Updated: 2015-09-06 00:38 EDT
Do not print this assignment on paper!
- On paper, you will miss updates, corrections, and hints added to the online version.
- On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.
- On paper, scrolling text boxes will be cut off and not print properly.
23h59 (11:59pm) Sunday September 21, 2014 (start of Week 4)
Do not print this assignment on paper! On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.
This is an overview of how you are expected to complete this assignment. Read all the words before you start working.
For full marks, follow these directions exactly.
You will create file system structure in your HOME directory, with various directories, files, and links. You can use the Checking Program to check your work as you do the tasks. You can check your work with the checking program as often as you like before you submit your final mark. (Some tasks sections below require you to finish the whole section before running the checking program; you may not always be able to run the checking program successfully after every single task step.)
When you are finished the tasks, leave these files, directories, and links in place as part of your deliverables. Do not delete any assignment work until after the term is over! Assignments may be re-marked at any time; you must have your term work available right until term end.
This is a review lab, and all of the tasks can be completed with knowledge of the material from the prerequisite course CST8207 GNU/Linux Operating Systems I; however, you will probably need to refresh your memory of various topics by referring to the CST8207 course notes and the Linux man pages. Your lab instructor is there to help you, but s/he will want you to have tried consulting the notes and man pages first.
The prevous term’s course notes are available on the Internet here: CST8207 GNU/Linux Operating Systems I. All the notes files are also on the CLS. You can learn about how to read and search these files using the command line on the CLS under the heading Copies of the CST8207 course notes near the bottom of the page Course Linux Server.
Since I also do manual marking of student assignments, your final mark may not be the same as the mark submitted using the current version of the Checking Program. I do not guarantee that any version of the Checking Program will find all the errors in your work. Complete your assignments according to the specifications, not according to the incomplete set of the mistakes detected by the Checking Program.
All references to the “Source Directory” below are to the CLS directory ~idallen/cst8177/14f/assignment01/
and that name starts with a tilde character ~
followed by a userid with no intervening slash. The leading tilde indicates to the shell that the pathname starts with the HOME directory of the account idallen
(seven letters).
Do a Remote Login to the Course Linux Server (CLS) from any existing computer, using the host name appropriate for whether you are on-campus or off-campus. Pay particular attention to the special non-Algonquin password you must use, or else you will lock yourself out of the machine. All work in this assignment must be done on the CLS.
Create the following directory structure in your CLS HOME directory and record (for study purposes) the series of Unix commands you used to create it. Spelling and capitalization must be exactly as shown:
CST8177-14F
`-- Assignments
`-- assignment01
This directory is the base directory for most pathnames in this assignment. Store your files and answers here.
There is a Checking Program named assignment01check
in the Source Directory on the CLS. Follow the instructions in the first two steps at the start of Checking Program to create a working symbolic link to this program.
If you haven’t taken the prerequisite course CST8207 GNU/Linux Operating Systems I using the CLS, you will need to read Startup Files to know what lines to place in your .bash_profile
and .bashrc
before beginning this assignment.
Check your work so far using the assignment01check
program symlink.
From your HOME directory, use the ls
command with options to give a long listing (showing permissions), include all hidden files, include inode numbers, and recursively include all subdirectories. (Do not use any other options.) When the output is correct, redirect the output of this command into new file listing_start.txt
under assignment01
– it will be at least 16 lines of output. (If you have files from other terms in your account, you may get some “permission denied” errors doing the listing [ignore the errors] and the number will be many more than 16 lines.)
Run the whoami
command. When the output is correct, redirect the output of this command into new file whoami.txt
under assignment01
Run the id
command. When the output is correct, append the output of this command to existing file whoami.txt
under assignment01
. (Note the word append). The file must now have two lines of output in it. Check it!
Rename the file whoami.txt
to have the new name whoamiid.txt
(in the same directory) and make extra sure you spelled the new name correctly.
Use a command to count only the number of lines (not characters or words) in file read.txt
in the Source Directory, using the absolute pathname of the file. (You’ll know you have the right file if the size is 838 characters.) When the output is correct (one line), redirect the output of this command (the output containing only the line count number and the absolute pathname, not any other numbers) into new file readlines.txt
under assignment01
Use a command to search for and display the single line containing the exact text phrase “permissions is useless
” located inside any one of the text files (files having a .txt
file extension) located in the notes/
directory of the previous term CST8207 (14W: Winter 2014). The Introduction and Overview explains where to find these notes and how to search them, just as you did last term. When the output is correct, redirect the one line of output of this command into new file useless.txt
under assignment01
The file should be one line long.
