Linux Tutorial Solved

This tutorial can be complete as long as you have access to a terminal that accepts Linux commands. If you

are working on Linux or Mac this is already installed on your computer and the application is name "terminal".

If you are on Windows some ways you can get access to it are

Installing Cygwin and using the Cygwin Terminal (See the Working Locally Page on Canvas)


Installing WSL


You can also go to the CSIF and complete the tutorial on a computer there.

Linux Tutorial


Common Problems


The CSIF


Logging in Locally


Logging in Remotely


Connect to the School VPN


Choose a Computer


SSHing on MAC


SSHing on Windows


Navigating the UNIX File System


File Permissions


The Remaining Fields


Creating and Deleting Directories


Copying Files


Moving and Renaming Files


Removing Files


Shell Command Line Editing


The Terminate Key


Displaying Files


Logging Out


File Transfer

GUI File Transfer


Learning More About Commands


Submitting Your Assignment


Common Problems

Below is a list of common problems students have encountered while doing this tutorial and how to solve them

If you leave a remote connection to the CSIF idle for too long, it will automatically disconnect you.


You can fix this by closing the terminal you connected to the CSIF and relogging into it.

Forgetting to connect to the school VPN before connecting to the CSIF.


If this happens you will be denied access to the CSIF computer so make sure you are connected to the school VPN first.

Not realizing that you will always be placed into your home directory any time you open a


terminal/connect to the

CSIF

This means that if you are in the middle of the tutorial and say in the directory /usr/home/first/second and you

turn your computer off for the night, the next time you reopen the tutorial you will be in /usr/home and so will

need to use cd to get back to the directory you should be in to continue the tutorial. If you want to reset the tutorial and do it from scratch


    1. Type cd

    2. Type rm -rf first


If the command complains about first not existing, ignore it.


The CSIF

The Computer Science Instructional Facility, CSIF, are computer labs in Kemper 067, 071, and 075 (all in the basement of Kemper) that are available to students to work on assignments for their CS classes.

They come preinstalled with all software that you will need to complete your assignments and serve as a convenient meeting point for partners to get together to work on their assignments in person.

The CSIF uses a networked file system, so it doesn't matter what computer you use. Any work

you do on one computer will appear on all the others. Files are backed up regularly so you are never in danger of losing anything you do there.

Logging in Locally
All students enrolled in a CS course should have an account on the CSIF.

You use your normal UCD username and password to login into a CSIF computer. If you are enrolled in a CS

course but are still unable to log in to a computer contact support over email at support@cs.ucdavis.edu

or in person at 1114 Academic Surge.

To create a terminal window on a PC, click in the upper left corner of the screen.

A search box should appear in the upper middle portion of the screen. Type terminal in the box and select the

application called terminal. A terminal window should now be open. For the rest of

this tutorial will only be typing in one of these terminal windows. If you like you can drag the terminal application to the left side of the screen to add it to your favorites for easier access in the future

Once you have created a terminal window, you will see a “command line prompt” indicating that Unix is ready to accept your instructions. This prompt will usually have your username, computer name, and end with

a "$", but may be terminated by a "%". The prompt is generated by a program known as a shell. This is simply a program that accepts your commands and gets UNIX to execute them.

Logging in Remotely

If you are in the CSIF please SKIP ahead to Navigating the UNIX File System.

Connect to the School VPN

Before you can connect to the CSIF you need to connect to the school VPN. The instructions for how to install

and connect to the CSIF can be found

at https://servicehub.ucdavis.edu/servicehub?id=ucd_kb_article&sysparm_article=KB0006637.

Choose a Computer

Now that you are connected to the school VPN we need to figure out which computer you want to

connect to. A full list of

all the

computers and their statuses can be found

at http://iceman.cs.ucdavis.edu/cgi-bin/nagios3/status.cgi?servicegroup=all&style=overview.

You'll only be able to access this link if you are connected to the school VPN.


