Linux & Sysadmin
Red Hat, systemd, networking, storage, performance, firewalls and shell scripting.
Linux & Sysadmin articles
Linux Permissions and ACLs, Properly
Beyond rwxr-xr-x: the special bits, umask, and how POSIX ACLs let you grant one extra user access without changing the group model.
October 24, 2026nmcli: Common Tasks Without the GUI
NetworkManager owns the interfaces on modern RHEL and Ubuntu. Here's the nmcli command for every routine networking change, and the connection/device model behind them.
October 24, 2026systemd Timers vs Cron: When to Use Which
What systemd timers give you that cron doesn't — logging, missed-run catch-up, jitter, resource control — and when plain cron is still the right call.
October 24, 2026Disk Full but df Says There's Space
Five reasons 'No space left on device' happens when df shows free space, and the command that finds each one.
October 24, 2026LVM: Grow a Filesystem Online, Safely
The full chain — grow the disk, grow the partition, pvresize, lvextend, resize2fs/xfs_growfs — with the checks at each step.
October 24, 2026SELinux Without setenforce 0
The five commands that fix 95% of SELinux denials: ausearch, audit2why, setsebool, semanage fcontext + restorecon, and semanage port.
October 24, 2026ss and conntrack for Connection Debugging
ss shows you every socket and its send/receive queues; conntrack shows what the firewall is tracking. Together they explain most 'connection refused' and 'no buffer space' problems.
October 24, 2026Tuning Open File Limits on Linux
Four different limits control how many files a process can open. 'Too many open files' means you're hitting one specific one — here's how to find and raise it.
October 24, 2026How systemd Unit Files Work
A practical walk through writing your first systemd service: the three sections, the dependency model, and how to debug one that won't start.
October 24, 2026auditd Basics
auditd records who did what at the syscall level — file access, config changes, privilege use. Here's how to write useful rules without drowning the disk.
September 16, 2026SSH Server Hardening
The sshd_config settings that matter, in priority order — key-only auth first — plus how to apply them without locking yourself out of the box.
September 16, 2026Finding What Is Using a Port on Linux
The three commands that answer 'address already in use', including the container and namespace cases that trip people up.
September 16, 2026