Changes

:* Understand the importance of how digital computers store data (i.e. data representation)

:* Perform various Manually perform '''numbering conversions''' between the '''decimal''', '''binary''', '''octal''' and '''hexadecimal''' numbering systems<br>by hand (<u>without</u> the use of a computer or calculator)

:* Identify Explain the purpose of '''which numbering system conversion method to usefile permissions''' when required to perform a numbering conversion

:* Understand directory and regular file Explain how permissions work differently for '''directories''' as opposed for '''permissionsregular files'''

:* Learn how to '''set''' directory and regular Change file '''permissions''' with the '''chmod''' command (both ''symbolic '' and octal ''absolute'' methods)

:* Learn how to use Use the '''umask''' command to have automatically assign permissions for '''newly created directories ''' and files automatically set upon their '''creationregular files'''<br><br>

|colspan="1" width="22%" |'''Slides:'''<ul><li>Week 4 Lecture 1 Notes:<br> [https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-4.1.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murrayuli101/slides/ULI101-4.1.pptx PPTX]</li><li>Week 4 Lecture 2 Notes:<br> [https://wiki.cdot.senecacollege.saulca/uli101/slides/ULI101-Week44.2.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101slides/ULI101-Week44.2.pptx PPTX]<br></li></ul>

| style="padding-left:15px;" | '''Data Representation Definitions:'''

| style="padding-left:15px;"|'''File Permission Concepts:'''

'''File Permission Commands:'''<br>* [httphttps://man7ss64.org/linux/man-pagescom/man1bash/chmod.1.html chmod]<br>* [httphttps://man7ss64.orgcom/linux/man-pages/man1bash/umask.1p.html umask]<br><br>

|colspan="1" style="padding-left:15px;" width="30%"|'''Instructional Videos:'''* [https://www.youtube.com/watch?v=L2zsmYaI5ww 4nGgqLIKU9U Numbering Conversions]

===Why Study Data Representation?===[[Image:binary-number1.png|right|200px|https://creativecommons.org/licenses/by-sa/3.0/ cc]]Digital computers are '''electronic devices''' that contain a series of '''circuits''' and voltage levels that can store / represent data.

<table align="right"><tr valign="top"><td>[[Image:binary-number1.png|thumb|right|220px|A series of '''binary Binary numbers''' form a '''byte''' to can represent '''numbers'''those series of circuits with voltage levels.<br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]</td><td>[[Image:Those binary-number-2.png|thumb|right|200px|'''Bytes''' can be used numbers are combined in a sequence to also represent form a '''charactersbyte'''. It is job of a program to know if bytes Bytes are used to represent numbers or charactersrepresent numbers or characters. Learning to convert numbering systems<br>(like '''Hexadecimal to Binary''') can be used to know how a character is represented in '''binary'''. <br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]</td></tr></table>''Data ... is any sequence of one or more symbols given meaning by specific act(s) of interpretation.Digital data is data that is represented using the binary number system of ones (1) and zeros (0)...''<br>Reference: https://en.wikipedia.org/wiki/Data_(computing)<br><br>

IT professionals may need to perform '''numbering conversion'''Reasons to Understand Data Representation:use with<br>''programming functions'' or ''OS commands'' to perform common operations on a computer system.

* ''C ProgrammingIT Professionals that Use Data Representation:'' Sending information over networks, files* ''Web Development:'' Setting color codes for webpage background or text * ''Allowing or Limiting Unix / Linux File Access:'' Setting ''permissions'' for files and directories

