Linux & Sysadmin
Red Hat, systemd, networking, storage, performance, firewalls and shell scripting.
Linux & Sysadmin articles
The Linux OOM Killer, Explained
When memory runs out, the kernel picks a process and kills it. Here's how it chooses, how to read the aftermath in dmesg, and how to bias or prevent it.
October 24, 2026kdump and Kernel Crash Analysis
When the kernel panics, kdump boots a tiny second kernel to save a memory image. Here's how to set it up, test it, and take a first look at the vmcore.
October 24, 2026fail2ban in Practice
fail2ban tails your logs, matches failed-auth patterns, and bans the source IP for a while. Here's jail.local, writing a filter, and not locking yourself out.
October 24, 2026sysctl Network Tuning for Servers
Most 'network tuning' guides are cargo-culted. Here are the sysctls that actually matter on a busy proxy or app server, with what each fixes and how to check it helped.
October 24, 2026LUKS Full-Disk Encryption
LUKS encrypts a block device with a master key wrapped by up to 8 passphrases/keyfiles. Here's setup, unattended unlock with TPM, key rotation, and header backup.
October 24, 2026Linux Software RAID with mdadm
mdadm gives you RAID 1/5/6/10 in software — flexible, portable, no proprietary controller. Here's array creation, monitoring, and the disk-replacement procedure.
October 24, 2026nftables for iptables Users
nftables replaces iptables/ip6tables/arptables/ebtables with one tool and syntax. Here's the model, a complete server ruleset, and how the concepts map.
October 24, 2026rsync Patterns for Backups and Deploys
rsync's trailing slash, --delete, and --link-dest are the three things people get wrong. Here are copy-paste patterns for snapshot backups and code deploys.
October 24, 2026sudoers Done Safely
A wrong character in /etc/sudoers can lock everyone out or hand out root. Here's the syntax, safe patterns, and the wildcard traps that turn a narrow grant into full root.
October 24, 2026Diagnosing Disk I/O with iostat
%util near 100 doesn't mean the disk is full — it means it's always busy. Here's how to read iostat -x and find which process is hammering the disk.
October 24, 2026firewalld: Zones and Rich Rules
firewalld organises rules into zones by trust level. Here's how zones, services, and rich rules fit together, and the permanent-vs-runtime trap that bites everyone.
October 24, 2026tuned Performance Profiles
tuned bundles dozens of kernel and hardware tweaks into named profiles like throughput-performance or virtual-guest. Here's what it changes and how to make your own.
October 24, 2026