Outline:

Day 1

• A Brief History of Time...
  • UNIX
  • Free UNIX-like OS's
  • History of GNU/Linux
• The Kernel
• The Other Stuff
• GNU/Linux Distributions
• Installation
  • Sample Dedicated Installation of Red Hat v7.2

Day 2

• Quick System Overview
  • The Boot Sequence
  • Command-Line
  • Graphical
• Comparison to Windows
  • Filesystem Comparison
  • New Software Installation / Maintenance
  • Registry
  • Services
• Security

Related Information

Day 1

A Brief History of Time...

UNIX

UNICS (UNiplexed Information and Computing Service) was created at AT&T Bell Laboratories in the fall of 1969 by Ken Thompson (and a few other researchers) after failed attempts working on the MULTICS project. Their work was the result of trying to create a multi-user, time sharing operating system. They started licensing their code to universities in 1974.

While on sabbatical in 1978, Ken Thompson helped student Bill Joy write the Berkeley Software Distribution (BSD). AT&T's UNIX became a stable commercial product while BSD became a research project and teaching tool. This split between AT&T and BSD remains today. However, most commercial and free UNIXes are a blend of both.

Free UNIX-like OS's

In 1984 and 1985, Richard M. Stallman starts GNU and founds the Free Software Foundation respectively. His goal is to create a totally free (libris) UNIX-like operating system. Though many supporting tools were written quickly, the kernel, called the Hurd, was many years in coming. Also in 1985 Carnegie Mellon creates the MACH kernel based on a micro-kernel architecture.

In 1987 Andrew S. Tanenbaum, a professor in Amsterdam, the Netherlands, creates MINIX as a teaching aid for his Operating Systems class. This was one of the first, complete implementations, of a "free" UNIX-like OS (you had to buy Dr. Tanenbaum's book to get it).

History of GNU/Linux

As part of his schooling at a university in Helsinki, Finland, Linus Torvalds starts writing a new filesystem for MINIX. In 1991, after several disputes with Dr. Tanenbaum, Linus decides to write his own operating system. Over time, with the help of others on the Internet, Linus gets parts of Stallman's GNU software (shells, compilers, etc.) working with his kernel.

From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds)
Newsgroups: comp.os.minix
Subject: What would you like to see most in minix?
Summary: small poll for my new operating system
Message-ID: <1991Aug25.205708.9541@klaava.Helsinki.FI>
Date: 25 Aug 91 20:57:08 GMT
Organization: University of Helsinki

Hello everybody out there using minix -
I'm doing a (free) operating system (just a hobby, won't be big and
professional like gnu) for 386(486) AT clones. This has been brewing
since april, and is starting to get ready. I'd like any feedback on
things people like/dislike in minix, as my OS resembles it somewhat
(same physical layout of the file-system (due to practical reasons)
among other things).
I've currently ported bash(1.08) and gcc(1.40), and things seem to work.
This implies that I'll get something practical within a few months, and
I'd like to know what features most people would want. Any suggestions
are welcome, but I won't promise I'll implement them :-)
Linus (torvalds@kruuna.helsinki.fi)
PS. Yes - it's free of any minix code, and it has a multi-threaded fs.
It is NOT protable (uses 386 task switching etc), and it probably never
will support anything other than AT-harddisks, as that's all I have :-(.

In 1994 he realeased the kernel v1.0 and the associated GNU tools as his first widespread, public, GNU/Linux distribution.

The Kernel

Though he worked hard initially to get the GNU tools working with his kernel, the only code that Linus writes (and controls) today is the kernel. The kernel is at the heart of the operating system. It controls all of the hardware in the machine and provides coordinated access to that hardware. It starts and stops processes (programs), allocates memory to programs, manages virtual memory (swap), associates drivers with hardware, controls interrupts (hardware and software), provides TCP/IP network capabilities, and provides the multi-tasking environment by cycling through all running applications.

Whereas Tanenbaum's MINIX was based on a microkernel architecture that does only a very few things, Linus' kernel is based on a modular, macrokernel architecture where a lot of functionality is built into the kernel. Because the running kernel always has priority over user applications, a macrokernel can improve speed and efficiency of critical operating system functions.