 In this tutorial, you will learn how a simple decimal number (integer) is stored into the computer system as a binary number. We will also learn other numbering systems (octal and hexadecimal) that can be used as a "short-cut" to represent binary numbers.<br><br> ===Decimal / Binary / Octal / Hexadecimal Numbering Systems=== [[Image:decimal-number-3.png|thumb|right|300px|The '* ''decimalNetwork Specialists''' numbering system .<br>(Image licensed under [https://creativecommons.org/licenses/byBuilding Large Networks via Sub-sa/3.0/ cc] - modified by author).]]netting* ''Decimal Numbers'' The '''decimal''' numbering system consists of digits consisting of numbers '''0''' to '''9'''. The fact that humans started counting on their fingers and thumbs most likely lead to the development of this numbering system. The numbering system is based on sums of the power of 10 which provides rules for mathematic calculations. Referring to the diagram to the right, the value of each decimal digit consists of the value (placeholder) multiplied by the corresponding power of 10. For example, '''units''' are '''10⁰''', '''tens''' are '''10¹'Programmers:''Sending information over networks, '''hundred''' are '''10²''' which move in a '''right-to-left''' direction.files<br><br>[[Image:binary-number-3.png|thumb|right|200px|The * '''binary''' numbering system.<br>(Image licensed under [httpsWeb Developers://creativecommons.org/licenses/by-sa/3.0/ cc])]]''Binary Numbers'' The '''binary''' numbering system consists of digits consisting of numbers '''0''' Setting color codes for webpage background or '''1'''. Digital computers have circuits which representing data in terms of voltage levels. Multiple circuits are used to represent data (in the form of ''binary'' numbers). The numbering system is based on sums of the power of '''2'''. Referring to the diagram to the right, the value of each decimal digit consists of the value (placeholder) multiplied by the corresponding power of 2. For example, '''2⁰''' , text '''2¹''', '''2²''', etc. which move in a '''right-to-left''' direction.<br><br>* ''Octal Unix/ Hexadecimal Numbers''<table align="right"><tr valign="top"><td>[[ImageLinux System Administrators:octal-number-2.png|thumb|right|200px|The ''Setting 'octal'permissions'' numbering system.<br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]</td><td>[[Image:hex-number-2.png|thumb|right|420px|The '''hexadecimal''' numbering system.<br>(Image licensed under [https://creativecommons.org/licenses/by-sa/3.0/ cc])]]</td></tr></table>The '''octal''' and '''hexadecimal''' numbering systems consist of digits of numbers '''0 to 7''' and '''0 to F''' respectively. For ''hexadecimal'' numbers, values for '''10 to 15''' are represented by the characters '''A to F''' respectively. The '''octal''' files and '''hexadecimal''' numbering system are based on sums of the power of '''8''' and '''16''' respectively.directories <br><br>

 ====<u>Method 1: Binary to Decimal</u>====

# Write down the binary number.<br># Starting from the '''right-side''', draw '''L''''s below the binary number moving to the left <br>(refer to diagram on right).<br># Starting on the right''rightmost'' "'''L'''", multiply the number value (placeholder) by '''2''' to the power of zero.<br># Repeat Continually repeat '''step #3''' moving to the leftleftwards, but increase increasing the power of ''2'' by '''1 each time'''<br>(refer to diagram on right).<br># Add up the results to obtain the decimal value equivalent.<br><br><br>'''NOTE: ''' To convert other numbering system ''octal'' and ''hexadecimal'' numbers to '''decimal''', replace the number <span style="color:red;font-weight:bold">2</span> <br>(in red in the diagram to the right) with <span style="color:red;font-weight:bold">8</span> (for ''octal'') or <span style="color:red;font-weight:bold">16</span> (for ''hexadecimal)''').

==== <u>Method 2: Decimal to Binary </u> ====

# On the left side, write Write down the '''decimal number''' to be converted.# Far to On the ''right-side'', write the number '''number 1''' and while moving '''leftwards''', '''double keep <u>doubling</u> the numbers until that numberis ''' until that number is NOT greater than ''' the decimal number to be converted (refer to the diagramon the right).<br># If you are converting to 8Starting on the left-bitside of those doubled numbers, 32-bit, etccompare that number with the decimal number.If that number if less than or equal to the decimal number, enter then write a '''leading zeros1''' if those doubled numbers are below and subtract that number from the decimal number to get a remainder. If the number is greater than decimal number (or remainder), then write a '''greater than0''' the decimal numberbelow.<br><br># Moving in a Repeat '''rightwardsstep #3''' direction, if (moving rightwards and comparing the doubled number with the decimal's remainder)<br><br>''less'NOTE:'' than the decimal number, write a 'If you are converting to ''1'8-bit'' and subtract the double number's value from the decimal number.<br># If the next doubled number is , '''greater32-bit''' then the remainder, then write a etc., add '''zeroleading zeros'''; otherwise, if the number is less than but not zero, repeat the above steps #4 and #5 until you have obtained your binary numbernecessary.<br><br><br>

