Administering Networking OS — Introduction to Linux #1
College Online Material
Evolution of Linux
Linux is the kernel — the central controller. You can add some tools to get an OS
- Shell (enter commands into the system)
- System management (add users)
- Applications (email, web, and development)
Package it up into a linux distribution (distro)
- Debian
- Ubuntu
- Arch Linux
- Fedora
- RedHat
Linux History
Invented as a hobby project in 1991 by Linus Torvalds while at the University of Helsinki in Finland.
People began contributing to making it work on their hardware. The GNU project provided a base set of tools.
What is Unix?
Started in the 1970s at Bell Labs, adopted by universities. Unix is now a trademark of the Open Group.
An OS must be certified to be called UNIX. Linus is not certified so it’s UNIX-like.
Linux Job
- The kernel manages app process
- Allocates and reclaims memory
- Arbitrates access to disk and CPU
- Abstracts hardware-specific functions so app are hardware-agnostic
- Provides security and isolation of users
- Switches between multiple processes (preemptive multitasking)
Open Source
Humans write software in source code and compilers translate sources to machine code.
If you have the source, you can make changes and see how it works. Open sources mean you can inspect and change the source.
Linux Distribution (Distro)
Kernel + Tools + Installation + Package management = distribution
RedHat RHEL
- Fedora, CentOS
Debian
- Ubuntu, MX Linux, RasPi
Linux Runs On…
- Big Iron (e.g. IBM Power System)
- Enterprise servers (Dell, HP, IBM, etc)
- Desktops
- Laptops
- Single board (RasPi)
- Embedded devices/Phones (Android)
Distribution Life Cycle Management
Decision Points
- What will the computer do?
- What software does it need to run?
- Does it need specific hardware or OS?
- Who has to take care of it?
- How long does it need to live for?
Release Cycles
Software and OS upgrades come to a release cycle with updates that can be major or minor.
Example:
- A new version of Fedora is released every 6 months
- Minor releases of RHEL come out every 12–18 months
- Major releases of RHEL come out every 3–6 years
Maintenance Cycles
Software generally goes through phases
- Actively developed
- Bugfixes only
- Security fixes only
- No update
This is the maintenance cycle. A short maintenance cycle means more frequent upgrades are required.
Pros and Cons of Cycles
- Faster releases mean that newer software will be available faster
- Also means you might have to upgrade faster to stay current or will get less stable software
- A longer maintenance cycle means you will be supported at current software levels longer, needing less frequent upgrades
- Longer maintenance cycles often require paid support packages
Software Terms
New features are introduced in Beta versions. Beta is less tested and therefore stable.
After the beta period, the software is promoted to stable. If you need newer features you will often be looking at beta software. Backward compatibility means it still works with the older version.
Comparing OS
Windows
- Split into desktop and server versions
- Slow-release cycle, long maintenance cycle
- Runs a GUI
- Improving scripting
macOS
- Runs on Apple hardware
- The server version adds packages to the desktop version to aid in management and sharing
- UNIX certified
- New major release every 18–24 months
Linux
- Unique in that after choosing Linux you must choose the distribution
- Different distribution focus on different use cases, e.g. desktop, server, scientific, network, etc
- Some dist. offer commercial support, most are volunteer-based