Because of its modularity and open source nature, anybody can add functionality to the kernel. However, Linus has final authority over what is officially added to a kernel release. Kernels are released in "stable" and "development" versions. Stable versions are always even numbered: 2.0.7-3, 2.2.12, and 2.4.9-13 are all stable kernels. Development versions are always odd numbered: 2.1.4, 2.3.5-2, and 2.5.1 are all development kernels. After freezing enhancements and bug fixes to a stable kernel, a new development kernel tree starts. When a development tree becomes stable enough, it gets renumbered as a new stable release.

A final benefit of Linus' open source, modular, macrokernel is the user's ability to remove or include only the parts of the kernel they want or need. This has resulted in full blown router engines, based on GNU/Linux, that fit on a floppy disk. Also, as a system administrator for a server, you can fully optimize the kernel code for what your server does.

The Other Stuff

The only part of GNU/Linux that belongs to Linus is the kernel. Everything else comes from other places. Initially, the majority of the code came from Stallman's GNU project (shells, compilers, tools, etc.) Today, however, there is a large repository of code that, while still open source, isn't licensed under the GPL. Other software is provided under LGPL, BSD, Artistic, Mozilla public, Netscape public, etc. licenses.

GNU/Linux Distributions

In keeping with the idea of Stallman's free software, Linus gave his kernel away for free. Various people and organizations took his kernel, modified it to their needs, selected other open source tools (from the GPL, BSD, etc.), got them working and packaged them all together to release a distribution. Early distributions included (but weren't limited to) Slackware, Yggdrasil, and Debian. The primary distribution in the U.S. today is Red Hat, currently at version 7.2. The primary distribution in Europe today is SuSE, currently at version 7.3. Today's other major distributions include (but aren't limited to) Mandrake (based on Red Hat), YellowDog (for PPCs), Slackware and Debian.

It is important to note that the kernel is completely seperate from any distribution. Kernel development and releases continues on its own schedule. When a new kernel is released, distributions take time to get their configuration and tools working with the new kernel (by adding and removing code to and from the kernel).

Even though most (usually all) of the software in a distribution of software is free (money-wise), distributors still sell GNU/Linux. Purchasing GNU/Linux usually provides you with printed manuals (books), free installtion support, and sometimes commercial software. However, almost every distribution allows you to download a CD ISO image.

Installation

For most distributions, there are several ways to install:
• Boot from floppy and install from CD
• Boot from floppy and install from hard drive (HD)
• Boot from CD and install from CD
• Boot from CD and install from hard drive (HD)
• Boot from floppy and install from the network:
  • NFS
  • HTTP
  • FTP

Sample Dedicated Installation of Red Hat v7.2

The first step is determining which method you will use. For this demonstration, we'll use boot from floppy and install from CD. It should be pointed out that we maintain a Red Hat network installation server on LSU's network. Here are the installation steps:
1. Insert the boot floppy and first CD and boot the system
2. At the boot: prompt, type expert (this gives you more control over the install)
3. After the initial RAM disk image (initrd.img) and kernel (vmlinuz) load off of the floppy you'll get the "Welcome to Red Hat GNU/Linux" screen asking for a driver disk. Unless you have exotic hardware (requiring or that shipped with a driver disk), select "No"
4. For the Installation Process Language, select "English"
5. For the Keyboard Type, select "us"
6. For the Instalation Method, select "Local CDROM"
   Anaconda, Red Hat's install program, will then start and a graphical Red Hat Logo screen will appear
7. For the Mouse Configuration, select your proper mouse type, then check "Emulate 3 Buttons" (Macs use one, Windows uses two, UNIX uses three) then click "Next"
8. Click "Next" to get past the welcome screen
9. Check "Custom" (this give you more control over the install) then click "Next"
10. Check "Manually partition with Disk Druid" (this give you more control over the disk) then click "Next"
11. Delete any existing partitions
12. Create partitions by clicking "New" and enter the following information repeatedly:

    Mount Point	Filesystem Type	Size	Primary Partition
    /boot	ext3	128	Yes
    N/A	swap	256	No
    /	ext3	3072	Yes
    /home	ext3	Fill to maximum allowable size	Yes

    
    When you're done creating paritions, click "Next"
13. For the Boot Loader Configuration, leave "GRUB" selected, leave "Master Boot Record (MBR)" selected then click "Next"
14. For the Boot Loader Password Configuration, leave "Use a GRUB Password" unselected then click "Next"
15. For the Network Configuration, deselect "Configure using DHCP" then enter IP information:

    Label	Value
    IP Address	130.39.198.139
    Netmask	255.255.252.0
    Network	130.39.196.0
    Broadcast	130.39.199.255
    Hostname	emac1.ocs.lsu.edu
    Gateway	130.39.196.1
    Primary DNS	130.39.254.5
    Secondary DNS	130.39.244.30
    Tertiary DNS	130.39.3.5

    
    When you're done entring IP information, click "Next"
16. For the Firewall Configuration, leave "Medium", then check the services you need: SSH, WWW, then for "Other ports" type: dns nfs ntp ssl then click "Next"
17. For the Language Support Selection, leave "English (USA)" selected then click "Next"
18. For the Time Zone Selection, in the "Location" tab, scroll to and select "America/Chicago"
19. For the Time Zone Selection, in the "UTC Offset" tab, scroll to and select "UTC-06 US Central" and check "Use Daylight Saving Time (US only)" then click "Next"
20. For the Account Configuration, you must provide a good, matching password for root (the local administrator of the machine), the click "Add" then enter New User information:

    Label	Value
    User Name	Ron
    Full Name	Ron D. Hay
    Password	work2hard
    Confirm	work2hard

    Then click "OK"

    
    When you're done entring New User information, click "Next"
21. For the Authentication Configuration, leave "Enable MD5 passwords" and "Enable shadow passwords" check then click "Next"
22. For the Package Group Selection, starting with the defaults make the following changes:
    • disable "Dialup Support" (we have no modem)
    • enable "Graphics and Image Manipulation"
    • enable "NFS File Server"
    • enable "Windows File Server"
    • enable "Web Server"
    • enable "Utilities"
    • enable "Software Development"
    • enable "Games and Entertainment"
    
    If you want to, you can check "Select individual packages"
    For Individual Package Selection:
    • open the "Applications" folder, then the "Databases" folder
      • select "mysql"
      • select "mysql-server"
      • select "mysql-client9"
    • open the "Development" folder, then the "Languages" folder
      • select "php-mysql"
      • select "gcc3-c++"
    • open the "System Environment" folder, then the "Shells" folder
      • select "pdksh"
    
    When you're done selecting Individual Packages, click "Next"
23. If the packages you have selected require the installation of dependent packages, you will go to Unresolved Dependencies
    Leave "Install packages to satisfy dependencies" selected, then click "Next"
24. For the Graphical Interface (X) Configuration (because we let X-Windows be installed), leave the default (discovered) selections, then click "Next"
25. For the About to Install, click "Next"
    Sit back, relax, and watch the show! (our install, on a PII 400MHz will take about 20 minutes)
    When the Please insert disc 2 to continue window pops up, switch the CD and click "OK"
26. For the Boot Disk Creation, make sure "Skip boot disk creation" is not checked, insert a blank floppy, then click "Next"
27. For the Monitor Configuration (because we let X-Windows be installed), make sure your proper monitor is selected, then click "Next"
28. For the Customize Graphics Configuration (because we let X-Windows be installed), leave "Color Depth" High Color (16 Bit), leave "Screen Resolution" at 1024x768, change "login type" to Text, then click "Test Setting" to make sure everything works
    After the X-Windows system starts and the Can you see this dialog appears, click "Yes"
    When the Customize Graphics Configuration returns, click "Next"
29. For the Restart System, click "Next"

You're done! Congratulations!

We will shut the machine off during the reboot and continue tomorrow.

Day 2

Quick System Overview

The Boot Sequence

After the BIOS checks the hardware, it reads the Master Boot Record (MBR) from the first Hard Drive (HD) in the machine. Since we installed GRUB (GRand Unified Bootloader), the first thing you see after the BIOS is done is the graphical GRUB screen. GRUB is responsible for loading and transferring control to the operating system kernel. The menu allows you to select which operating system (currently only GNU/Linux) or kernel version (SMP, UP, hand-compiled, etc.) to load. Since our machine only has one processor, we will select the non-smp kernel and press <ENTER>.

GRUB then loads the kernel which immediately starts detecting hardware and loading drivers. As soon as the kernel is fully loaded and initialized (remember, the Linux kernel is a macrokernel architecture that has a lot built into it), it starts init which displays the Welcome to Red Hat Linux message. Newer versions of Red Hat's init allow you to press "I" to enter an interactive mode, letting you selectively choose which services to start (or not start), similar to the Mac when jumping into Extension Manager, or DOS/Windows by pressing F5.

As each service is started, its name is echoed on the left of the screen. If the service starts successfully, a message [  OK  ] appears on the right. If the service failed to start successfully, a message [FAILED] appears on the right.