==== <u>Method 3: Octal to Binary / Binary to Octal </u> ====

# Multiply the placeholders value or "placeholder" (i.e. '''0''''s and '''1''''s) by the corresponding '''(4)(2)(1)''' for each group to obtain the octal number (refer to diagram of ''binary to octal'' conversion).<br><br>

==== <u>Method 4: Hexadecimal to Binary / Binary to Hexadecimal </u> ====

# Write '''(8)(4)(2)(1)''' under <u>each</u> group of 3 4 binary numbers.# Multiply the values or "placeholders " (i.e. '''0''''s and '''1''''s) by the corresponding (8)(4)(2)(1) for each group to obtain the octal number.

===File Permissions= <u>Method 5: Octal to Hexadecimal / Hexadecimal to Octal</u> ====

Since the Unix / Linux operating systems allow for ''Example:'multiple users''' to be created on a single server,<br>it is essential for users on these servers to '''share''' or '''limit''' access to directories and files contained in those directories.

[[Image:listing-file-directoryTo convert octal to hexadecimal, convert octal to binary, then convert binary to hexadecimal.png|thumb|right|400px|Detailed directory listing showing permissions for a '''directory''' and a '''regular file'''.]]

When '''directories''' and r'''egular files''' are created, they are assigned to an '''owner'''<br>(typically the username which is the creator).To ''allow'' or ''limit'' '''access''' convert hexadecimal to those files and directoriesoctal, those files and directories are assigned convert hexadecimal to an initial '''group''' referred binary, then convert binary to as a "'''primary group'''"octal.<br><br>

'''NOTE:''' In this course, we cannot create groups or assign users to groups - you may learn how to do<Br>that if you take a Unix/Linux administration account.On the other hand, you can change which '''user''',<br>existing '''same group members''' or existing '''other group members''' can or cannot access a directory or regular file.<br><br><table align="right"><tr><td>[[Image:listing-file-directory-permissions.png|thumb|right|350px400px|Permissions of Detailed directory listing showing permissions for a '''directory''' that contain subdirectories and regular files.]]</tdbr><td>[[Image:file-permissions.png|thumb|right|350px|Permissions of and a '''regular file''' contained within a directory.]]<Since Unix /td></tr></table>File Permissions consist of Linux operating file systems allow for '''two-layersmultiple user accounts''':<br><br>''First'', the permissions of it is essential to have a system to '''directoryshare''' that contains regular files, and or ''second'limit', permissions of the '''regular access to directories and files''' themselvescontained within the file system.

When ''Permissions for Directory 'directories''' and r'''egular files''' are created, they are assigned to an '''owner'''<br>(typically the username which is the creator).To ''allow'' or ''limit'' '''access''' to those<br>files and directories, those files have and directories are assigned to an<br>initial '''group''' referred to as a different meaning than "'''primary group'''".[[Image:directory-permissions for .png|thumb|right|350px|Permissions of a '''directory''' that contain subdirectories and regular files.]]Users that <u>own</u> those ''directories'' and ''regular files:''are referred to as '''users''', users that belong within the <u>same group</u> are referred to as '''same group members''', and those users that do <u>NOT</u> belong to a particular group are referred to as '''other group members'''.

