Ubuntu tutorials

Install Podman on Ubuntu 22.04, 24.04, and 26.04 with apt, check the Podman version your release ships, verify with podman info, test rootless mode, and run a hello-world 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.

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.

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.

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.

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 …

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.

Learn what Terraform state is on Ubuntu — terraform.tfstate purpose, configuration vs real infrastructure, terraform show and state list, drift, sensitive data, Git rules, local vs remote state, and a full local_file …

Learn Terraform providers on Ubuntu — required_providers, provider blocks, aliases, terraform init installation, terraform providers, local and Docker examples, and common provider errors without cloud credentials.

Learn terraform destroy on Ubuntu with the Docker provider — provision disposable resources, preview with plan -destroy, confirm or auto-approve teardown, use -target safely, and understand state and configuration after …

Learn terraform validate on Ubuntu — what it checks, syntax and schema errors with real output, validate -json for automation, init -backend=false for CI, and how validate differs from plan and fmt.

Learn terraform fmt on Ubuntu — rewrite .tf files to canonical style, use -check and -diff, format recursively, enforce formatting in CI, and see how fmt differs from terraform validate.

Learn terraform apply on Ubuntu with the Docker provider — interactive approval, saved plans, -auto-approve, -var and -var-file, in-place updates, -replace, partial failure behavior, and independent resource …

Learn terraform plan on Ubuntu with the Docker provider — read execution plan output, preview create/update/replace/destroy, save plans with -out, and use -var, -destroy, -refresh-only, -detailed-exitcode, -target, and …

Learn what terraform init does on Ubuntu — backend and provider setup, module downloads, .terraform directory, .terraform.lock.hcl, common flags, and when to reinitialize a working directory.

Learn Terraform HCL syntax on Ubuntu — blocks, labels, arguments, expressions, comments, .tf and .tf.json files, multi-file layouts, terraform fmt, validate, and common syntax errors with real fixes.

Prepare a single Ubuntu VM with Docker, helper tools, isolated Terraform working directories, and optional plugin cache so you can practice init, plan, apply, and destroy without cloud credentials.

Install Terraform on Ubuntu 26.04 from the official HashiCorp apt repository, verify with terraform version, install a specific package version or upgrade, install the release binary with checksum verification, and …

Learn what Terraform is and how infrastructure as code works — declarative configuration, providers, resources, state, the init plan apply workflow, realistic use cases, and a local example on Ubuntu without a cloud …