The GNU Project and free software

In this lab you’ll go looking for GNU on both lab servers: ask each tool who wrote it, find the package it came from, read its licence and compile a tiny program with GCC. Everything is read-only except two package installs and one small folder in your home directory.

Log in to both VMs from your laptop: ssh -p 2211 student@127.0.0.1 for rocky01 and ssh -p 2221 student@127.0.0.1 for ubu01. Your version numbers may be a little newer than the ones shown here if you’ve installed updates.

1Ask the shell who made it

Run this on rocky01:

bash --version

You should see something like this:

GNU bash, version 5.2.26(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Bash is a GNU program, and the second line names the Free Software Foundation as the copyright holder. The licence line says GPLv3 “or later”. On ubu01 the same command shows a newer Bash:

GNU bash, version 5.3.9(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2025 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

The part in brackets is the build target. x86_64-redhat-linux-gnu and x86_64-pc-linux-gnu both end in “linux-gnu”: a Linux kernel with the GNU C library on top.

✅ Checkpoint: You can read the Bash version on both servers and say who holds its copyright.

2Ask ls who wrote it, on rocky01

Run this on rocky01:

ls --version

You should see something like this:

ls (GNU coreutils) 9.5
Copyright (C) 2024 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Richard M. Stallman and David MacKenzie.

Almost every GNU program answers --version and --help the same way, which is one of the GNU coding standards. The last line is a little piece of history: Stallman wrote the first GNU ls himself.

✅ Checkpoint: rocky01 reports ls (GNU coreutils) 9.5 or a newer 9.x.

3Which tools are GNU on Ubuntu 26.04?

Run this on ubu01:

ls --version

You should see this:

ls (uutils coreutils) 0.10.0

That isn’t GNU. Ubuntu 26.04 switched its core utilities to uutils, a Rust rewrite, but kept the GNU versions for the commands where the rewrite still had bugs. Check a handful at once.

Paste this whole block:

for c in ls cat cp mv rm df sort wc chmod; do
  printf "%-6s " "$c"; $c --version | head -n 1
done

You should see something like this:

ls     ls (uutils coreutils) 0.10.0
cat    cat (uutils coreutils) 0.10.0
cp     cp (GNU coreutils) 9.7
mv     mv (GNU coreutils) 9.7
rm     rm (GNU coreutils) 9.7
df     df (GNU coreutils) 9.7
sort   sort (uutils coreutils) 0.10.0
wc     wc (uutils coreutils) 0.10.0
chmod  chmod (uutils coreutils) 0.10.0

On a fresh 26.04 install before updates you may see uutils 0.8.0 instead of 0.10.0. The GNU originals are still there with a gnu prefix, and the normal names are only symbolic links:

gnuls --version | head -n 2
readlink -f /usr/bin/ls /usr/bin/cp

You should see this:

ls (GNU coreutils) 9.7
Packaged by Ubuntu (9.7-3ubuntu2.1)
/usr/lib/cargo/bin/coreutils/ls
/usr/bin/gnucp

✅ Checkpoint: You can name three commands on ubu01 that come from uutils and three that still come from GNU.

4Find the package behind a command

Run this on rocky01:

rpm -qf /usr/bin/ls
rpm -qi coreutils | grep -E '^(Name|Version|License|URL|Summary)'

You should see something like this:

coreutils-9.5-8.el10_2.1.x86_64
Name        : coreutils
Version     : 9.5
License     : GPL-3.0-or-later AND GFDL-1.3-no-invariants-or-later AND LGPL-2.1-or-later AND LGPL-3.0-or-later
URL         : https://www.gnu.org/software/coreutils/
Summary     : A set of basic GNU tools commonly used in shell scripts

rpm -qf answers “which package owns this file?” and rpm -qi prints the package’s details, including its licence in SPDX form (the short standard licence names). On ubu01 the Debian tools do the same job:

dpkg -S /usr/bin/ls
dpkg -l coreutils coreutils-from-uutils gnu-coreutils rust-coreutils | tail -n 6