Check your work so far using the assignment01check
program symlink.
Copy the binary program file /bin/hostname
three times to files named read_only
, write_only
, and execute_only
under your assignment01
directory. This is a BINARY program file, so do not display the content of the file on your terminal screen!
Change the permissions on all three copied files so that group and other have no permissions. (You can do this with one command name and a file GLOB pattern.)
read_only
file so that only you can read the file but not write or execute the file.
/dev/null
.write_only
file so that only you can write (including append to) the file but not read or execute the file.
execute_only
file so that only you can execute the file but not read or write the file.
Check your work so far using the assignment01check
program symlink.
Make the following directory structure under assignment01/
permissions/
permissions/read_only/
permissions/write_only/
permissions/execute_only/
Change the permissions on the permissions/
directory so the owner (you) can read, write, and search, but group and other have no permissions.
Change the permissions on all three subdirectories of permissions/
so that that group and other have no permissions. (You can do this with one command name and a file GLOB pattern.)
Change the permissions on read_only/
so that you can see the names in the directory (with echo read_only/*
or similar), but cannot take an accurate long listing, and cannot create files, and cannot cd
into the directory. (Verify that you can/cannot do these things!)
Hint: Of course echo read_only/*
will only show file names if you actually create those files.
Change the permissions on write_only/
so that you cannot see the names in the directory, but you can add new files to the directory, delete files from the directory, and cd
into the directory. (Verify that you can/cannot do these things!)
Change the permissions on execute_only/
so that you can (only) cd
into the directory. You cannot see the names in the directory or add or delete files from the directory. Verify!
Check your work so far using the assignment01check
program symlink.
Under the Source Directory there is a directory named maze
(four letters). This maze contains many hidden sub-directories. Use a single command (no pipes needed) to find in the maze a single hidden file with a basename similar to .abcd0001*txt
, but look for the basename that starts with a period followed by your own Blackboard userid, not the fake userid abcd0001
. To look for the file, replace the string abcd0001
in .abcd0001*txt
with your own userid before you look. The basename you find must be exactly 13 characters long and contain a period and a real asterisk. It must have no leading or trailing blanks around it.
Hint#1: You might want to use a single command (not a pipeline) that finds files by basename to do this. (Do not try to use cd
and ls
to find your file; the maze is really big.)
Hint#2: If you want to find a name containing a real asterisk, you may need to escape the asterisk to stop it from being used as a pattern character (wildcard), and you need to do this both for the shell that reads your command line and for the command that finds the files. if you get the escaping right, you will find exactly one file.
When you find the right file basename (there is only one for your userid), put its shortest full absolute pathname into new file foundmaze.txt
under your assignment01
directory. Note: Shortest absolute pathnames contain no /./
or /../
or tilde (“~
”) expressions; simplify the path to the shortest possible absolute pathname.
Check your work so far using the assignment01check
program symlink.
assignment01
directory.thepasswd
thepasswd
symbolic link, e.g. wc thepasswd
must give exactly the same output as for the password file.Display the file attributes and inode numbers of both the password file and the thepasswd
symbolic link, and confirm that they are different. Unlike a hard link, a symbolic link is a separate inode.
thepasswd
symlink you just created:
assignment01
directory.alsopasswd
thepasswd
in the same directory. (See the Hint below.)alsopasswd
now links to absolute symlink thepasswd
that links to the password file.alsopasswd
symbolic link, e.g. wc alsopasswd
must work as expected.Hint: All of “././foo
” and “./foo
” and “foo
” are relative pathnames that lead to the same place. Which one is the shortest? Always use the shortest relative pathname. Don’t use ./foo
when all you need is foo
.
thepasswd
symlink to be otherpasswd
.
alsopasswd
is a broken relative symlink to a non-existent thepasswd
symlink.alsopasswd
to read the text of the password file, e.g. wc alsopasswd
no longer works.Definition: A broken or dangling symlink is a symlink to something that doesn’t exist. The alsopasswd
symlink is now a dangling symlink, since it links to the nonexistent thepasswd
.
Check your work so far using the assignment01check
program symlink.
Create a hard link to the read.txt
file in the Source Directory (you counted the lines in this file earlier); name the hard link hardlink
in the assignment01
directory. (Note; On some versions of Unix/Linux, you are not allowed to hard link to a file you cannot write. That protection has been disabled on the CLS.) Verify that you can read the file using the hardlink
hard link.
Display the file attributes and inode numbers of both the read.txt
file and the hardlink
hard link, and confirm that they are identical. (Only the pathnames will be different.) These hard links are just two names for the same file inode.