You'll want to pick a computer that is whose status UP and preferably and whose services are OK. If a computer's

services are have warnings or criticals it will likely still work but if it doesn't, try a different PC.

The CSIF computers use a networked file system so any files you create on one computer are available on all
computers. So if you find that your favorite computer is down for the day or is just running slow you can connect to a different computer and not lose any work.

SSHing on MAC

    1. Open a terminal. You can find this under Applications/Utilities/Terminal

    2. Type ssh username@pc_computer_name.cs.ucdavis.edu where username is your UC Davis username and computer name

is the name of computer you selected in the previous step (pc13, pc16, pc3, etc).


As an example, if I wanted to connect to pc7 I would type ssh


mfbutner@pc7.cs.ucdavis.edu


    3. If this is your first time connecting to this computer ssh will ask you if you are sure you want to connect.

It looks something like

The authenticity of host 'pc17 (169.237.5.14)' can't be established. RSA key fingerprint is f0:ad:72:d2:2e:84:ab:53:2e:06:60:7d:3e:38:17:3c. Are you sure you want to continue

connecting (yes/no)?

Type yes to confirm that you want to connect.

    4. You will then be prompted to enter your password. Enter it now. When you type nothing will show up.

This is normal and to help protect your password from being stolen by anyone looking at your screen


You should now be connected to the CSIF.

Skip down to Navigating the UNIX File System to continue the tutorial.

SSHing on Windows

You can follow the same steps as listed under SSHing on MAC but open a Cygwin or WSL terminal. Alternatively, you can use the application MobaXTerm which can make things a little easier.

    1. Download MobaXTerm at https://mobaxterm.mobatek.net/download.html. Select the Home Edition

    2. Run MobaXTerm

    3. Click on the Session's drop down menu and select "New session".

The drop down menu, not the one with star

    4. Click SSH

    5. Under "Remote Host" type the pc_name.cs.ucdavis.edu where pc_name is the name of the computer

you selected in the previous step(pc3, pc5, pc16, etc.).

    6. Check "Specify username" and enter your UC Davis username in the box

    7. Click Ok

    8. You will then be prompted to enter your password. Enter it now. When you type nothing will show up.

This is normal and to help protect your password from being stolen by anyone looking at your screen

You'll then be asked if you like to save your password.


If you don't want to have to enter it every time say yes.

You should now be connected to the CSIF.

If you want to connect to the same computer again in the future, you can do so through the sessions button or through the Quick Connect Box on the left.

Navigating the UNIX File System

Each directory in the file system has a path name that uniquely specifies the location of that directory within

the computer’s file structure. As you move within the file structure, you can use the command pwd to display the path name of current location. pwd stands for "print working directory". Type pwd now.


The shell should display /home/ followed by your username, e.g. /home/ssdavis. This is your home directory.

This is the place where you "live" in the Unix file system. Each user has their own home directory that is completely under their control.

The cd (change directory) command allows you to move to any other public directory in the file system. The

syntax for cd is: cd path_name. Now change to the /bin directory by typing cd /bin .


After executing the directory change, use pwd to see that you really are in the /bin directory.


The ls (list) command allows you to see the contents of a directory. The syntax for ls is: ls [-al] [filename] ,

where the "[]" indicate optional values. Now simply type ls .


You will see a list of the names of the files in the /bin directory. The /bin directory holds many of the

basic UNIX

utility programs.
Before you look into the options for ls, I want you back in your home directory. You could type cd /home/

followed by your username, e.g. cd /home/mfbutner, but there is a shortcut. Simply type cd


After the shell has executed the change directory command, type pwd . You can see that simply typing cd without a path name will automatically return you to your home directory.


Now type ls .


If you have not created any files or directories in your account, then nothing will be displayed.

Many shell commands have options that may follow the command after a space and a dash. The options

change the behavior of the command. For ls, the options change what you see giving you specialized types of information which you wouldn't see using the basic command.