:*Referring to the <u>rightmost</u> diagram above, '''read''' (''Permissions for directories have a different meaning than permissions for 'r''') permissions permit viewing regular file contents, files'''write''' ('''w''') permissions allow file contents . Refer to be modified/edited, and '''execute''' ('''x''') permissions permit the file diagrams to be run (e.g. running a '''program''' or '''shell script'''). Again, these permissions relate the right to see the 3 categories: '''user''' (owner), '''same group members''', '''other group members'''explanation of permissions and how they differ between a directory and a regular file.

The permissions of '''NOTE:''' The symbol 'newly-created'dash'' "directories and regular files are automatically assigned<br>via a '''-user mask'''" indicates that (we will discuss this shortly). In order to change permissions for<br>directories and regular files, you would use the permission is '''NOTchmod''' grantedcommand.

The chmod can use '''symbols''' to '''add''', '''remove''', and '''set''' rwx permissions for user,<br>same group members, other group members or ALL categories: <table cellpadding="5" width="70%"><tr><th style="border-bottom: 1px solid black;text-align:left;">Command</th><th style="border-bottom: 1px solid black;text-align:left;">Description</th></tr><tr valign="top"><td width="40%"><span style="font-family:courier;font-weight:bold;">chmod ugo+x script.bashrwx</span></td><td>Add execute permissions to for the file '''script.bashuser''' so it can be run.</tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold">chmod u=rwx,go=x ~</spanbr></td><td>Set "'''pass-thrusame group members'''" permissions of your , and/or o'''home''' directory for same group members and other group members to navigate to other subdirectories (that may have access / view permissions).</tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">chmod go-w ~/shared</span></td><td>Remove write permissions for same ther group members and other group members for the directory '''~/shared'''</td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">chmod for a=rx mydirectory or reqular file.</spanbr></tdbr><td>Set read and execute permissions for the directory '''myfile.txt'''</tdbr></tr></tablebr>  

[[Image:octal -permissions.png|thumb|right|400px150px|using Using octal numbers to represent setting file permissions.]]You can also use '''octal numbers''' to represent '''set''' permissions. Since 1 octal digit represents 3 binary digits, one octal digit can represent This method is a short-cut and may require less typing than using the rwx permission granted or NOT granted''symbolic'' method. The You can only use this method to set file permissions rwz would be in the form of 3 binary digits (1 represents the permission granted and 0 represents the permission NOT grantedas opposed to ''add'' or ''remove'' permissions.<br>x<br>x<br>

<table cellpadding="5" width="70%"><tr><th style="border-bottom: 1px solid black;text-align:left;">Command</th><th style="border-bottom: 1px solid black;text-align:left;">Description</th></tr><tr valign="top"><td width="40%">Since 1 octal digit represents 3 binary digits, one octal digit can represent the <span style="font-family:courier;font-weight:bold;">chmod ugo+x script.bashrwx</span></td><td>Add execute permission granted or NOT granted. The permissions to the file '''script.bashrwx''' so it can are be run.</tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold">chmod u=rwx,go=x ~</span></td><td>Set "'''pass-thru'''" permissions in the form of your '''home''' directory for same group members and other group members to navigate to other subdirectories 3 binary digits (that may have access / view permissions).</tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">chmod go-w ~/shared</span></td><td>Remove write permissions for same group members and other group members for 1 represents the directory '''~/shared'''</td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">chmod a=rx my</span></td><td>Set read permission granted and execute permissions for 0 represents the directory '''myfilepermission NOT granted).txt'''</td></tr></table>

For this investigation, we will NOT be logged into our Matrix account, but it is recommended to have sheets of paper ready an '''MS Word document'''<br>open to manually perform numbering conversationsconversions.

