Exam 1 Unix
The dominant Unix variant today is
. Linux is wildly popular in web servers, smart phones, supercomputers, set-top boxes (Roku-like devices), and home network routers. On the desktop, however, there are many more Apple OS-X (BSD-like) installations than Linux installations.
What is IP address?
An IP address is the Internet Protocol address assigned to each node connected to a network, and to every data packet that the host sends over the network. The data packet's IP address is used to steer the packet to it's destination. There are actually two IP addresses in each packet: the Source Address of the sending host, and the Destination Address of the receiving host.
What is the purpose of the operating system's "Kernel"? The Kernel performs a function. What is the Kernel really? A two-word answer would do nicely.
An operating system's Kernel is a virtual machine in which programs run. It presents the system's physical resources as abstractions to the running programs. The kernel is the primary part of an OS, but its specific function is to execute tasks. Other OS functions (such as supporting a UI) are handled outside the kernel.
Apple's operating system for its Macintosh computers (OS-X) is licensed to use the UNIX trademark
Apple's OS-X, the operating system for the Macintosh, has met The Open Group's trademark certification and has paid the licensing fees to use the UNIX trademark. It's sometimes called "Trademark Unix".
Why was the C language created?
C was created because other languages were either too large (PL/1 and BCPL) to fit on the small machines that Thompson and Ritchie were working with, or inappropriate (FORTRAN) for systems programming. Ritchie used BCPL as the starting point for a smaller language he called B, which he enhanced to New-B, and then to C.
The reason that hidden files are "hidden" is because:
Hidden Files aren't well hidden, so it's not a security or safety feature. It's a convenience feature to keep configuration files from cluttering the home directory when you use ls
The "Unix Wars" almost killed Unix. The "Unix Wars" were competition among Unix vendors triggered by an attempt by AT&T to:
In 1983, the consent decree that forbade AT&T from entering the commercial computing business was lifted, and suddenly Unix became a valuable property. Since AT&T had made investments in Unix, it wanted to reap the rewards, too. It struggled against other companies and especially against UC Berkeley to assert ownership. The resulting commercial upheaval and legal actions were called the Unix Wars.
The inspiration for Unix was this operating system:
Ken Thompson and Dennis Ritchie worked on the Multics operating system project hosted by MIT. Multics provided both positive and negative examples of what an operating system should be, though it provided many more negative examples than positive.
Who originated Linux?
Linus Torvalds started working on Linux, his version of Unix, while a student at the University of Helsinki in Finland. He wanted a complete operating system, but the Unix Wars put BSD under a legal cloud, Unix was too expensive, and Minux was a training system... ...So Toralds wrote his own!
The "Open Source" movement is an ideology that holds that the source-code of all computer programs should be available for anyone to use or modify. This ideology was founded by:
Richard Stallman is a veteran of the MIT Artificial Intelligence Lab, and was mightily rubbed the wrong way by source code treated as a proprietary secret. He started the GNU Project to create a free Unix, founded the Free Software Foundation, and wrote the GNU Manifesto to explain his ideas.
"GPL" means:
The "GPL" is Richard Stallman's "General Public License". It's a legally binding license that guarantees the freedom to run, study, share, and modify the source code of a piece of software.
The program hosts run Sun's Solaris (aka SunOS), and the others (linprog and shell) run Linux.
The CS Department provides two Unix environments: The program hosts are older Sun machines that run an older version of Solaris, a popular commercial Unix. The linprog hosts run Linux, the open-source and most widespread Unix variant today.
Your single Unix login account works with all the Unix hosts that the Computer Science Department provides for students. You don't need a separate account for each one.
The CS Department uses an authentication server that allows you to log into any of several hosts without needing a separate account for each one.
The alternative to Interactive Computing is:
The alternative to Interactive Computing is Batch Processing. Instead of using a terminal to have a two-way dialog with a computer, you submit a job, and come back later to pick up the results. Software development in this environment is very tedious
How do you delete the file named myFile ?
The command to delete a file is rm. The syntax is: rm myFile
How do you make a new directory named myDirectory ?
The command to make a new directory is mkdir. Given that most of the fundamental commands are only two or three letters long, mkdir is surprisingly long: mkdir NewDirectoryName
What does the echo command do? For example: echo "hello world"
The echo command writes a string of text to the screen. For example: echo "Hello World" writes Hello World to the screen. This is surprisingly useful.
ARPA is the federal undertaking that funded much operating system research and development. What event triggered the creation of ARPA?
The effect that the Soviet launch of Sputnik had on the US was profound. ARPA was established as a result, with a mission to guide and fund technological research and development.
