Sysadmin

In Block-Level Disk Encryption with LUKS, we explored interactive unlocking via passphrases. However, on unattended servers, secondary data drives or database volumes must frequently unlock and mount automatically during system boot without manual console intervention. This guide outlines configuring keyfile-based authentication for LUKS partitions using /etc/crypttab and /etc/fstab. Security Architecture Note: Storing a plaintext decryption key on the same machine that hosts the encrypted data protects against drive theft (decommissioning or drive pulling), but does not protect against complete machine theft where the root filesystem is unencrypted. Ensure your root partition is also protected or store the key on a dedicated hardware token / TPM / networked keyserver. ...

Installing software packages from untrusted third-party repositories poses substantial security risks. In RPM-based systems (RHEL, CentOS, Fedora), an RPM is not merely an archive of binaries—it contains cryptographic signatures, file digests, and embedded shell scripts (“scriptlets”) that execute with full root privileges during installation and removal. Here is how to audit RPM package integrity and inspect scriptlets prior to execution. 1. Auditing Installed GPG Keys When YUM/DNF installs signed packages, it checks them against GPG public keys registered in the local RPM database. ...

In honeypot deployments, captive portals, or specialized traffic inspection environments, administrators often need to forward all incoming traffic—regardless of destination port—to a single listening service (such as an HTTP inspection proxy or logging daemon). This can be accomplished at line rate within the Linux kernel using Netfilter Destination NAT (DNAT) via iptables. Redirecting Inbound Port Ranges via DNAT To redirect all incoming TCP traffic across ports 1 through 65535 arriving on interface eth0 to an internal service listening on port 80 at 192.168.1.10: ...