DOS (“Disk Operating System”)

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Lecture 1 - Intro
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Course Overview
Linux BASH
Windows CMD/Powershell
CLI vs GUI
Misc Useful Stuff
Operating System
• Hardware – the physical
components of a system
• Operating System - ???
• Software – the programs we
run
Operating System
• Hardware – the physical
components of a system
• Operating System – What is
this? What does it do?
• Software – the programs we
run
Operating System
• It’s a program
• Essentially, allows users to
run other programs
• More details later!
Operating Systems
• DOS (“Disk Operating System”)*
• Windows: 3.1, 95, 98, NT, ME, XP,
Vista, 7
*Not quite true
Operating Systems
• DOS (“Disk Operating System”)*
• Windows: 3.1, 95, 98, NT, ME, XP,
Vista, 7
• Apple: Snow Leopard
*Not quite true
Operating Systems
• DOS (“Disk Operating System”)*
• Windows 3.1, 95, 98, NT, ME, XP,
Vista, 7
• Apple: Snow Leopard
• Linux: Ubuntu/Kubuntu, Red Hat,
CentOS, Mandriva, etc, etc
*Not quite true
Operating Systems
• DOS (“Disk Operating System”)*
• Windows 3.1, 95, 98, NT, ME, XP,
Vista, 7
• Apple: Snow Leopard, iOS
• Linux: Ubuntu/Kubuntu, Red Hat,
CentOS, Mandriva, etc, etc
*Not quite true
CLI vs GUI
• CLI
– “Command Line Interface”
– Text-based communication with
operating system
• GUI
– “Graphical User Interface”
– Image-based communication
with operating system
CLIs
Is this a CLI?
CLIs
THIS...is a CLI!
CLIs
• Predate GUIs
• Text only
– No mouse!
• Still exist today!
– Why?
CLIs
• Predate GUIs
• Text only
– No mouse!
• Still exist today!
– Still very useful
GUIs
GUIs
• More natural interface
– 2nd generation “point and click”*
• Raster-based feedback
– Images make sense to us
– New desktop managers
removing menu-style interfaces
*See “Samuel Colt”
CLI vs GUI
• What can GUIs do that CLIs
can’t do?
CLI vs GUI
• What can GUIs do that CLIs
can’t do?
– Nothing!
CLI vs GUI
• What can GUIs do that CLIs
can’t do?
– Nothing!
– All of this class can be done
without a GUI.
CLI vs GUI
• What can GUIs do that CLIs
can’t do?
– Nothing!
– All of this class can be done
without a GUI.
– 90%+ of this class should be
done without a GUI.
CLIs
• We will be using:
– BASH
– CMD Powershell
Events
• Modern OSs are event-driven
– Keyboard presses
– Mouse clicks
– BOTH up and down
clicks/presses
Events
• Every event has a timestamp….why?
Events
• Every event has a timestamp….why?
– So we can order our actions
– OS might have a queue built up
– Some events may need delayed
action
– Etc, etc, etc
Events
• Why record events?
– Actions!
• Every time YOU do something,
you probably want the OS to do
something.
Desktop Environments
• Windows
– Various “Windows Explorer”s
• Linux
– KDE, Gnome, etc, etc
• OS-X
– Heck if I know…can probably
run Linux DEs.
– CEG233: Introduction to
Windows and Linux.
Desktop Environments
• GUI interface to the OS
• “Same $#!7, different DE”
– Open folders
– Drag & drop
– Execute programs
– Change system settings
– Cut & paste
– Highlighting
– Etc, etc
Shells
• CLI interface to the OS
– This is the one we care about
• Windows
– CMD, Powershell
• Linux
– cshell, rshell, BASH, etc
Shells
• Windows
– CMD
• “Traditional” shell
– Powershell
• Newer shell
• PS scripting is much closer to
BASH scripting
Shells
• Linux
– sh: Bourne Shell
– ksh: Korn Shell
– rsh: Remote Shell
– csh: C Shell
– bash: Bourne-again Shell
Directory Structure
Dear students,
Please give the bearded man
a moment to draw pretty
pictures. They will help you!
Your Instructor
Picture topics
• Root (of the file system)
– Explicit in Linux
– “Hidden” in Windows
• ‘C drive’ is NOT always the main
drive (mine used to be ‘F drive’)
Picture Topics
• PWD/CWD
– ‘Present’ or ‘Current’ Working
Directory
– “Where am I at (in the tree)?”
Picture Topics
• Absolute paths
– Explicitly state exactly where
the file is
• Earth -> North America -> USA ->
Ohio -> Dayton -> WSU -> Joshi
Center -> JC182
Picture Topics
• Relative paths
– Collectively agree that we’re in
some spot, and go from there
• . -> Joshi Center -> JC182
Picture Topics
• .
– “This” directory
– Used to execute commands in
current directory (coming up
later)
• ..