Now type: ls –a . The –a option stands for “all”.



You should see a bit more than did you last time. Pay attention to the files that start with a ".".

Files that start with a "." are called hidden files and are not normally displayed as most users don't need to

interact with them.

There are two unusual files listed, ".", and "..".

These have special meanings in path names. "." stands for the current directory.

Now type cd . (with just one period after cd).





Now type 

directory

(the one you were already in)!


"..”" stands for the parent directory of the current directory. Now type cd ..


(with two periods after cd). Now type pwd . You should see “/home”.


Now return to your home directory by simply typing cd


Now type ls –al


The –l option stands for long. The shell will display a line of information for each file. Here is an excerpt from my instructor's directory:

Permissions
Links
Owner
Group
Size
Date
Name







drwxr-xr-x
27
ssdavis
users
4096
Jan 4 21:29
.







Permissions
Links
Owner
Group
Size
Date
Name







drwxr-xr-x
4185
root
users
147456
Jan 7 07:56
..







-rw-r--r--
1
ssdavis
users
1648
Oct 5 1993
.DECkeymaprc







-rw-------
1
ssdavis
users
0
Apr 3 2000
.ICEauthority







-rw-r--r--
1
ssdavis
users
698
Oct 5 1993
.SGIkeymaprc







-rwxr--r--
1
ssdavis
users
2481
Oct 5 1993
.X11Startup







-rw-r--r--
1
ssdavis
users
2285
Feb 26 1997
.addressbook.lu







-rwx------
1
ssdavis
users
2546
Oct 13 10:30
.cshrc







-rw-------
1
ssdavis
users
1869
Sep 25 1996
.cshrc.COPY4U







-rwx------
1
ssdavis
bin
1864
Mar 26 1998
.cshrc.OLD








Your output won't have the headers. I added them so you would know what each field is.

Here is a brief introduction to the information displayed in the long format.

File Permissions

This is the first field in the output.

drwxr-xr-x


The d at the very left says the file is a directory.


The next letters rwx say that the owner (myself) has read, write and execute permissions for the file. For a

directory, execute permission means I can cd to that directory. Read permission means I can use the command

ls to see the contents of the directory. Write permission means I can create additional files in that directory.

The next two groups of three show that other users (group and world) are only allowed read and

execute

permissions.

-rwxr--r--


The dash at the very left indicates an ordinary file, as opposed to a directory. Here the read, write and execute

permissions mean the ability to look at the file (using commands like more, see below), to edit the file (using a

text editor, see below), or execute the file (if it is an executable program -- otherwise this permission

doesn't

mean much).
-rw-r--r--

This set of permissions shows an ordinary file which can only be read and edited by the owner, and only read

by everyone else.

The Remaining Fields

Links: number of shortcuts to this file from other directories.


Owner: who owns this file


Group: what user group this file belongs to


Size: the size of the file in bytes


Date: when the file was last modified


Name: the name of the file


Notice there were no pathnames after any of the ls commands. That means that you saw the contents of the

current working directory. If you do put a pathname afterwards, then you will see the contents of the directory identified by that pathname. Now type ls /


In this example, the pathname you gave ls was the root directory (indicated by a sole backslash), which is

the top directory in the Unix file system. All the files you see listed there are subdirectories of the root. Notice the subdirectory home. That is the subdirectory in which the home directories of everyone having an

account are located.

Creating and Deleting Directories

To create a directory use the mkdir command. Its syntax is mkdir {directory_name}+. The "{}+" indicate that there must be at least one directory name given

Now type mkdir first


Now type ls -l You should have a directory named first now in your file list.


Now type cd first to move into the first directory.



Type pwd to see where you are


Now type mkdir second third


Now type ls –a . The display should be:


. .. second third

The syntax for the remove directory command is rmdir {directory_name}+.

Now type rmdir second to remove the directory named second.



Type ls to check your work.


You should see only third listed.

