Page 10 - Linux

When top only shows that the CPU is busy but not with what, classic monitoring stops being useful. Kernel tracing with ftrace and perf makes visible which function inside the kernel runs for how long, which syscall is blocking, and exactly where the time in a seemingly simple request disappears to.

An unclean shutdown or a power outage is enough to leave a filesystem with inconsistent metadata. fsck detects and repairs such errors, but only if you follow the workflow, unmounting, checking read-only, and repairing only afterward, in the right order.

The Linux kernel maintains not one but several clocks at the same time, and picking the wrong one for the wrong job leads to bugs that only surface during an NTP correction or a manual time jump. This guide explains the difference between CLOCK_REALTIME and CLOCK_MONOTONIC, why timeouts and retry logic should avoid the wall clock, and how scripts stay robust against time jumps.

An unencrypted backup is a second copy of the most sensitive data in a company, often protected even less than the original. Backup encryption is therefore not a nice-to-have, but a basic requirement as soon as a backup leaves your own server. This article shows how GPG, OpenSSL, restic, and Borg are used on Linux for encrypted backups, and what to watch for in key management.

Classic Linux AIO via libaio generates a separate system call with full context switch overhead for every I/O operation. io_uring replaces this model with two ring buffers shared between kernel and userspace, drastically cutting the number of required system calls, an advantage that becomes especially noticeable in I/O heavy database and search index workloads with high concurrency.

Anyone who spends many hours in the terminal every day feels every small friction immediately: slow prompts, missing autocompletion, unreadable colors, or long commands typed over and over again. Thoughtful terminal customization with a suitable shell, an informative prompt, sensible aliases and a well configured terminal emulator does not save seconds, it saves hours spread across a working week.

Jumbo Frames raise the maximum Ethernet frame size from 1500 to up to 9000 bytes, lowering the percentage of header overhead per transferred megabyte. For the internal connection between a web server and a MySQL database, or for backup and replication traffic, this can noticeably save CPU cycles, provided the MTU is set consistently on every device along the path.

SSH hangs, monitoring no longer reports any values, and the team is unsure whether an immediate hardware reset is the right move. This runbook delivers a clear escalation order for an unresponsive server: from a quick network check, through out-of-band access and Magic SysRq, to a controlled reset as the absolute last resort.

LXC provides true system containers with a full userspace, its own init system and several parallel services, while Docker packages a single application process. For admins looking for a lightweight alternative to virtual machines, the LXD workflow, from installation through networking and storage to snapshots, offers a practical foundation for production environments where a fully-fledged operating system is needed rather than a single process.

Linux capabilities split the traditional root privilege into more than forty individual bits, so a process gets exactly one right, for example binding a privileged port, without inheriting everything else that comes with root. That is the difference between a least privilege design and a server that instantly loses full root access whenever a single compromised service goes wrong.