analysis and syscall tracing with strace, to the exact code path with perf.

Anyone who starts long running processes on a remote server while relying on a plain SSH terminal risks losing all progress the moment the connection drops. tmux and GNU Screen solve this by decoupling sessions from the actual terminal and keeping them running in the background, whether the connection wobbles or the laptop lid closes.

Every Linux process carries a unique PID and points to its parent via its PPID, which naturally forms a traceable tree of parent and child processes. This article shows how to read that tree with ps and pstree, why orphaned processes get reparented to PID 1, and how to track down and terminate a hung PHP-FPM worker in practice.

Anyone who treats kernel modules as a black box is missing one of the most useful diagnostic tools on Linux. lsmod, modinfo and modprobe show which drivers and subsystems are actually loaded, how dependencies between modules get resolved, and how to load, remove or permanently block a module without ever recompiling the kernel.

A stolen server or a removed disk is an open book without encryption. LUKS encrypts entire block devices transparently for the filesystem on top and can even be unlocked automatically with keyfiles, without sacrificing protection against physical theft.

chroot is one of the oldest isolation tools on Unix and, at the same time, one of the most misunderstood. Anyone building a jail environment to seal off a process from the rest of the filesystem must understand exactly what chroot actually secures and where that protection ends, since many servers have already been compromised through a chroot environment mistakenly believed to be secure.

An environment variable that works fine in the administrator's shell but is simply missing inside the PHP-FPM process of a Magento application is one of the most common puzzles in daily server operations. The reason is almost always scope: environment variables are only inherited by child processes, never backward and never across independent process trees, and system wide scope works fundamentally differently from user specific scope.