Copying Files

Use pwd to make sure that you are still in /home/user_name/first.


If you aren't you can type cd ~/first . You can use "~" as shorthand for your home directory.


There are two syntaxes for the copy file command.


    1. cp source_file_name destination_file_name




    2. cp {source_file_name}+ destination_directory

Copy one or more files into destination_directory


But before we can copy a file we need to create one first. Type ls /home > users.txt . This will create

a file named users.txt that has the usernames of everyone on the CSIF.

Now to copy the file type cp users.txt myfile



Use ls to make sure that you were successful. You should see users.txt, myfile, and third listed. Now copy this file down into the third directory by typing cp myfile third

You could check your work by cding into the third directory and then using ls, but there is a simpler way. Just

type ls third to display the contents of the third directory. You should see only myfile listed.


Moving and Renaming Files

The mv command has three syntaxes

    1. mv old_file_name new_file_name, to change the name of a file

    2. mv {filename}+ directory_name, to move file(s) into a directory

    3. mv old_directory_name new_directory_name to change the name of a directory.

You will try each one in order.
Now type mv myfile wombat to rename myfile to wombat.


Use ls to check your work. You should see only third, users.txt, and wombat listed.



Now type mv third/myfile . (note the period indicates the current directory) to move myfile to the current directory.


Again use ls to check your work. You should now have myfile, users.txt, third, and wombat in the current directory.


Now type mv third fourth , to rename the third directory to fourth.


Use ls to check your work. You should now see fourth, myfile, users.txt, and wombat listed.


Removing Files

The syntax of the command to remove files is rm {file_name}+.

Now type rm myfile



Use ls check your work. Your current directory, first,


should now contain only one directory, fourth, and two files, wombat and users.txt.

Shell Command Line Editing

Let’s say you wish to copy wombat into the fourth directory, but you MAKE A MISTAKE type

cp woombat forth/snake , and, BEFORE YOU HIT THE RETURN KEY, you notice your errors. You can go back to make the

appropriate changes by using the left-arrow key to go to the 'o' in forth and the typing u ; then use the left-arrow key

to an 'o' in woombat and hit the Delete key, which will remove the extra 'o'; and then hit the return key to process the command. Try it now.

Type ls fourth to check your work. You should see only snake listed.


On the other hand, if you have already hit the return key when you notice your typing error, you can use the up-arrow to go back to my previous command. Use the up-arrow to go back through several previous

commands, and the down-arrow to go forward. Note that you can also use this to repeat (without change) a previous command.

The shell also allows you to do file name completion, again a great saver of typing and

time. Let’s say you wish to move wombat into the fourth directory. The command would be "mv wombat fourth".
But rather than typing the whole thing, you can type mv w then hit the Tab key. (This is super useful and if

you ever see me typing really "fast" on the command line in examples in class it's because I'm using this.)

Since wombat is the only file in the current directory that starts with 'w', the shell would complete the file name (wombat) for you, you would then just type f and again hit the Tab key.


Since fourth is the only file that begins with an 'f' the shell will complete the file name for your again, giving you "mv wombat fourth/" on the command line!

Hit the then Enter key, and again type ls fourth , and you should see only snake and wombat.


The shell will complete a file name as long as there is only one file with a name that matches what you have

typed so far. This means that you may have to type several letters at the beginning of a file name if there are

other files with identical beginnings of their names. If there are multiple matches you can press Tab twice

to have the shell show you all the files that match what you have typed so far.

The Terminate Key

On the left side of the keyboard is a key labeled Ctrl. Use this key in combination with others to send control

signals to Unix. In UNIX literature, the Ctrl key is specified by using the ^. For example, ^C means "hold down the Ctrl key, then type c". Notice I don't mean capital C, even though by convention that is how it's written. ^C usually causes instant termination of any running program.

For example, the ping utility checks the quality of the network connection between your computer and a remote computer. It will continue to check the quality until you terminate it by typing ^C. The syntax of ping is ping computer_name.