It's handy to see a list of everything you typed into the command line. You can get this by using this
The history command lists your past commands. A handy way to view it is to use less as a pager; history | less
The mv command is used to both move a file to a new directory, and to rename a file.
The mv command both moves a file or renames it. Moving and renaming are the same operation; to move a file you really just rename its directory. The syntax is: mv oldFileName newFileName
In the Computer Science Department's systems, which set of hosts is the oldest?
The oldest Unix hosts in the Computer Science Department are the Program hosts. They run a decade-old version of Sun Solaris, the OS created jointly by Sun and AT&T, based on System V, Release 4 (SVR4). The creation of this OS triggered the fragmentation of Unix, which set in motion the Unix Wars.
What command creates an empty file if it doesn't already exist?
The touch command has two functions: touch myFile Makes an empty file named myFile if it doesn't already exist. Updates the time stamp of myFile if it already exists.
Unix has a built in Instruction Manual. To get help about the mkdir command:
There are actually two manuals, man and info. man gives command syntax, info often gives supplementary information. Use them like this: man commandName info commandName
These three commands all display the contents of a text file on the screen, but with different degrees of convenience:
There are three utilities that display the contents of a text file on the screen: more is the original terminal pager that shows the screen a page at a time. less lets you scroll a long file up and down the screen using a more friendly user interface. cat writes the whole file to the screen without stopping; a long file scrolls off the top of the screen.
Unix was created by
Two idle programmers, Ken Thompson and Dennis Richie of AT&T created Unix on an obsolete PDP-7 minicomputer in the aftermath of the disappointing Multics project with MIT and GE. They had help from the other AT&T systems programmers.
How do you preview the files to be affected by a wildcard in a command like rm * ?
Use echo * to show how a wildcard will expand before using it in a destructive command like rm *
How would you jog your memory about how to rename a file when you forget the command?
Use the apropos command to: Find commands that are related to each other. Find a command when you can't remember it's name. apropos searches the Description section of each man page. For example: apropos rename would jog your memory about renaming a file.
There are a number of ways to connect to a remote host. The reason we use SSH for our connections is because it's
We use SSH because it's encrypted and secure. Security ranks above just about every other system characteristic. SSH is an encrypted protocol, hence the name "Secure Shell".
When Unix was passed around to anyone who asked for a copy, it massively caught on in the academic world. The institution that did more than any other to advance the development of Unix was:
While many universities participated in Unix development, it was UC Berkeley that really raced forward with development. They were the ones who integrated it into the early Internet, and distributed their Unix advancements in both free and commercial environments.
You have the same home directory regardless of which CS Unix host you log into.
Your home directory is on a central file server, which connects it to (nearly) every CS host you log into
Navigating Directories using cd : Where does cd .. take you?
cd / takes you to the root directory. cd .. takes you up a directory. cd ~ takes you to your home directory. cd takes you to your home directory, too.
Navigating Directories using cd : Where does cd / take you?
cd / takes you to the root directory. cd .. takes you up a directory. cd ~ takes you to your home directory. cd takes you to your home directory, too.
Navigating Directories using cd : Where does cd ~ take you?
cd / takes you to the root directory. cd .. takes you up a directory. cd ~ takes you to your home directory. cd takes you to your home directory, too.
How do you copy the file named myFile to a new file named myFile.bak ?
cp is the command to copy a file. The syntax is: cp File newFile
To log out of a session, the command is
exit logs you out of your session, as does logout and Ctrl-d
A "pager" displays a long file without scrolling off the top of the screen. Which of these commands provides the most friendly way to view the file myFile ?
less is a sophisticated pager, providing scrolling and search functions. more is an older, less user friendly pager. cat also displays a file, but a long file scrolls off the top of the screen without pausing.
The command to list files in a directory is
ls lists the files in the current directory. The syntax is: ls lists the files in an abbreviated, compact format ls -l lists the files with much more information ls -a lists all files, including hidden ones ls -la combination of the above
The command for changing your password is
passwd is the command to change your password. This command asks you to enter your current password, so if you've forgotten it, you'll have to open a helpdesk ticket to get your password reset.
A full-screen email client for the command line is:
pine is a full-screen email client for the command line, with menus and a full-screen editor.
This command deletes a directory (a folder) even if it contains files
rm -r will delete a directory even if it contains files. "-r" means "remove files/directories recursively" which means to repeatedly descend into the directory and its subdirectories, deleting their contents, until the directory is gone.
This command deletes a directory (a folder) only if it's empty:
rmdir is the safe way to delete a directory (a folder) because it deletes only an empty directory (one with no files).