– Parent directory
Mounting
• We rarely have just one
storage unit
– CDs/DVDs
– More hard drives
– Thumb drives
– Network storage
• In order to access them, we
need to add them to the tree
Windows File System
• C:\Program Files
• C:\Program Files (x86)
– Where user programs are
installed
• C:\Windows
– Where the OS and essential
programs are
Windows File System
• C:\Users & …
• C:\Documents and Settings
– Home Directories
• Your own “private” storage real
estate.
• Each user account has one (by
default)
• They might exist for users that
don’t‘
– Users can get deleted and still leave
their home directory
Linux File System
• /bin
– Contains commands useful to
all users (cat, cd, echo, ls, …)
• /boot
– (Almost) everything needed to
boot the OS
• /dev
– List of all devices on the system
Linux File System
• /etc
– System configuration files
• /home
– Self-explanatory
• /lib
– Contains kernel modules and
libraries needed by commands
in /bin and /sbin
Linux File System
• /media
– “New” mount point
• /mnt
– “Old” mount point
• /opt
– Intended for 3rd party software
• /proc
– Somewhat unique…ignore it
• Virtual file system in its own right
Linux File System
• /root
– Home directory of ‘root’ account
• /sbin
– Commands used for
administration
• /usr
– Contains user binaries, libraries,
header files, help docs, etc
• There’s more in the weeds...
Permissions
• Files
– Read: Can I see the contents?
– Write: Can I change the
contents?
– Execute: Can I run the contents
as a script or program?
• Not applicable to “data” files
Permissions
• Directories
– Read: Can I list the names of
the files in the directory?
• NO FURTHER INFO
– Write: Can I add/remove files
to/from directory
– Execute: Can I list the directory
and related info?
Permissions: UGO
• User
– Who “owns” the file?
• Group
– What collection of folks allowed
to do something with the file
• Other
– If you aren’t one of the above,
you’re this one.
‘ls –l’ Example
drwxr-xr-x 10 admirald7s Installers 4096 2011-10-12 11:33 jdk1.6.0_27
‘ls –l’ Example
d ……………………...-> File type (in this case, a directory)
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Could be ‘-’, ‘d’, ‘c’, ‘l’, ‘b’
rwxr-xr-x ……………-> permissions
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User, then Group, then Others
10 …………………….-> Number of sub-directories and links
admirald7s …………-> user
Installers ……………-> group
4096 ………………..-> Size of directory
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Only things in the immediate directory (not recursive)
2011-10-12 11:33 …..-> Timestamp of last modification
jdk1.6.0_27 …………-> Name of the file/directory
Basic commands
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bash
bg
cat
chmod
chown
cmp
df
diff
du
echo
emacs
env
fg
file
Bourne-Again Shell
background
show each file in sequence
change file permission
change the owner of a file
compare two files
show mounted volumes, etc
show differences between two files
show disk usage
echo/print arguments given
the all-powerful text/binary editor
lists the current environment variables
foreground
guess what kind a file is
Basic Commands
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grep
kill
ln
ls
ltrace
links
ps
set
sftp
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source
ssh
strace
time
print lines matching a pattern
kills a running program
creates a link between two files; try ln –s
list contents of directory; try ls –lisa
show library calls made
WWW/News/Mail browser
shows current processes
set/get the value of shell variables
transfer files securely to/from a remote
machine
execute the commands in a file
remote login securely
show sys calls made
times the following command
Basic Commands
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top
like ps, but with continuous updates
umask
get/set the file mode creation mask
vi
text editor
w
who is on the system
wc
word count, etc
There are more!
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Green are easy commands
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Black are medium commands
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Red are commands that are or can be dangerous is you
don’t know what you’re doing.
Learning Basic
Commands
• NEVER execute unknown
commands
– Research the command first
• Use the man pages
– e.g., “man wc”, “man time”, or
even “man man”
Commands fodder
• Whitespace
– Spaces, tabs, etc
• Tokens
– Not for arcade games
Environmental
Variables
• Variables that help the OS
– PATH
– LD_LIBRARY_PATH
– USERNAME
– TEMP & TMP
– OS
– Etc
• No different than ‘int x = 5;’
PATH
• ‘ls’ is just another
program/script
• When we type ‘ls’, how does
the system know where that
command is?
PATH
• ‘ls’ is just another
program/script
• When we type ‘ls’, how does
the system know where that
command is?
– ‘PATH’ variable
Misc Stuff I Forgot
• File extensions
– Windows uses them to
determine file type
– Linux doesn’t care about them
at all
RVH’s Lab
Disclaimer(s)
1. Labs can be vague
2. This is semi-intentional
3. RVH will give piece-meal
help
4. You WILL have to figure
things out on your own
General Lab
Requirements
• No output, no credit!
• Make it easy to figure out
what text goes with which
step
Lab 2 Pre-Material
• Get a flash drive
– At least 4GB
– Empty (or with contents you
don’t care about)
– If you come with a U3 drive, you
will walk away with a non-U3
drive.
Lab 1 Material
• By ‘use’, I mean ‘use in a
meaningful way’.
• “.bashrc” does NOT exist
on these systems until you
create it.

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