Now type ping pc3 . (If pc3 is down select another comptuer that is up)



Your screen will start filling with lines indicating the quality of the connection to pc3. Terminate ping by typing ^C .


ping should stop, and you should see the command prompt again.

You can use ^C in most situations when a command or program is causing the computer to perform in an

unsatisfactory manner.
Displaying Files

The syntax of the command to display a file is: cat {file_name}+.

Now type cat wombat


This will display the entire contents of the file on the screen. For short files this might be fine, but usually

you will wish to see the file a little at a time.

You can use more {file_name}+ to scroll through a file.


Now type more wombat .


You will see the first screen-worth of the file displayed. To scroll forward one line, press the Enter key. To

scroll forward an entire screen, press the Space bar. To quit in the middle of displaying a file, type the letter

q . There is no way to scroll backwards with more.


Sometimes you will just wish to see the first few lines of a file. You can then use the head command. The

syntax is head [-n] {file_name}+, where "n" is the number of lines to be displayed, e.g. head -3 snake. If you

leave out n, then head defaults to the first 10 lines.

Now type head –4 snake .



You should see the first 4 lines of the file displayed.

Logging Out

If you did not remotely connect to the CSIF please skip this step.


It is time for you to end your ssh session and return to your original computer.

Now type logout


You should receive the message “Connection to pc23 closed.”, where pc23 was the name of the remote

computer you connected to.

You should now see that you are back on your own computer. You can double-check this by running the pwd and ls commands.


File Transfer
You can use the sftp (Secure File Transfer Protocol) command to retrieve or place files in remote locations,

provided you have permission to access the location where the files are.

The syntax of sftp is: sftp computer_name. You are now going to go through the process of getting your wombat file from another computer.

Before doing this step, make sure you are NOT connected to the CSIF through ssh. If you are you will end up transferring file from the CSIF to the CSIF instead of

from the CSIF to your computer. Also make sure you are in directory that you can easily find through your file browser. If you are not, use ls, cd, and pwd to navigate to a directory you can.

Now type sftp user_name@computer_name.cs.ucdavis.edu , where computer_name is some CSIF computer and user_name is

your UCD username name.

You can navigate the remote computer(the CSIF computer) in sftp using the cd, pwd, ls, etc.

If you place an l (the letter L) in front of these commands (lcd, lpwd, lls, etc.) and they will work on your local computer

(the one that is physically in front of you).

Now type pwd , and you will see that you are in your own home directory on the CSIF.



Now type cd first/fourth to move the remote sftp session into the fourth directory.


Now type lpwd . This will show you the directory we will be downloading the files from the CSIF to.


Now type ls to see the files available to you on the remote computer. You should see snake and wombat listed.


The "get" command retrieves files from the remote computer. Now type get snake to download snake to you computer.


Type get wombat to download wombat to your computer.


If you had wanted to move multiple files you could use mget which has the syntax of mget {file_name}+.

So we could have simplified the previous two commands into mget snake wombat.

If you had wanted to transfer a file from the local computer to the remote computer you would use put or mput.

Now that you are done transferring files type bye to end the sftp session.

To check that the files are actually on your computer type ls . You should also be able to see them if you open your file browser to this directory.


GUI File Transfer

There are GUI applications that can help you move files between computers without you

having to type commands. If you are on Windows and using MobaXterm you should see the files on the remote computer on the left side of the screen. If you right-click one you should

see the "Download" option appear. There is also an up-arrow in that area that can be used to upload files to the remote machine.

If you are on Mac, many students in the past have found Cyber Duck helpful for moving files around.

Learning More About Commands

We only cover the most basic of commands in this tutorial along with a few of their options. If you want to learn more about what a command is capable of doing or what comands are available Google is your friend.

Submitting Your Assignment

Find the Linux Tutorial Assignment on Prairie Learn and submit the snake and wombat files you created in this tutorial.