Make a new hard link to hardlink
named newhard
in the same assignment01
directory.
Display the file attributes and inode numbers of the read.txt
file and both the new hard link files, and confirm that all three are identical. (Only the pathnames will be different.) These hard links are just three names for the same file inode.
Rename hardlink
to junkread
and note that this does not break the hard link for newhard
. Verify that all three files have the same attributes and inode numbers and that you can read the text of the read.txt
file through both hard links, as before.
Check your work so far using the assignment01check
program symlink.
Make a backup copy of your listing_start.txt
file, in case you accidentally overwrite it in the next step.
From the same starting directory, repeat the command you used to create listing_start.txt
at the beginning of this lab, but redirect the output this time into the file listing_end.txt
in the same directory as listing_start.txt
, and make sure that all errors (standard error output) also go into the output file and not on the screen.
Hints: The first five words in the previous paragraph are very important. You might find your shell history useful here. There is a special syntax to also redirect error messages into a file using Shell I/O Redirection.
Use the diff
command to compare the earlier listing file to the previous one you did before starting this lab. Note the many changes!
That is all the tasks you need to do.
Check your work a final time using the Checking Program and save the output as described below. Submit your mark following the directions below.
Summary: Do some tasks, then run the checking program to verify your work as you go. You can run the checking program as often as you want. When you have the best mark, upload the marks file to Blackboard.
Since I also do manual marking of student assignments, your final mark may not be the same as the mark submitted using the current version of the Checking Program. I do not guarantee that any version of the Checking Program will find all the errors in your work. Complete your assignments according to the specifications, not according to the incomplete set of the mistakes detected by the Checking Program.
There is a Checking Program named assignment01check
in the Source Directory on the CLS. Create a Symbolic Link to this program named check
under your new assignment01
directory on the CLS so that you can easily run the program to check your work and assign your work a mark on the CLS. Note: You can create a symbolic link to this executable program but you do not have permission to read or copy the program file.
Execute the above “check” program on the CLS using its symbolic link. (Review the Search Path notes if you forget how to run a program by pathname from the command line.) This program will check your work, assign you a mark, and display the output on your screen. (You may want to paginate the long output so you can read all of it.)
You may run the “check” program as many times as you wish, to correct mistakes and get the best mark. Some task sections require you to finish the whole section before running the checking program at the end; you may not always be able to run the checking program successfully after every single task step.
assignment01.txt
under your assignment01
directory on the CLS. Use the exact name assignment01.txt
in your assignment01
directory. Case (upper/lower case letters) matters. Be absolutely accurate, as if your marks depended on it.
YOUR MARK for
assignment01.txt
file from the CLS to your local computer and verify that the file still contains all the output from the checking program. Do not edit this file! No empty files, please! Edited or damaged files will not be marked. You may want to refer to your File Transfer notes.
YOUR MARK for
assignment01.txt
file from your local computer to the correct Assignment area on Blackboard (with the exact name) before the due date:
Use only Attach File on the Upload Assignment page. Do not enter any text into the Text Submission or Comments boxes on Blackboard; I do not read them. Use only the Attach File section followed by the Submit button. If you need to comment on any assignment submission, send me email.
You can revise and upload the file more than once using the Start New button on the Review Submission History page to open a new Upload Assignment page. I only look at the most recent submission.
You must upload the file with the correct name from your local computer; you cannot correct the name as you upload it to Blackboard.
You will also see the Review Submission History page any time you already have an assignment attempt uploaded and you click on the underlined assignment01 link. You can use the Start New button on this page to re-upload your assignment as many times as you like.
You cannot delete an assignment attempt, but you can always upload a new version. I only mark the latest version.
Your instructor may also mark files in your directory in your CLS account after the due date. Leave everything there on the CLS. Do not delete any assignment work from the CLS until after the term is over!
I do not accept any assignment submissions by email. Use only the Blackboard Attach File. No word processor documents. Plain Text only.
Use the exact file name given above. Upload only one single file of Linux-format plain text, not HTML, not RTF, not MSWord. No fonts, no word-processing. Linux plain text only.
NO EMAIL, WORD PROCESSOR, PDF, RTF, or HTML DOCUMENTS ACCEPTED.
No marks are awarded for submitting under the wrong assignment number or for using the wrong file name. Use the exact 16-character, lower-case name given above.
WARNING: Some inattentive students don’t read all these words. Don’t make that mistake! Be exact.
READ ALL THE WORDS. OH PLEASE, PLEASE, PLEASE READ ALL THE WORDS!