One of the services that starts is "Kudzu" which provides minimal "Plug-and-Play" functionality. If new hardware is added to a system, Kudzu will (hopefully) detect, configure, and load the appropriate driver for it. Our system has an on board audio chip that Kudzu detects. Chose "Configure" to allow Kudzu to configure and load the appropriate driver. After Kudzu completes, more services will continue to load.

Once all services have loaded (init has finished) the login prompt appears. Since we purposfully selected a Text based login (vs. a Graphical login) we get the default message and prompt.

Command-Line

The command line is the simplest, most fundamental and most common interface for most UNIX-like OSs. Commands in UNIX are typically short (2-4 characters) and usually arcane (i.e. awk, ls). It is beyond the scope of this presentation to teach you all the obfuscation necessary to become a comfortable UNIX user. However, here is a list of the most useful commands:

Command	Description	DOS/Windows Command
cat	Show contents of a file	type
cd	Change directory	cd
cp	Copy a file	copy
echo	Display output	echo
exit	Terminate a session	exit
grep	Find lines in a file	N/A
file	Determine file type	File Extension
find	Find a file	Windows Explorer Find
kill	Terminate a running process	Task Manager
ln	Link a file to another file	Create Shortcut
ls	Display files in a directory	dir
man	Get help about commands	Help
mkdir	Create a directory	mkdir
more	Display a file one page at a time	more
mv	Move or rename a file	rename
passwd	Change user's password	Change Password
ps	List running processes	Task Manager
rm	Remove a file	delete
rmdir	Remove a (empty) directory	rmdir
vi	Edit a file	edit or notepad
wc	Count words, lines and characters in a file	N/A

Graphical

Graphics were not a native part of the original UNIX environment. The X-Windows system, part of the Athena project at MIT, was created to provide a mechanism to display graphics in UNIX. The X-Windows system is only a client / server based protocol for displaying graphics. The system where the graphics are viewed runs an X-Windows server. The system where the graphics are generated runs an X-Windows client. They can be the same machine (as you should be familiar with in the Windows environment), or they can be two different systems an Internet apart.

Most commercial UNIXes provide proprietary X-Windows servers for their version of UNIX. The free UNIX world has concentrated on XFree86 as the primary X-Windows server (in spite of the "86" referring to the Intel x86 architecture, XFree86 has been ported to numerous architectures).

Besides the X-Windows server, the X-Windows protocol requires a window manager to display the windows, however it chooses. The two currently dominant window managers in the free UNIX world are KDE and GNOME. KDE was developed by an independent group of programmers that is a loose approximation of the commercial CDE environment. GNOME development was started, under a free license, by Red Hat but has since moved to another company called Ximian who continues devlopment and provides the free availability.

Running an X-Windows server and window manager on a machine provides a familiar graphical interface. However, both GNOME and KDE require higher amounts of system resources than older, more simpler window managers like fvwm. Luckily, in the free UNIX world the user has a choice (kind of).

Comparison to Windows

The combination of the Linux kernel, GNU (and other) tools, and a modern X-Windows server with GNOME or KDE provides an experience similar to today's Windows systems. Many Windows-like capabilities have been replicated in the modern GNU/Linux/X-Windows environment like desktop icons, file browsing, drag-and-drop, GUI configuration tools, etc.

Filesystem Comparison

UNIX filesystems use a true hierarhical filesystem that starts at a single point: / (pronounced "root" [not to be confused with the root user or /root, the root user's home directory]). Even if several hard disks are in a system, all access to the disks will be through /. This is unlike the Windows world where seperate disks/partitions are accessed via different drive letters (C:, D:, etc.).

The next most difficult thing to grasp about the UNIX filesystem is that everything in UNIX is treated as a file. Several of the "default" directories in GNU/Linux equate to locations in Windows. EVERYTHING! This includes directories, partitions, disk drives, mice, serial ports, printers, displays, network interfaces, etc. Everything.

As mentioned above, everything starts at the "root" (/). This means that all of the devices in a system have a unique path in a UNIX system (i.e. /dev/rmt0 would be a tape drive connected to the system).

