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Linux Master 2· AssociateWeek 1 · Day 5~21 min read

Day 5 - Week 1 Review: The Identity Behind the Name Linux

📌 Key Takeaways

The three layers of kernel / shell / applications and the system calls between them are this week's backbone.
Memorize the lineage in the order Unix (1969) → GNU (1983) → MINIX (1987) → Linux kernel (1991).
For licenses, first split into two branches: copyleft (GPL) or permissive (BSD, MIT).
Tell distribution families apart by the high-level tool — dnf = Red Hat, apt = Debian, zypper = SUSE.
The first exam, "Understanding Linux," has many questions that pair people, years, and names. Memorizing the tables whole is the fastest way.

Lineage Diagram

     1969  Unix           Ken Thompson · Dennis Ritchie (Bell Labs)
       │                  Rewritten in C in 1973 → portability secured
       ├──────────────┬──────────────┐
       ▼              ▼              ▼
   BSD family    System V family   (influenced only)
   FreeBSD          AIX               │
   OpenBSD          HP-UX             │
   macOS            Solaris           │
                                      │
     1983  GNU project   Richard Stallman │  Tools done, kernel (HURD) unfinished
       │                              │
     1987  MINIX        Tanenbaum     │  Educational — inspired Linus
       │                              │
     1991  Linux kernel  Linus Torvalds ◄┘
       │
       └──► GNU + Linux kernel = GNU/Linux → distributions

Pairing People and Years

Person	What they did	Year
Ken Thompson	Developed Unix	1969
Dennis Ritchie	Developed the C language, rewrote Unix	1972~1973
Richard Stallman	Started the GNU project, founded the FSF, wrote the GPL	1983 / 1985 / 1989
Andrew Tanenbaum	Developed MINIX	1987
Linus Torvalds	Developed the Linux kernel	1991

Some questions ask about the order of years rather than just the people. Lined up in a single column, the events look like this.

Year	Event	One-line meaning
1969	Unix development begins	Dropped Multics's complexity, rebuilt small
1973	Unix rewritten in C	Portability secured
1977	BSD distribution begins	Unix splits in two
1983	GNU project begins · System V released	Start of the free software movement
1985	FSF founded	The foundation backing GNU
1987	MINIX announced	An educational microkernel OS
1989	GPL released	The legal device of copyleft
1991	Linux kernel 0.01 released	The kernel GNU lacked appears
1992	Linux kernel adopts the GPL	Trigger for worldwide developer participation
1994	Linux kernel 1.0	The first official version
1998	OSI founded	The term 'open source' appears

GNU (1983) comes before the Linux kernel (1991). Order-flipping options like "after Linux came out, GNU built the tools" are common.
The FSF (1985) and OSI (1998) are 13 years apart. Free software came first, open source later.

Kernel and Linux Features

What's asked	Answer
The kernel's five big jobs	Managing processes · memory · file system · devices · network
The channel applications use to make requests to the kernel	System call
Structure of the Linux kernel	Monolithic + loadable modules (LKM)
List / load / unload modules	`lsmod` / `modprobe` / `rmmod`
The property of many people using it at once	Multi-user
The property of running many programs at once	Multi-tasking
Multiple login screens on one monitor	Virtual console
Borrowing disk when memory runs short	Virtual memory (swap)

Unix Philosophy and Standards

Philosophy: small programs · connected to each other (pipes) · text as the common language · everything is a file.
Tell standards apart by "who is trying to align what."

Standard	One line
POSIX	The interface standard for Unix-family systems made by the IEEE
SUS	The trademark certification criteria for "UNIX" (The Open Group)
LSB	A compatibility standard among Linux distributions
FHS	The directory structure standard

Contrasting Confusing Pairs

Category	A	B	Distinguishing criterion
Kernel vs shell	Kernel — hardware control	Shell — command interpretation	Does it touch hardware directly?
Monolithic vs microkernel	Linux, Unix	MINIX, Mach	Are all the functions inside the kernel?
BSD vs System V	FreeBSD, macOS	AIX, HP-UX, Solaris	Berkeley or AT&T?
Free software vs open source	FSF, emphasizes ethics	OSI, emphasizes practicality	Emphasis (the code lists are nearly the same)
Copyleft vs permissive	GPL, LGPL, AGPL	BSD, MIT, Apache	Must derived works be released too?
GPL vs LGPL	Release even if linked	Exempt if only linking	Is there a library exception?
RPM vs DEB	Red Hat and SUSE	Debian and Ubuntu	Format alone is not enough → use the high-level tool
Fedora vs RHEL	Testing ground, short cycle	Commercial, long-term support	Before or after validation?