<span style="color:blue;">'''NOTE:''' It is essential that you learn how to <u>manually </u> perform numbering conversions since you will NOT be permitted to perform quizzes, midterm, or your final exam with a computer or a calculator. Learning to quickly perform manual numbering conversions will may make IT professional more productive such as setting permissions, designing computer networks, or selecting complex colors when developing webpages.</span>

# Let's convert the following ''8-bit'' binary number '''10111110''' to a '''<u>decimal number</u>'''.<br><br><span style="color:blue;">'''NOTE:''' It is extremely important to learn and '''memorize''' the '''correct techniquesmethods''' to perform the<br>proper numbering conversion method (i.e. view the '''method 1''' above (drawing the L's).</span><br><br># Write the manual conversion on a sheet of papereither in your MS Word document.<br><br># Use a '''calculator ''' to check your work. In MS Windows, you can set the calculator to Programming mode <br>by making the selection to '''binary''', enter the binary number '''10111110''' and view the decimal equivalent.<br><br>Did you get the correct answer? If not, <u>retry </u> the method and check to see what you did wrong.<br><br># Perform a manual conversion of the '''decimal number 55''' to an a '''8-bit <u>binary number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''octal number 461''' to an a '''8-bit <u>binary number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''8-bit binary number 11110001''' to a '''<u>hexadecimal number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''hexadecimal number ABC''' to an a '''8-bit <u>binary number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''binary number 10101111''' to an '''<u>octal number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the same '''binary number 10101111''' to a '''<u>hexadecimal number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''octal number 5636''' to a '''<u>hexadecimal number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># Perform a manual conversion of the '''hexadecimal number D68''' to an '''<u>octal number</u>'''.<br>What method (displayed above) will you use? Use a calculator to check your work.<br><br># When you have performed all of the numbering conversions above, then you can proceed to the next INVESTIGATION.<br><br>

