usr0 page and images

+# CSCS1730 UNIX/Linux Fundamentals

+

+# PROJECT: UNIX SKILLS REVIEW (usr0)

+

+## OBJECTIVE

+

+To practice/review some previously utilized skills in order to obtain

+better mastery (assuming you've done the reading and successfully

+completed prior encounters with this topic), in combination with a

+specific focus on time management.

+

+It has been a while since we first encountered file permissions; yet they

+constantly remain ready to be put to use in our problem solving

+endeavours. I figure it would be a good time to have you review that

+concept, so this is a project dedicated to that, along with exploring

+them in further depth (and, well, time management).

+

+## REFERENCE

+

+Be sure you are familiar with the octal file permissions, as are used

+with the **chmod** command. You might want to check out:

+

+ * **chmod**(**1**)

+ * **chmod**(**2**)

+

+## REVIEW TOPIC

+

+For this week, the main topic of review will be file permissions. We see

+them when running an **ls -l**, for example:

+

+```

+lab46:/usr/local/bin$ ls -l s[uta]*

+-rwxr-xr-x 1 root staff 3126 Oct 3 2023 /usr/local/bin/sanitizehg

+-rwx------ 1 root staff 3646 Feb 25 2021 /usr/local/bin/sanitizewebfiles

+-rwxr-x--- 1 wedge lab46 763 Nov 19 2024 /usr/local/bin/status

+-rwxr-x--- 1 wedge lab46 11002 Apr 21 2022 /usr/local/bin/status.logic

+-rwxr-x--- 1 wedge lab46 16974 Mar 31 2024 /usr/local/bin/submit

+-rwxr-x--- 1 wedge lab46 7108 Oct 29 2021 /usr/local/bin/submitchk

+lab46:/usr/local/bin$

+```

+

+Of course, the file permission part is:

+

+```

+ -rwxr-x---

+```

+

+We split this into 3 fields (the leftmost dash is an additional field,

+and is for the file type) into user, group, and other.

+

+ * `-` indicates a regular file (not part of the file permission scheme)

+ * `rwx` corresponds to the user permissions

+ * `r-x` corresponds to the group permissions

+ * `---` corresponds to those who are neither the user nor the group

+

+Breakdown is as follows:

+

+ * read `(r)` is 4

+ * write `(w)` is 2

+ * execute/search `(x)` is 1

+ * nothing `(-)` is 0

+

+In any given field, we add up the values, which will result in a value

+within the range 0-7.

+

+So, in our example above, broken down showing the component permissions:

+

+

+```

+ u g o

+ - rwx r-x ---

+ 7 5 0

+```

+

+Practice: Come up with the file permissions for all the files listed in

+the example above. See how you fare.

+

+I wrote a tool for you to use in this project; it is called **urev**. It

+is located on and run on lab46.

+

+Your task will be to run this and complete a minimum of 144 problems

+(you'll be able to do a maximum of 192-- and those that do more than 144

+may see some benefit), in groups of 12 at a time (so you don't blow

+through them all in one sitting.. there's also a time delay before you

+can do the next set of 12-- so you clearly shouldn't wait until the last

+minute).

+

+To use **urev**, basically type in the 3 or 4 octal values matching the

+problem displayed (in the above example, you'd type in '7' '5' and '0',

+and upon input of each value, it will appear on the screen.

+

+If you get all 3 (or 4) correct, you'll earn a point. (Careful not to

+type too fast, otherwise the output may appear garbled).

+

+Any accumulated mistakes can be mitigated by doing problems in excess of

+the 144 required minimum. Once any mistakes have been nullified, some

+apportionment of bonus points can then be attained (not to exceed half

+the total points the project is worth).

+

+### PRACTICE PROBLEMS

+

+```

+- rwx r-x r-x /usr/local/bin/sanitizehg (755)

+- rwx --- --- /usr/local/bin/sanitizewebfiles (700)

+- rwx r-x --- /usr/local/bin/status (750)

+- rwx r-x --- /usr/local/bin/status.logic (750)

+- rwx r-x --- /usr/local/bin/submit (750)

+- rwx r-x --- /usr/local/bin/submitchk (750)

+```

+

+## 4TH TIER PERMISSIONS

+

+In addition to the classic three-valued permissions, there is an

+additional tier of permissions, corresponding to the "SetUID", "SetGID",

+and "Sticky Bit" modes. These represent a fourth value (the leading

+value).

+

+**Be aware:** Once you reach your 96th problem, this mode will be

+unlocked, and all modes entered will be 4-octal values long.

+

+To maintain general compatibility with the existing structure of the

+system, especially organization and real estate taken up by the display

+of the unix filemode string, this further tier of permissions instead

+overlays atop the 'x' fields of the user, group, and other fields.

