Linux
RHEL Basics #6: Filesystem Basics — XFS, mount, /etc/fstab
RHEL 9's default filesystem XFS and how it differs from ext4, viewing disks with lsblk / df / du, the full cycle of partitioning a new disk, formatting with mkfs.xfs, mounting it, registering permanently in /etc/fstab via UUID, and managing swap.
RHEL Basics #5: Users / Groups / Permissions — UID/GID, sudo, ACL
The shape of /etc/passwd and /etc/shadow, the useradd / usermod / groupadd family, what rwx means and chmod's two notations, ACL (getfacl / setfacl) when finer-grained control is needed, and least-privilege sudo — all in one post.
RHEL Basics #4: Intro to systemd — Services, Targets, journalctl
systemd is RHEL's PID 1. Starting and stopping services with systemctl, enabling auto-start on boot, selecting the system's mode via targets, writing your first .service unit by hand, and reading every log in one place with journalctl.
RHEL Basics #3: dnf and Package Management — repo, modules, AppStream
Package management on RHEL is unified under one command: dnf. From everyday commands like install / remove / search / info / history, to why BaseOS and AppStream are split apart, to picking a specific version of a package via modules, to safely attaching external repos like EPEL — all in one post.
RHEL Basics #2: Setup — Installing RHEL 9, Subscription Manager, First Login
Grab the RHEL 9 ISO via Developer Subscription, build a VM in UTM or VirtualBox, walk through the Anaconda installer, register with subscription-manager, and clean up the small post-install items (hostname / time / dnf update / sudo user) — all in one pass.
RHEL Basics #1: What Is RHEL — From Fedora to RHEL, plus AlmaLinux and Rocky Linux
Fedora is where new technology gets tried first; what survives flows into RHEL. CentOS Stream sits in the middle as a preview of the next RHEL, and AlmaLinux and Rocky Linux have settled into the role of free RHEL-compatible distros. Here's the shape of the RHEL ecosystem after CentOS, in one read.
Linux hardware clock time sync
When operating a Linux system, you sometimes need to manually sync the clock because the hardware clock and the OS clock are out of sync. In that case, first check the sync state with the `timedatectl` command.