Knowledge Base

Guides, tutorials, and answers to help you get the most out of Xitoring.

117 articles found

Backup and Restore a GPG Key on Linux

"Back up my GPG key" sounds like one command, but a working restore actually needs four pieces — the public key, the secret key, the ownertrust database, and a revocation certificate. Miss any one and you end up on a new box with keys that exist but don't decrypt, don't sign, or are flagged "unknown trust." This guide walks the full backup-and-restore loop on Linux, with the exact gpg invocations, the right import order, a worked end-to-end example, and the failure modes that surprise people the first time.

linuxgpgbackupsecuritysysadminencryptionkey-managementdisaster-recovery

DevOps & Workflow

Troubleshoot Linux Using dmesg

When something goes wrong on a Linux box — a disk drops, a service gets killed, the network card resets, a process segfaults — the kernel almost always wrote the reason into the ring buffer before anything else noticed. `dmesg` is how you read that buffer. This guide covers how to read it well: the right filters, the right time format, what each common message class actually means (OOM killer, block-layer errors, MCEs, USB resets, segfaults), and the workflow for going from "the box is misbehaving" to "this specific line in dmesg is the root cause."

linuxdmesgtroubleshootingkernelsysadmindebugginglogsobservability

Server Monitoring

How to check running processes on Ubuntu Server

Every Ubuntu Server question that starts with "why is the box slow?" or "what's listening on that port?" ends in the same place — looking at the process table. This guide covers `ps`, `top`, `htop`, `pgrep`, `systemctl`, the `/proc` filesystem, and how to map a noisy process back to the port, file, or service that owns it, with the commands and flags that actually earn their keep on a production server.

ubuntulinuxprocessespstophtopsystemdsysadmintroubleshooting

DevOps & Workflow

How to increase database performance

Most "the database is slow" problems are not the database — they're a missing index, an N+1 from the ORM, a buffer pool sized for last year's data, or a disk that quietly degraded. This guide walks the layers in the order they actually matter: measure first, fix queries and schema, then configuration, then hardware, then architecture.

databaseperformancemysqlpostgresqltuningindexesquery-optimizationsysadmindevops

Server Monitoring

Install & Configure NTP Chrony on CentOS 8

CentOS 8 ships chrony as the only NTP daemon in the base repos — the classic `ntp` package is gone. This guide walks through installing chrony, configuring it as a time server for your network, opening firewalld and SELinux correctly, verifying sync, and monitoring drift on CentOS 8, CentOS Stream 8, RHEL 8, Rocky Linux 8, and AlmaLinux 8.

ntpchronycentoscentos-8rhelrocky-linuxalmalinuxlinuxtimemonitoring

Networking & Diagnostics

Install tcpdump on CentOS 7 and CentOS 8

A focused guide to installing `tcpdump` on CentOS 7 and CentOS 8, including the repository fixes both distros now need (CentOS 8 is EOL and points at vault.centos.org; CentOS 7 reached EOL in June 2024), SELinux and firewalld notes, and a smoke-test capture to confirm it actually works.

tcpdumpcentoscentos7centos8linuxnetworkingtroubleshootingrhel

DevOps & Workflow

Using MySQLTuner to optimize MySQL performance

MySQLTuner is a single-file Perl script that reads your server's status counters and configuration and prints a prioritized list of tuning recommendations. This guide covers installing it, running it safely against a live server, interpreting the output, and — just as importantly — knowing when to ignore its advice.

mysqlmariadbmysqltunerperformancetuningdatabaseinnodbsysadmin

DevOps & Workflow

Optimizing PHP-FPM for better performance

PHP-FPM has more tuning knobs than most people realize, and the defaults shipped by your distro are sized for a generic VPS — not your workload. This guide walks through what FPM actually does, how to measure where it hurts, and which settings — across the process manager, OPcache, the OS, and your web server — genuinely move the needle in 2026.

phpphp-fpmopcacheperformancetuningnginxlinuxsysadmindevops

DevOps & Workflow

Using fdisk to manage partitions on Linux

`fdisk` is the oldest, most widely-installed partition editor on Linux. This guide covers listing disks, creating and deleting partitions, working with GPT versus MBR, writing changes safely, and the modern alternatives (`parted`, `gdisk`, `sfdisk`) you should reach for when `fdisk` is the wrong tool.

fdisklinuxpartitionsdiskstoragesysadmingptmbr

DevOps & Workflow

Add a User to Sudoers in AlmaLinux/Rocky Linux

Granting sudo on AlmaLinux or Rocky Linux is a one-liner — but the right shape of that grant (wheel group vs `/etc/sudoers.d/`, password vs NOPASSWD, all commands vs a narrow list) decides whether the next admin inherits a clean setup or a footgun. This guide walks through every common way to add a user to sudoers on RHEL-derived distros, how to verify the grant works, and how to avoid the classic mistakes that lock you out of the box.

linuxalmalinuxrocky-linuxrhelsudosudoerssecuritysysadmin