'''Perform the Following Steps:''' # '''Login''' to your matrix account and issue a command to '''confirm''' you are located in your '''home''' directory.<br><br># Issue a single Linux command to create the following directory structure displayed in the diagram to the right.<br><br>'''NOTE:''' You will now run a shell script to confirm that you properly created that directory structure<br>in your ''Matrix'' account.<br><br># Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week4-check-1</span><br><br># If you encounter errors, make corrections and '''re-run''' the checking script until you<br>receive a congratulations message, then you can proceed.<br><br>[[Image:file-permission-practice-2.png|right|450px|thumb|]]# Issue Linux commands to create '''<u>empty</u> files''' for each of those newly created '''directories''' as shown in diagram to the right:<br><br>'''NOTE:''' You will now run another shell script to confirm that you properly created those empty files within those specified directories.<br><br># Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week4-check-2</span><br><br># If you encounter errors, make corrections and '''re-run''' the checking script until you<br>receive a congratulations message, then continue the remaining steps.<br><br>Let's get practice '''viewing permissions''', '''changing permissions''', and <u>automatically</u> '''setting permissions for newly created files'''.<br><br># Issue the following Linux commands:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls -ld ~/documents ~/clients ~/vendors<br>ls -lR ~/documents ~/clients ~/vendors</span><br><br>'''NOTE:''' You should see permissions already set for those newly created directories and regular files.<br>What do these permissions mean for '''same group member''' and '''other group member''' access to those directory and regular files?<br><br># Let's limit access to the '''clients''' and '''vendors''' directories to only yourself and same group members.<br>Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod 750 ~/clients ~/vendors</span><br><br># Issue the '''ls -ld''' and '''ls -lR''' commands (as you did in ''step #8'') to confirm that the permissions for those directories have been changed.<br><br>'''NOTE:''' The '''-R''' option for the '''chmod''' command can change the file permissions <u>recursively</u> within a directory structure.<br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">chmod 750 -R ~/documents</span><br><br># Issue the '''ls -ld''' command to confirm the permissions for the<br>'''~/documents''', '''~/document/memos''' , '''~/documents/reports''', and '''~/documents/contracts''' directories.<br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">ls -lR ~/documents</span><br>What do you noticed happened to the permissions for the regular files contained in those directories.<br>Did those regular file permissions change?<br><br>We will now change permissions for regular text file contained in subdirectories<br>of the '''documents''' directory to: <span style="font-weight:bold;font-family:courier;">r w - r - - - - -</span><br><br># Issue the following Linux commands: <br><span style="color:blue;font-weight:bold;font-family:courier;">chmod 640 ~/documents/memos/memo*.txt<br>chmod 640 ~/documents/reports/report*.txt<br>chmod 640 ~/documents/contracts/contract*.txt</span><br><br># Issue the <span style="font-weight:bold;font-family:courier;">ls -lR</span> command for the '''~/documents''' directory to confirm that those regular file permission have changed.<br><br>Let's run a checking script to make certain you correctly set permissions for those directories and files.<br><br># Issue the following: <span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week4-check-3</span><br><br># If you encounter errors, make corrections and then re-run the checking script until you receive a congratulations message<br>and then continue with this tutorial.<br><br>Let's get some practice setting permissions to allow users to make editing changes to regular files.<br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">chmod ugo-w ~/documents/memos/memo*.txt</span><br><br># Use the <span style="font-weight:bold;font-family:courier;">ls</span> command to verify that those regular file's permissions have changed.<br><br># Using the nano or vi text editor, open the regular file '''~/documents/memos/memo1.txt'''<br>and type in some text and try to save your editing changes.<br>What happened?<br><br># To <u>'''abort'''</u> your editing session in '''vi''': type <span style="color:blue;font-weight:bold;font-family:courier;">:q!</span> and press '''ENTER'''.<br>To <u>'''abort'''</u> your editing changes in '''nano''': type <span style="color:blue;font-weight:bold;font-family:courier;">ctrl-x</span><br>type <span style="color:blue;font-weight:bold;font-family:courier;">n</span> and then press '''ENTER''' when prompted to save editing changes.<br><br># Issue the following Linux command to add write permissions for all files in the '''memos''' directory<br>for yourself (i.e. user): <span style="color:blue;font-weight:bold;font-family:courier;">chmod u+w ~/documents/memos/*</span><br><br># Repeat steps to edit the file '''~/documents/memos/memo1.txt''' (as you did in ''step #20'').<br>Were you able to edit the file and save your editing changes?<br><br># Issue a Linux command to view the <u>contents</u> of the '''~/documents/memos/memo1.txt'''<br>text file that you were able to edit.<br><br># Issue the following Linux command to view permissions for your '''home''' directory: <span style="color:blue;font-weight:bold;font-family:courier;">ls -ld ~</span><br><br>What does execute permissions mean for same group members and other group members<br>in terms of your '''home''' directory?<br><br># Issue the following Linux command to create a new subdirectory: <span style="color:blue;font-weight:bold;font-family:courier;">mkdir ~/shared</span><br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">ls -ld ~/shared</span><br><br>What are the permissions for this newly-created directory?<br>Can other users access the directory pathname '''<span style="font-family:courier">~youruserid/shared</span>''' ?<br><br># Issue the following Linux command (without an argument): <span style="color:blue;font-weight:bold;font-family:courier;">umask</span><br><br>'''NOTE:''' You should see a '''four-digit octal''' number. Drop the leading zero on the left to obtain the '''default umask value'''.<br><br># Perform a '''mathematical calculation''' by taking the octal number '''777''' and <u>subtracting</u><br>the default umask value you determined in the previous step. What is the result?<br><br># Convert that octal number result to a '''binary''' number. What does that represent as newly created directory permissions?<br>Does that correspond to the permissions for the newly created '''~/shared''' directory?<br><br># Repeat the calculation (like in step #28) but with a umask setting of '''077''' to see how this new umask setting would<br>affect permissions of newly-created directories.<br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">umask 077</span><br><br># Issue the following Linux command (without arguments): <span style="color:blue;font-weight:bold;font-family:courier;">umask</span><br><br>NOTE: You should notice the value '''0077'''. By dropping the leading zero to the left,<br> that would provide the default '''umask value of 077'''.<br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">mkdir ~/shared2</span><br><br># Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">ls -ld ~/shared2</span><br><br>Do the permissions for this newly created directory match the predicted permissions that you calculated in '''step #30'''?<br><br># Issue the following Linux command to create an empty regular file called '''myfile.txt''' in the '''~/shared2''' directory:<br> <span style="color:blue;font-weight:bold;font-family:courier;">touch ~/shared2/myfile.txt</span><br><br># Use the <span style="font-weight:bold;font-family:courier;">ls -l</span> command to view the permissions for this newly created regular file.<br><br>What do you notice about those permissions?<br><br>Let's run a checking script to make certain you correctly set permissions for those recently-created directories and files.<br><br># Issue the following: <span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week4-check-4</span><br><br>If you encounter errors, make corrections and then re-run the checking script until you receive a congratulations message<br>and then continue with this tutorial.<br><br># Logout of your Matrix account, and then log-back into your Matrix account.<br><br># Issue the following Linux command (without arguments): <span style="color:blue;font-weight:bold;font-family:courier;">umask</span><br><br>What happened? Referring to your notes, what do you need to do to make that umask value persistent?<br><br><span style="color:red;">'''WARNING''':<br>You should be <u>extremely</u> aware of your permissions since you may perform '''marked work''' for <u>other</u> courses on your '''Matrix''' server.<br>You should NOT set permissions to share your work with '''same group''' or '''other group''' members (unless given '''specific permissions instructions from your course professors'''). If students can have access to your directories and project files, they could '''copy''' your work and thus make yourself and other student(s) that copied your work to be charged with '''academic dishonesty'''.</span><br><br>: Complete the Review Questions sections to get additional practice.<br><br>

