root🐧 Linux & RHEL
RHEL administration, Linux commands, storage, boot, networking and day-to-day troubleshooting.
Guides & references
RHEL Study Guide
Complete Red Hat Enterprise Linux administration reference for RHEL 6, 7, 8 and 9: users, LVM and RAID, SELinux, networking, systemd, NFS, DNS, firewall and more.
Linux Admin Interview Guide
Practical Linux administration commands and real-world Q&As: LVM, SAN and multipath, scripting, networking, security and performance troubleshooting.
Linux Administration Guide
A structured, hands-on Linux administration course: commands, users, systemd, storage, networking, security, performance, backup, patching and scripting.
Fix it: troubleshooting articles
Short, symptom-first pages: quick answer, diagnose, fix, safety notes.
Why Linux says “Read-only file system” and how to fix it
The kernel remounted a filesystem read-only. Learn how to confirm it, find the cause (I/O errors, ext4/XFS errors, SAN/multipath) and recover safely.
Filesystem 100% full: find what is eating the disk
How to find what filled a Linux filesystem: df and du, deleted-but-open files, inode exhaustion, logs and journal, and safe cleanup steps.
High load average: is it CPU, memory or I/O?
A fast triage for high load average on Linux: read uptime, separate CPU, I/O wait and memory pressure, and find the offending process.
systemd service will not start: a step-by-step check
Work out why a systemd service fails: read systemctl status, journalctl, validate configuration, check ports, permissions, SELinux and dependencies.