You should see something like this:

coreutils-from-uutils: /usr/bin/ls
||/ Name                  Version                     Architecture Description
+++-=====================-===========================-============-==========================================
ii  coreutils             9.5-1ubuntu2+0.0.0~ubuntu25 all          coreutils meta package
ii  coreutils-from-uutils 0.0.0~ubuntu25              all          coreutils from the uutils project
ii  gnu-coreutils         9.7-3ubuntu2.1              amd64        GNU core utilities
ii  rust-coreutils        0.10.0-1ubuntu2~26.04.1     amd64        Universal coreutils utils, written in Rust

On Ubuntu, coreutils is now an empty “meta package” that pulls in one provider, coreutils-from-uutils by default. You’ll use rpm and dpkg properly in Lessons 35 and 36.

✅ Checkpoint: You can say which package owns /usr/bin/ls on each server.

5Read the licence that came with the code

Run this on rocky01:

ls /usr/share/licenses/bash /usr/share/licenses/coreutils-common
head -n 2 /usr/share/licenses/bash/COPYING

You should see something like this:

/usr/share/licenses/bash:
COPYING

/usr/share/licenses/coreutils-common:
COPYING
                    GNU GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

RPM packages put licence files under /usr/share/licenses/<package> and other documents under /usr/share/doc/<package>. Debian and Ubuntu keep one machine-readable copyright file per package and the full common licence texts in /usr/share/common-licenses. Run this on ubu01:

grep -m1 '^License:' /usr/share/doc/bash/copyright /usr/share/doc/rust-coreutils/copyright
ls /usr/share/common-licenses

You should see something like this:

/usr/share/doc/bash/copyright:License: GPL-3+
/usr/share/doc/rust-coreutils/copyright:License: MIT
Apache-2.0  CC0-1.0   GFDL-1.3  GPL-2  LGPL-2    MPL-1.1
Artistic    GFDL      GPL       GPL-3  LGPL-2.1  MPL-2.0
BSD         GFDL-1.2  GPL-1     LGPL   LGPL-3

So the shell on ubu01 is copyleft (GPL-3+) and its ls is permissive (MIT). Both are free software, but only the first forces changed versions to stay open.

✅ Checkpoint: You found the licence files for bash on both servers.

6Try GNU long options

Run this on either server:

cd ~
ls -a
ls --all
ls -A
ls --almost-all

You should see something like this:

.  ..  .bash_history  .bash_logout  .bashrc  .cache  .profile
.  ..  .bash_history  .bash_logout  .bashrc  .cache  .profile
.bash_history  .bash_logout  .bashrc  .cache  .profile
.bash_history  .bash_logout  .bashrc  .cache  .profile

Classic Unix gave you short options: one dash and one letter. GNU added long options with two dashes and a readable name, so ls -A and ls --almost-all do the same thing. Long options make scripts easier to read six months later.

GNU programs also accept any unique start of a long option, so ls --alm works too, which leads straight into the first Break-It below.

✅ Checkpoint: You can give the long form of ls -a and ls -A.

7Build a program with GCC and glibc

Install the compiler. On rocky01:

sudo dnf install -y gcc

On ubu01:

sudo apt install -y gcc

Then, on ubu01 (rocky01 works the same way), paste this whole block:

gcc --version | head -n 1
mkdir -p ~/gnu-lab && cd ~/gnu-lab
cat > hello.c <<'EOF'
#include <stdio.h>

int main(void)
{
    printf("Hello from GNU tools\n");
    return 0;
}
EOF
gcc hello.c -o hello
./hello
ldd ./hello
ldd --version | head -n 1

You should see something like this:

gcc (Ubuntu 15.2.0-16ubuntu1) 15.2.0
Hello from GNU tools
	linux-vdso.so.1 (0x00007ffd4b3e2000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f2a6c400000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f2a6c6b1000)
ldd (Ubuntu GLIBC 2.43-2ubuntu2.4) 2.43

GCC turned your C file into a program, and ldd shows it depends on libc.so.6, which is glibc. On rocky01 you get GCC 14.3.1 and glibc 2.39 instead, but the same picture. Nearly every program on the server, from sshd to the package manager, sits on that same library.

✅ Checkpoint: Your hello program prints its line, and ldd shows libc.so.6 on both servers.