Here is a brief table comparing UNIX filesystem locations with their closest Windows equivalents:

Path	Windows Equivalent	Description
/	C:	The start of the filesystem (or main drive in Windows)
/home	My Documents or Profiles or D:	User's private files
/usr or /usr/local	Program Files	Installed software
/dev	Windows or Windows\System	Device drivers
/etc	The Registry or .ini files	Application configuration information
/tmp	Windows\Temp	Temporary system files
/bin	Windows	System executable files

Finally, like Windows, GNU/Linux can access remote filesystems across the network. Windows calls this "Sharing". UNIX calls it NFS (Network File System). Like Windows, which can both share and access Shares, GNU/Linux using NFS can export and mount filesystems. Also, a GNU/Linux system can use Samba to allow Windows machines the ablility to mount part of its filesystem as a Share.

New Software Installation / Maintenance

Modern Windows systems usually install software to a common place: "Program Files". GNU/Linux systems put most software under /usr, either in /usr/bin or /usr/local/bin. The common Windows installer uses "Wise" (or something similar) so that most software installations look and feel the same. Red Hat GNU/Linux uses RPM, the Red Hat Package Manager. Software on Red Hat systems is bundled in a "package." A package includes all of the binary data for the software, rules detailing prerequisite software, and possibly scripts to be executed before, during, and after installation.

Packages come in either source or binary form. Binary packages are architecture specific (i.e. Intel uses i386, i486, i586, and i686; PowerPC uses ppc, SPARC uses sparc, etc.) and can only be installed on the appropriate hardware. The package manger command is rpm which is fully featured. Here is a table of commonly used rpm commands and what they do:

Command	Description
rpm -qa	List all installed packages
rpm -qi package	Show information about an installed package
rpm -qil package	Show information about an installed package including all files in the package
rpm -qip package	Show information about an uninstalled package
rpm -qilp package	Show information about an uninstalled package including all files in the package
rpm -qf file	Determine which installed package a file belongs to
rpm -Uvh package	Install or upgrade a package
rpm -Fvh package	Update an installed package (freshen)
rpm -e package	Uninstall a package
rpm --verify package	Verify the integrity of an installed package
rpm --help	Get help on rpm (there are many more optoins available)

After a Windows installation, the first thing you need to do is update the system. Similarly, after a GNU/Linux OS installation you need to apply new updates. Windows provides a website http://windowsupdate.com/ to obtain updated software. Red Hat provides a website https://www.redhat.com/apps/support/errata/ to do the same. LSU mirrors updates for specific versions of Red Hat at http://redhat.lsu.edu/. Our automated service will also e-mail a user when new updates appear on the mirror. The updates are available over the web at http://redhat.lsu.edu/7.2/updates/ or via NFS at redhat.lsu.edu:/redhat/7.2/updates.

We have already created a document describing the procedure used to update software on a GNU/Linux machine: http://status.lsu.edu/security/linuxmanagement.html#updates and we will use this document to update our newly installed machine.

Registry

While Windows maintains a binary "Registry" to hold system and installed software settings, GNU/Linux puts everything in files. As shown in our table above, the /etc directory tree in GNU/Linux contains most of the files to configure your system and installed software.

For instance, to change the DNS servers on a Windows machine, you have to get to the Network Control Panel applet and navigate through several panels, make the change, and depending on your Windows version, reboot the machine. In Red Hat, all you have to do is edit the /etc/resolv.conf file (you can optionally use the text based tool netconfig or a GUI tool).

Services

Older Windows v9x use the System Tray to emulate "services" running on the system. Windows NT and above actually implement true services which can be controlled using Server Manager. Red Hat controls services via scripts found in /etc/rc.d/init.d/ and automatically starts or stops these services based on entries in the /etc/rc.d/rcx.d/ directories.

For instance, to stop the web server, you simply type:

/etc/rc.d/init.d/httpd stop

To start the web server again, type:

/etc/rc.d/init.d/httpd start

The command ntsysv provides a text menu method of controlling which services start automatically when the machine is rebooted. There is also a nice GUI utility to do the same thing.

Security

The next step in finishing our install of a new Red Hat GNU/Linux system would be securing it. This involves disabling unnecessary services, providing encryption to services that must run, limiting connections to certain IP addresses, presenting banners for running services, securing a service's access to the local filesystem, and implementing a firewall. We have a brief introduction to this process at http://status.lsu.edu/security/intro.html.

Related Information

• The Free UNIX lecture.
• The GNU/Linux lecture.

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The statements and opinions included in these pages are those of Brian D. Ropers-Huilman only. Any statements and opinions included in these pages are not those of Louisiana State University or the LSU Board of Supervisors.
© 1998-2002 Brian D. Ropers-Huilman, Isaac W. Traxler

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