unable to cd into /var/log/audit
 

User and others dont have any permission.
So i tried to cd using sudo

It is not changing the directory.

Do i have to change the file permission?

No, it's doing exactly what it should. You started a shell with elevated privileges, and the command ran successfully....upon which the sudo shell exited. Either start an interactive sudo shell with "sudo -s" and cd into that folder, or use "su - root" and run it.

I never know this.
From your words, sudo cd audit => i started the shell with sudo privileges

cd audit -> it changed the directory to audit (ran the command successfully)

i lost the privilege in the shell, so i came one directory up??
Or it never reached audit directory.?

i dont know the root password. I think i have not set one. Fedora did not come up with root password.
But it is awesome to know that i can change the shell with this command sudo -s

Now it is changed to root@fedora

visudo
If i change the third ALL to some specific command, then i can execute those commands only as a root. Is that right?
How does the shell knew this? ("this (mahesh)" root is not allowed to mount, unmount, etc...)
Because my shell become root@fedora

Be careful! Linux denies privileges to ordinary users for a good reason. It is rather easy to do something destructive when playing about as root. Yes, you can cheat by calling up a root shell, but it is always safer to use sudo. Having to prefix "sudo" to a command is psychologically useful: it reminds you that you are about to wield a potentially dangerous power and that you need to visually check the command for potential trapdoors before you press Enter.

Being a member of the wheel group does not make you root. I just tested it (I am a member of wheel on my machine and my sudoers file has the same line in it as yours does) but I still can't mount a partition that has been set as non-user-mountable or read the sudoers file. In other words I can use the commands but the result is not necessarily what I want.

Edit: I must have had a memory lapse! Of course it means that you can use sudo with any command, not just with some. It does not apply to commands used without sudo.

yes, but not only started a new shell, you also passed a command to execute inside (that is cd audit)
No, it was successfully executed, you got no any error messages (like permission denied or similar).
But as it was mentioned your shell completed the command you specified and exited. At the end you returned back to the initial shell and also into the initial directory.

You can check it for example by executing:(or something like this)

Did you read the man pages on sudo?? You need to do research on what things are and how they work.
Again, read up on what things do and how. If you type in "sudo -s" you get a root-equivalent shell...you are (essentially) logged in as root. If you run "sudo /some/command", it will execute that ONE COMMAND. The two aren't the same.

Just learning linux. (last one week) That is why i am trying everything. Without trying out, it is not possible to learn i think. Just reading is not good enough. even if i broke something, it does not matter. Just using linux on old machine to learn.

I thought linux is easy to learn. It seems it is a life time learning...
Man page is really confusing me. I am not able to understand clearly what a man page is trying to explain.
So using youtube and some books.

But i am not happy. Can you please suggest me a book which can teach me the basics as well as advance concepts of linux.
Just basics is not enough.

When i try to learn about networking commands, Those are really difficult for me. It seems i need networking knowledge to understand about those commands.
Instead of man pages, Please suggest some good linux books. So i can gain some knowledge..

Thanks a lot for your help

I learned everything I needed to know about my first Linux system by reading Running Linux. It's quite old now but I can still recommend it. Most Linux books are distro-specific but that one is not. For advice on how to understand man pages, https://www.linuxquestions.org/quest...n-pages-38130/.

There is no such thing, you cannot learn linux. You can learn a lot of different things, like how does a computer work, what is a kernel or programming language, how can we connect computers, and a huge amount of other things.
Again you cannot learn linux, but some parts of the system (first, and some other parts later). man pages are not really good for beginners, it is true, but youtube, books, tutorials, examples can be really useful.
It is a life-time journey, you can decide which part is important for you or interested in. Probably others will suggest a lot of books and other resources, I would only suggest you to practice.
Yes, networking is a complex issue, I totally agree with you. But you can find a lot of topics about it on the net. As an example:
https://www.youtube.com/watch?v=61yMjSjgnVc

And did you learn everything about Windows in a few minutes from reading a page or two??? Why would Linux be different??
The man pages for a command explain THAT COMMAND. It tells you how to use it, what it does, and what all the options are. It's a help document.
Why would you think you wouldn't need to know network knowledge to understand what networking commands do??
You need to load Linux and actually use it. It is just not hard, and instead of thinking you're going to read a book and get good, you need to use it, just like you learned Windows right??? Load it..and if you have a problem, you then do research on how to solve it, and post here if you can't figure it out. Solve your problems one at a time...again, exactly like you did with Windows.

sudo runs one external command.
But a working cd must be an internal (shell builtin) command.
For some reason there is also an external cd command in many Linux distros:
runs the /bin/cd and it does not have a lasting effect.
Test it in the shell:
does not have a lasting effect.
Behind the scenes the shell forks/clones another shell that execs/converts to the command.
This is not necessary for an internal command.
Another internal command: set
sudo does not find it because it is not an external command.
In
The sudo runs /bin/bash,
which runs the internal cd command, an internal pwd command (that could be external as well), and an external ls command.

Fascinating. Slackware does not include a separate cd command btw. I just checked.

there is no external cd command, it is just pointless. I mean not in slackware, but in general. What would it (or could it) do at all?
Open a new process, cd into somewhere and exit?

A discussion is here
A temporary cd can make sense because a test -d just checks the attributes.
But if you really need it then you can use a short embedded bash script:
Same technique as for sudo.

And directly in bash you can use a sub shell: