CIS 527

Virtualization & Operating Systems

How a Computer Works
Simple Version

• The Operating System runs Software
• The Operating System and software send instructions to the Hardware
• The Hardware performs the operations instructed through electronic circuits
• Data is stored and manipulated physically

Virtualization

• Software that emulates computer hardware
• Run multiple operating systems on a single piece of hardware
• Easily migrate systems between different hardware setups

Types of Virtualization

• Hosted
• Bare Metal (Hypervisor)


• Hardware
• Operating System (Containers)
• Application (Sandboxing)

Old & Busted

• One operating system per server
• One server per application
• Storage per-server
• Lots of servers
• Redundancy is difficult
• Management nightmare

New Hotness

• Many operating systems on a single physical server
• One virtual machine per application
• Shared, virtual storage pools
• Fewer physical servers
• Easy redundancy

Other Virtual Machines

• Oracle VirtualBox
• Hyper-V
• KVM & Qemu
• Parallels
• Virtual PC
• Xen

Cloud Providers

• Digital Ocean
• Azure
• AWS (Amazon Web Services)
• OpenStack
• Rackspace
• Linode

Operating Systems

Image Source: Wikipedia and Wikipedia

Architecture

Image Source: Wikipedia

Kernel

Image Source: Wikipedia

Windows History

• Originally a graphical shell for MS-DOS
• Written in C, C++ and Assembly
• Windows 95 was a huge success
• Windows NT became Windows 2000, XP
• Windows 10 is latest, runs on everything

Windows NT Startup

• BIOS looks in the first sector for a bootloader (NTLDR)
• NTLDR checks for hiberfil.sys. If so, resumes from hibernation
• NTLDR check for boot.ini, displays boot menu to the user
• NTLDR reads uses ntdetect.com to scan for hardware & collect info
• The kernel is loaded, given hardware info, and assumes control

Windows 10 Startup

• Windows Boot Manager is started via EFI
• It reads the Boot Configuration Data (BCD) from disk
• BCD is stored on a special EFI partition in the same file format as the registry
• Using that, it loads winload.exe to load the kernel and device drivers
• The kernel assumes control

Ubuntu History

• Based on the Debian Linux system
• 4.10 - Warty Warthog (Oct. 2004)
• New releases every 6 months
• 14.04 - Trusty Tahr (LTS): 5 years of security updates
• 16.04 - Xenial Xerus due in April

What is Linux?

• A free operating system kernel written to be compatible with Unix
• Most use GNU implementations of core Unix utilities and programs
• Linux Distributions tie a certain kernel to certain programs, utilities, and display managers

Linux History

• 1971 - Unix released by Bell Labs
• 1983 - Richard Stallman creates GNU project to create free Unix utilities
• 1990 - GNU kernel project stalled
• 1991 - Linus Torvalds develops a kernel for use with GNU tools
• 1992 - Linux released under GPL License

Linux History

• 1993 - Slackware & Debian created
• 1994 - Version 1.0 of the kernel
• 1994 - Red Hat & SUSE released
• 1996 - Version 2.0, multiprocessor support
• 1998 - Compaq, IBM, & Oracle support Linux

Major Ubuntu Components

• GNOME Desktop with Unity
• System Settings
• Software Center
• File System Layout
• Configuration Files
• The Dreaded Terminal
• Mir, Wayland, Upstart, Init, etc.

Filesystem Layout

• bin - Binary utilities
• dev - Devices (as files!)
• etc - Configuration files
• home - User files
• lib - Shared libraries
• usr - User Programs
• var - Variable data (logs)

Configuration Files

• Most Linux programs store configuration in text files
• They can be found in /etc
• Usually requires administrator access to edit them
• MAKE BACKUPS! BE CAREFUL!

Other Stuff

• X.org - Library for displaying GUI
• Wayland - Replacing X on most distros
• Mir - Ubuntu's replacement
• init - System startup process
• Upstart - Ubuntu's init replacement
• systemd - New startup process, most distros (incl. Ubuntu) use it now

Ubuntu Boot Process

• BIOS looks for a bootloader in first sector of the disk
• Typically either GRUB or LILO
• The bootloader loads the kernel and the initial ramdisk (initrd)
• The root filesystem is found, mounted, and init/upstart/systemd start loading processes

Ubuntu Boot Process

• The X window system is started
• The desktop environment is loaded (GNOME, KDE, etc.)
• Other services are loaded in parallel
• The system is ready for use

OS Installation

1. Partition the disk
2. Copy installation files
3. Extract & install
4. Configure basic settings
5. Reboot

Next Week

• Command Line Interfaces & Scripts
• Users & Groups
• File System Permissions
• Software
• Security