The purpose of this section is to obtain extra practice to help with your assignment #1, quizzes, your midterm, and your final ezamexam.

https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_week4_practice.docx

# List the number of digits for the following numbering systems:<ul><li>'''Decimal'''</li><li>'''Binary'''</li><li>'''Octal'''</li><li>'''Hexadecimal'''</li></ul><br># Write a simple chart to show which values are represented for letter '''A - F ''' for a hexadecimal number.# How many '''binary ''' digits does 1 octal digit represent? # How many '''binary ''' digits does 1 hexadecimal digit represent?[[Image:number-conversion-chart.png|right|450px|thumb|]]# Use '''manual numbering conversion ''' to complete the table displayed to the right.  <ol><li value="6">Write the '''chmod''' command (using the ''symbolic'' method) to set “'''pass-through'''” permissions<br>(eg. <span style="font-family:courier;font-weight:bold;">r w x - - x - - x</span>) for your '''home''' directory using an '''absolute pathname'''.<br>Write a Linux command to verify that permissions where set.<br><br><br></li><li>Perform a binary to octal numbering conversion for the permissions: '''r w x - - x - - x'''<br>Write single Linux command to set “'''pass-through'''” permissions for your '''home''' directory,<br>using the '''absolute method''' (i.e. octal numbers).<br><br></li><li>Write a single Linux command to '''add read permissions''' for '''same group members''' for the '''~/tests''' directory.<br><br></li><li>Write a single Linux command to '''remove write permissions''' for '''same group members'''<br>and '''other group members''' for the '''~/projects''' directory. Use the ''symbolic'' method.<br><br></li><li>Write a single Linux command to set the permissions for the '''~/assignments''' directory<br> to the following using the '''absolute''' method (i.e. octal numbers): '''r w x r - x - - x''' <br>Show your work to perform a '''binary''' to '''octal''' conversion.<br>Write the command below using octal numbers and using a relative-to-home pathname.<br><br></li><li>Assume that you just issued the command:<br><span style="font-family:courier;font-weight:bold">chmod u=rwx,go=x ~/linux/content</span><br>What would be the new permissions for the “'''content'''” directory?<br><br></li><li>Assume that you just issued the commands:<br><span style="font-family:courier;font-weight:bold;">umask 077<br>mkdir mydir<br>touch mydir/myfile.txt<br></span><br>What would be the permissions for the newly created '''directory''' and '''regular file'''?<br>(show your work)</li></ol>   _________________________________________________________________________________

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