Looking at Licenses and Distributions Together

Licenses can be lined up by a single question: "Must you release the source when you modify and distribute?"

Strength	License	Scope of release
Strongest	AGPL	Release even if you only offer a network service without distributing
Strong	GPL	If you distribute, release the entire combined work
Weak	LGPL	Only the parts of the library you modified. Your own code that links to it is exempt
Weak	MPL	Only the modified files
None	BSD · MIT · Apache	No release obligation. Only the copyright notice (Apache includes a patent clause)

Also sort out the names divided by price and source availability — freeware (free, closed source) / shareware (paid after a trial) / public domain (no copyright) / free and open source (source published, license terms followed).

For distributions, recall in the order family → format → tool → members.

Family	Format	Low-level · high-level	Members
Red Hat	`.rpm`	`rpm` · `yum`/`dnf`	Fedora, RHEL, CentOS, Rocky, Alma
Debian	`.deb`	`dpkg` · `apt`	Debian, Ubuntu, Mint, Kali
SUSE	`.rpm`	`rpm` · `zypper`	SLES, openSUSE (`YaST`)
Others	Each its own	`pacman` / `emerge` / `pkgtool`	Arch / Gentoo / Slackware

The flow in one line: Fedora → CentOS Stream → RHEL → Rocky·Alma, Debian → Ubuntu → Mint.

Practice Judging Answer Choices

The exam demands the ability to tell whether a single sentence is right or wrong. Read the sentence below, judge it yourself first, then check the right-hand side.

Statement	Verdict	Reason
The shell controls hardware directly	✗	Control is the kernel; the shell only interprets
The Linux kernel is a microkernel structure	✗	It is monolithic. The microkernel is MINIX
Unix was written in the C language from the start	✗	It started in assembly and was rewritten in C in 1973
The C language was created by Dennis Ritchie	○	Beware of confusion with Ken Thompson
The GNU project failed to complete a kernel	○	HURD was delayed
Solaris is BSD family	✗	It's System V family
GPL software cannot be sold for money	✗	It can be sold. You just have to give the source
Freeware is a kind of free software	✗	It's only gratis, without the freedom to modify or redistribute
A program that only links an LGPL library doesn't have to release its source	○	The library exception
openSUSE uses RPM packages	○	Still, it's not the Red Hat family
Fedora is a distribution that rebuilds RHEL	✗	The order is reversed. The rebuilds are Rocky·Alma
You can learn the distribution name with `uname -r`	✗	It shows only the kernel version. Look at `/etc/os-release`

Commonly Mistaken Points

"Free software = gratis" → No. Selling it for a fee is possible. Freedom is about rights, not price.
"If it's RPM, it's Red Hat" → SUSE uses RPM too. You must tell by looking at zypper.
"Linux is a kind of Unix" → It didn't inherit the code. It is Unix-like, modeled only on the behavior.
"GNU made Linux" → GNU made the tools and Linus made the kernel. The two were combined.
"Even kernel version = stable" → An old rule from before 2.6. It's irrelevant now, but it still appears on the exam.
"Android is a Linux distribution" → It shares only the kernel and doesn't use the GNU tools.

Command Summary

Command	What it does
`uname -a`	Everything: kernel name, version, architecture
`uname -r`	Kernel version only
`cat /proc/version`	Detailed information the kernel reports
`echo $SHELL`	The current login shell
`cat /etc/*-release`	Distribution name and version

Next week is about actually installing this operating system — we cover installation types, partitions, file systems, and boot managers.

📖 Glossary

Unix-like : An operating system that didn't inherit Unix's code but whose behavior and command system resemble Unix.
Portability : The property of making something run on other platforms without major changes. The reason Unix was rewritten in C.
Loadable kernel module (LKM) : A piece of functionality that can be attached to and detached from the kernel while it runs.
Viral : The property that a work using GPL code must also be released under the GPL.
Fixed release : A distribution model that issues new versions on a set cycle.
Rolling release : A distribution model that updates continuously with no version divisions.

📝 Practice Questions

Click a choice to reveal the answer and explanation.

Question 1

Which of the following correctly pairs the person who first developed the Linux kernel with the year?

Question 2

Which of the following best describes the relationship between Linux and Unix?

Question 3

Which of the following most accurately describes the relationship between the GNU project and the Linux kernel?

Question 4

Which of the following groups consists only of copyleft-type licenses?

Question 5

Which of the following pairings of a distribution and its family is NOT correct?

Question 6

Which of the following is the best way to check the name and version of the distribution installed on the current system?

Official references

Linux Master 2 official exam syllabus(opens in a new tab)