Deepak Prasad

Compare Ansible command, shell, and raw modules—pipes, argv, creates, removes, changed_when, Python bootstrap, security risks, and when to use dedicated modules instead.

Learn what Ansible is, how agentless automation works, and how control nodes, inventory, modules, playbooks, roles, collections, and vault fit together on Rocky Linux.

Learn Ansible comparison and logical operators, Jinja2 tests such as is defined, and safe when expressions for strings, lists, dictionaries, facts, and registered task results.

Learn YAML syntax for Ansible playbooks—indentation, lists, dictionaries, strings, booleans, multiline values, common mistakes, and ansible-playbook --syntax-check validation.

Learn Ansible facts from the setup module—OS, network, memory, mounts, and Python—plus fact filters, gather_facts control, custom facts.d files, and ansible_local in playbooks and templates.

Learn Ansible ad hoc command syntax with ping, command, shell, package, service, file, copy, user, become, --limit, check mode, troubleshooting, and playbook migration examples.

Learn Ansible roles with a tested demo: directory structure, tasks, handlers, defaults vs vars, variable placement, role dependencies, and when to use roles, include_role, or import_role.

Migrate an already-installed Ubuntu LVM root volume group onto a new LUKS2 physical volume with pvmove, then configure crypttab with initramfs, regenerate the initramfs, and update GRUB for boot-time unlock.

Use systemd-cryptenroll on LUKS2 volumes to add TPM2, FIDO2, PKCS#11, and recovery-key unlock methods, store token metadata in the LUKS2 JSON area, and wire boot unlock through crypttab.

Extend or shrink a LUKS2 ext4 volume on Linux: grow the partition first, run cryptsetup resize on the mapper, then resize2fs; for shrink, reverse the order with offline resize2fs and --size in 512-byte sectors.

Unlock and mount a LUKS USB or moved disk on another Linux host: cryptsetup open by device, UUID=, or /dev/disk/by-uuid, ext4 or LVM inside LUKS, read-only rescue mount, and close the mapper.

Configure LUKS NBDE with Clevis and Tang on RHEL/CentOS: two-VM lab with Tang server, LUKS root client, dracut rebuild, and video—boot without typing a passphrase when Tang is reachable.

Configure crypttab and fstab to unlock and mount a secondary LUKS data partition at boot on Ubuntu or Debian.

Back up and restore a LUKS2 header with cryptsetup luksHeaderBackup and luksHeaderRestore, use a detached header file, and understand when a header copy cannot recover a forgotten passphrase.

Rotate LUKS passphrases and key slots, change cipher or volume key with cryptsetup reencrypt on LUKS2, and back up the header before destructive operations.

Encrypt a new Linux disk partition with LUKS2 using cryptsetup: partition the disk, run luksFormat, open the mapper, create ext4 on /dev/mapper, and mount the volume.

cryptsetup manages LUKS disk encryption through the kernel dm-crypt device mapper. Use it to format partitions, open and close mapper devices, rotate passphrases, back up headers, and inspect LUKS2 metadata on Ubuntu and …

List users in Linux with getent, /etc/passwd, who, and id. Filter normal and system accounts, see logged-in sessions, and check whether a user exists on Ubuntu and RHEL.

Use OpenSSL to view PEM, CRT, CER, chain, bundle, PFX, and P7B certificates. Check expiry, SAN, fingerprint, remote TLS certs, and verify chains.

List groups in Linux with getent, groups, id, and /etc/group. Check user group membership, list group members, and compare primary vs supplementary groups.

Learn how to configure http_proxy, https_proxy and no_proxy environment variables in Linux temporarily, permanently, system-wide, and for tools like curl, wget, apt, git and Docker.

Stop all running Docker containers with docker stop $(docker ps -q), handle empty lists safely, adjust timeouts, force-kill stuck containers, filter by label, and shut down Compose stacks without data loss.

A complete Linux commands cheat sheet with 100+ essential commands and practical examples. Learn file management, system monitoring, networking, permissions, and DevOps-related Linux commands used by administrators, …

Install Node.js on Ubuntu with apt nodejs, NodeSource setup scripts, NVM for multiple versions, or the official nodejs.org linux-x64 tar.xz under /opt, verify with node --version and npm --version, and uninstall per …

Back up a PKCS12 truststore, check the keytool alias and SHA-256 fingerprint, import a CA only when missing, and exit cleanly for Ansible, systemd, and CI pipelines.

Create a code-signing keypair with keytool, sign a sample JAR with jarsigner, verify the signature, and read the PKIX chain warnings jarsigner prints for a self-signed certificate.

Create Java mTLS keystore and truststore files with keytool and OpenSSL, then run a mutual TLS HttpsServer lab that fails without a client cert and succeeds.

Set javax.net.ssl.trustStore and keyStore JVM properties after building a PKCS12 file with keytool: property names, -D flags, JAVA_TOOL_OPTIONS, and a lab that fails without trustStore then succeeds.

Fix PKIX after importing into the wrong cacerts. Find the Java truststore your app actually uses, including bundled JRE cacerts, and import with keytool.

Renew an expired TLS certificate in an existing Java PKCS12 keystore by checking expiry with keytool -list -v, exporting a CSR from the same alias, and importing the CA-signed reply without deleting the private key.