A 2-post collection

Understanding output of free in Ubuntu 16.04

This post explains output of free command in Ubuntu 16.04 paying special attention to information missing in documentation.

Understanding output

Let's look at free output in humanreadable, wide mode:

free -hw

        total   used   free   shared   buffers   cache   available
Mem:     2.0G   566M   860M      14M       41M    531M        1.2G  
Swap:    4.0G     0B   4.0G  

Note that output of free command in Ubuntu 16.04 differs from previous versions.

There are two lines in the output. Mem row shows phisical memory stats. Swap line displays swap stats.

Phisical memory

total: Total installed memory.

used: Cacluclated as total - free -

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Demystifying ifconfig and network interfaces in Linux

This post explains ifconfig output of common developer's box, paying special attention to parameters poorly explained in official documentation. It also slightly touches Linux network interfaces.


ifconfig is a command line tool for UNIX-like systems that allows for diagnosing and configuring network interfaces. At boot time, it sets up network interfaces such as Loopback and Ethernet. Most of the time, however, ifconfig is used for network diagnostics.

Before diving into details of its output, let's first make clear what is an interface.

network interface

A network interface is a software interface to networking hardware. Linux kernel distinguishes between two

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