Linux

Btrfs (B-tree file system) is a modern, copy-on-write (CoW) filesystem for Linux designed for high scalability, fault tolerance, and easy administration. It supports advanced features like snapshots, data compression, and built-in RAID. It is widely used in Linux distributions (e.g., Fedora) and enterprise NAS systems for data integrity.

zram: Zram (formerly compcache) is a Linux kernel module that creates a compressed, RAM-based block device, acting as a faster alternative to traditional swap. By compressing data in memory (typically at a 3:1 ratio), it allows systems to store more data in RAM, significantly reducing disk I/O and enhancing responsiveness on low-memory devices.

The Linux kernel includes the Netfilter subsystem, which is used to manipulate or decide the fate of network traffic headed into or through your server. All modern Linux firewall solutions use this system for packet filtering.

The kernel’s packet filtering system would be of little use to administrators without a userspace interface to manage it. This is the purpose of the **iptables** utility: when a packet reaches your server, it will be handed off to the Netfilter subsystem for acceptance, manipulation, or rejection based on the rules supplied to it from the userspace (via iptables). Thus, iptables is all you need to manage your firewall, if you’re familiar with it, but many are available to simplify the task. We’ll take a look at the default frontend used in Ubuntu here.