+

+Breakdown is as follows:

+

+ * SetUID `(s)` has a value of 4

+ * this will manifest in the user field, overlaying its 'x' bit position

+ * 's' if 'x' is present, 'S' if 'x' is not present

+ * SetGID `(s)` has a value of 2

+ * this will manifest in the group field, overlaying its 'x' bit position

+ * 's' if 'x' is present, 'S' if 'x' is not present

+ * the Sticky Bit `(t)` has a value of 1

+ * this will manifest in the other field, overlaying its 'x' bit position

+ * 't' if 'x' is present, 'T' if 'x' is not present

+ * nothing `(-)` is 0

+

+```

+lab46:/usr/bin$ ls -l at procmail su

+-rwsr-sr-x 1 daemon daemon 59768 Oct 15 2022 /usr/bin/at

+-rwsr-sr-x 1 root mail 101664 Mar 1 2022 /usr/bin/procmail

+-rwsr-xr-x 1 root root 72000 Nov 21 2024 /usr/bin/su

+lab46:/usr/bin$

+```

+

+Of course, the file permission part is:

+

+```

+ -rwsr-sr-x

+```

+

+We split this into 3 fields (the leftmost dash is an additional field,

+and is for the file type) into user, group, and other.

+

+ * `-` indicates a regular file (not part of the file permission scheme)

+ * `rws` corresponds to the user permissions

+ * `r-s` corresponds to the group permissions

+ * `r-x` corresponds to those who are neither the user nor are in the group

+

+In any given field, we add up the values, which will result in a value

+within the range 0-7. The same is the case here.

+

+We start by computing the new, topmost tier:

+

+ * Is there an 's' or 'S' in the user field? If so: 4. If not: 0.

+ * Is there an 's' or 'S' in the group field? If so: 2. If not: 0.

+ * Is there a 't' or 'T' in the other field? If so: 1. If not: 0.

+

+Breakdown is as follows:

+

+ * user has an 's', so: 4

+ * group has a 's', so: 2

+ * other does not have a 't', so: 0

+

+Add them up: 4+2+0=6. That is our first value.

+

+We then proceed to process the remaining 3 tiers as before:

+

+ * user is 'rwx' (lowercase 's' indicates an 'x' underneath), for a: 7

+ * group is 'r-x' (lowercase 's' indicates an 'x' underneath), for a: 5

+ * other is 'r-x' (if there were a lowercase 't', it would indicate an 'x' underneath), for a: 5

+

+Final 4-tier octal permission for the example is therefore: 6755.

+

+Practice with the other examples, compare your results and see how you

+fare.

+

+You are to calculate this tier of permissions separate from the others

+(it is a distinct, separate fourth octal value, leading the classic

+three-valued permissions you've been working on so far).

+

+Over time, there may be changes in display form and difficulty. Think it

+through, answer with confidence!

+

+### PRACTICE

+

+```

+-rwsr-sr-x /usr/bin/at (6755)

+-rwsr-sr-x /usr/bin/procmail (6755)

+-rwsr-xr-x /usr/bin/su (4755)

+```

+

+## TIME DELAY

+

+To reinforce mastery, there is a time delay instituted to prevent

+accomplishing this task in one sitting. You will have to plan your time

+accordingly to perform this project in the time allotted.

+

+### PROJECT STATS

+

+A general overview of how the class has approached the project:

+

+

+

+where each color represents one individual's activity that day, stacked

+with that of others, enabling an overall per day general class activity.

+Higher bars and larger chunks of bars denote greater activity.

+

+And a more individual effort:

+

+

+

+where each line is an individual's cumulative progress over the set of

+days the project is available. The higher the line, the more work is

+being done.

+

+## HISTORICAL PROJECT RESULTS

+

+### FALL2025

+

+General:

+

+

+Individual:

+

+

+### SPRING2025

+

+General:

+

+

+Individual:

+

+

+### FALL2024

+

+General:

+

+

+Individual:

+

+

+### SPRING2024

+

+General:

+

+

+Individual:

+

+

+### FALL2023

+

+General:

+

+

+Individual:

+

+

+### SPRING2023

+

+General:

+

+

+Individual:

+

+

+## SUBMISSION

+

+Submission for this project is super-easy: simply complete the minimum

+required problems (144) by the deadline; no need to manually submit

+anything- just doing your **urev** allotments on lab46 is all that needs

+to be done.

+

+There is an opportunity to gain bonus points, and/or make up for mistakes

+made during the performing of this project, by doing more problems in

+addition to the 144 minimum.

+

+A central focus of this project is an enforced time management. You may

+want to plan ahead to make sure you budget the adequate time so you do

+not end up missing out.

+

+### RUBRIC

+

+I'll be evaluating the project based on the following criteria:

+

+```

+208:usr0:final tally of results (208/208)

+*:usr0:completed required 3-tier problems successfully [104/104]

+*:usr0:completed required 4-tier problems successfully [104/104]

+```

+

+**NOTE:** as with other projects, in order to get credit for the project

+it must be submitted. To submit this project, you must have completed 144

+problems. Not doing so will not garner you any points.