RHEL family tutorials

Install Podman on Rocky Linux, AlmaLinux, and CentOS Stream with dnf from AppStream, verify with podman info, test rootless mode, run a hello container, and update or uninstall.

Install Podman on RHEL 8, 9, and 10 from AppStream with dnf, compare podman and container-tools, check Quadlet feature gates by version, verify with podman info, test rootless mode, and run a hello container.

Read LeakSanitizer and Valgrind reports down to the line that owns the memory, use the flags that add detail, attribute growth with Massif, and query a running process with vgdb so you fix the cause instead of only …

Diagnose libc.so.6 errors by message type — GLIBC_2.xx not found, cannot open shared object file, wrong ELF class, or damaged system libc — then fix with the matching glibc package, multilib, rebuild, container, or …

Install Fail2ban, enable the sshd jail with sane bantime and ignoreip values, verify bans after failed SSH logins on RHEL and Debian, and unban trusted client addresses when needed.

Fix Vim E325 Found a swap file by the name by reading the .swp prompt, recovering after a crash, or removing a stale swap file once no editor owns it — not Linux swap memory from mkswap.

Diagnose SSH no route to host with TCP port tests, ip route get, remote firewalld and sshd checks, and learn when the message means a firewall REJECT instead of a missing route.

Fix error Failed dependencies when installing a local RPM with dnf install, list requirements with dnf repoquery, install offline RPM bundles, and remove packages safely on RHEL family systems.

Set ClientAliveInterval and ClientAliveCountMax on sshd to drop unresponsive SSH clients, use ServerAliveInterval on the OpenSSH client to keep sessions alive through NAT, and understand how TCPKeepAlive differs.

Install rkhunter from EPEL or apt, update its signature database, baseline file properties with propupd, run a non-interactive check, and interpret warnings in rkhunter.log on RHEL and Debian-family hosts.

Create a custom systemd .service unit under /etc/systemd/system/, explain Unit Service and Install sections, start and enable it with systemctl, and verify with status and journalctl.

Take GNU tar listed-incremental backups with a snapshot file, create level 0 and level 1 archives, inspect Y and N file status, and restore by applying the full backup then each incremental in order.

Reuse one authenticated SSH connection for later ssh, scp, and sftp sessions with ControlMaster, ControlPath, and ControlPersist on the OpenSSH client.

Copy a directory and its contents between Linux hosts with scp -r and rsync -av over SSH, verify the remote layout, and avoid common path mistakes with trailing slashes.

Restrict SFTP users to a chroot directory with OpenSSH ChrootDirectory, ForceCommand internal-sftp, Match blocks in sshd_config, writable upload folders, and SSH public-key authentication.

Configure proxy settings in dnf.conf and yum.repos.d for YUM, DNF 4, and DNF 5 on RHEL-family systems, including authenticated proxies, per-repo overrides, and proxy=_none_.

Set SFTP upload permissions with OpenSSH internal-sftp -u in sshd_config, apply umask per user or group with Match blocks, and understand why umask removes bits but cannot add them.

Set up Apache httpd with TLS, WebDAV, and HTTP basic auth on RHEL-family systems, trust the server certificate on the client with curl --cacert, and upload or download files over verified HTTPS.

Use pkill -P PARENT_PID . to send SIGTERM to every direct child of a parent process, list them with ps --ppid, and clean up script workers with pkill -P $$ . on EXIT.

Enable pam_faillock on RHEL-family Linux with authselect and faillock.conf, verify SSH lockout after failed passwords, and reset tallies with the faillock command.

Install Prometheus from the upstream Linux binary on RHEL-family hosts, add Grafana from the official RPM repository, enable both with systemd, open firewalld ports 9090 and 3000, and connect Grafana to Prometheus on the …

Automate SFTP file transfers in Linux shell scripts using sftp batch mode with SSH keys, or password authentication with sshpass or expect when keys are not available.

Install ARPACK runtime and development packages on Ubuntu, Debian, and RHEL-family Linux from distribution repositories, verify libraries with dpkg or rpm and pkg-config, and link a sample Fortran program against …

Fix “another app is currently holding the yum lock” and modern DNF lock messages on RHEL and Fedora. Find the holding PID, wait safely, and clear stale metadata or RPMDB locks on DNF4 and DNF5.

Add a user to a supplementary group in Linux with usermod -aG, gpasswd -a, or adduser on Debian. Verify with id, apply changes with newgrp or re-login, and avoid the missing -a mistake.

Configure BIND primary and secondary DNS on RHEL-family Linux with allow-transfer, slave zones, named-chroot on Rocky Linux 8, and dig verification after AXFR zone replication.

Learn how to exclude selected users from pam_faillock account lockout on RHEL, Rocky Linux, AlmaLinux, and Oracle Linux using authselect and PAM rules.

Step by step guide to build ceph storage cluster in Openstack CentOS 7 Linux on virtual machine. Confiure OSD, mon using ceph-deploy tool for ceph cluster

Understand kernel-core on RHEL, the difference between kernel, kernel-modules-core and kernel-modules, which packages you need, and how DNF updates them safely.

Update the kernel safely on RHEL with DNF. Check available versions, install the latest kernel, verify the default boot entry, reboot, and confirm the new kernel.