42.9. LABS 1 Exercise 42.1: Security and Mount Options

punko_brewster · November 2020

Hi All,

I am trying to understand one part of this lab, but am pretty confused. Step 2 instructs to "Copy an executable file to it from somewhere else on your system and test that it works in the new location." In the solution, we copy /bin/ls to mountpoint with "sudo cp /bin/ls mountpoint". This far I totally follow, but what comes next confuses me:
$ mountpoint/ls

Why does this work?
To test, I then also copied /bin/ps over and ran:
$ mountpoint/ps

This worked, also.
However, when I moved into ~/Documents and tried mountpoint/ls and mountpoint/ps they did not work, why?

punko@punko:~/Documents$ mountpoint/ls
bash: mountpoint/ls: No such file or directory
punko@punko:~/Documents$ mountpoint/ps
bash: mountpoint/ps: No such file or directory
punko@punko:~/Documents$

About my system:
punko@punko:~$ uname -a
Linux punko 4.15.0-124-generic #127-Ubuntu SMP Fri Nov 6 10:54:43 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
punko@punko:~$

coop · November 2020

if you actually typed what you said in your email you are missing a "/". it sounds like you simply copied to make a new file named "mountpoint" , it does not say mountpoint is a directory. So if you switch directories to somewhere else it cannot work. In other words it should be:

mkdir mountpoint
cp /bin/ls mountpoint
mountpoint/ls

But if you go somewhere else you have to give the full path as in:

cd /tmp
/home/student/mountpoint/ls

or wherever you put it.

punko_brewster · November 2020

Thank you! Tested, and now I understand is as you are just telling the system were to look for the command. That is the path in front, so if you switch from where you initially were when you copied the command, you have to tell the system where the command you want is located. Got it.

42.9. LABS 1 Exercise 42.1: Security and Mount Options

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