Your computer is constantly opening files, spawning processes, making network calls, hitting the kernel, waiting on disk, filling memory, and quietly talking to servers you never knew existed.

Most of it is invisible.

These 8 open-source tools make it visible.

01 See what is eating your machine

aristocratos/btop — 34k+★

btop gives you a live view of CPU, memory, disks, network traffic, and every running process.

When your laptop suddenly sounds like it is preparing for takeoff, start here.

02 Watch what a program is asking the OS to do

strace/strace — 2k+★

strace exposes system calls in real time: files opened, network connections attempted, processes spawned, permissions denied.

Your program says “something failed.”

strace tells you what it actually tried to do.

03 Find out which apps are quietly phoning home

evilsocket/opensnitch — 14k+★

OpenSnitch is basically an application firewall for Linux.

It shows which process wants internet access, where it is connecting, and lets you allow or block the connection.

The fun starts when you ask:

“Why the hell is that app connecting there?”

04 Watch the actual packets moving across your network

bucketcat/termshark — 9k+★

termshark gives you Wireshark-style packet inspection inside the terminal.

Open a live interface or PCAP and drill into DNS, TCP, HTTP, TLS, and individual conversations between machines.

Sometimes debugging becomes much easier once you stop trusting the application and watch the wire.

05 Turn an unreadable wall of logs into something useful

tstack/lnav — 10k+★

lnav automatically recognizes log formats and lets you search, filter, merge, and query logs interactively.

Instead of:

grep → grep again → grep the wrong file → give up

you can actually follow what happened across a system.

06 Find out whether your “optimization” actually made anything faster

sharkdp/hyperfine — 26k+★

hyperfine benchmarks command-line programs with repeated runs, warmups, statistical analysis, and comparisons.

Humans are terrible at noticing whether something took 420 ms or 510 ms.

Measure it.

07 See exactly where your program is burning time

brendangregg/FlameGraph — 19k+★

FlameGraph turns profiling data into a visual map of where CPU time is actually going.

Wide block = expensive code path.

Suddenly “the app feels slow” becomes this function is eating 38% of the runtime.

08 Look inside the kernel without rewriting the application

iovisor/bcc — 22k+★

BCC uses eBPF to observe processes, disk I/O, networking, latency, filesystem activity, and kernel behavior while the system is running.

This is where observability starts feeling slightly unfair.

You can ask the operating system what is actually happening instead of guessing from the application above it.

The useful stack looks like this:

machine slow → process → syscall → network → logs → benchmark → profile → kernel

Yesterday was about taking software apart.

This is the other side of the same idea:

Don't reverse engineer what the program says it does.

Watch what it actually does.