Linux Sysadmin Basics -- Linux File Permissions

How do file permissions work on Linux? How can I make a Linux file readable or executable? This is a basic overview (without diving into Binary notation) of Linux and Unix file permissions. In other words, you'll finally be able to decode everything you see when you type "ls -l".

[VperVendetta]

Read=4
Write=2
Xecute=1
It's not that difficult. You just add the ones you want:
4+2+1 = (r+w+x) = 7
4+2 = (r+w) = 6
4+1 = (r+x) = 5
4 = (r) = 4
2+1 = (w+x) = 3
2 = (w) = 2
1 = (x) = 1

[balsabjelogrlic]

made it this far and I'm thinking, this guy dedicated all this time to explain Linux without any payoff, thank you so much man! Very helpful videos, cheers! :)

[berkelunstad]

Thanks for the video, it was super helpful. The one thing I would add would be an easy way to remember the different chmod values without having to look them up. Each number 0-7 represents an addition of 0 to 3 of the following numbers: 4 represents read, 2 represents write, 1 represents execute. So a 6 means rw- (4+2) and a 2 means -w- and a 0 means --- and so on.


Edit: In retrospect this is just because of binary, rwx = 111 and r-x = 101 and so on. I didn't realize this until the next morning. Perhaps this is why I shouldn't try to learn Linux at midnight lol.

[usingvancedplzdontban]

chmod notations @ 3;20: (easier to memorize in descending order actually)

0: - - - (no rights at all)
1: - - x
2: - w -
3: - w x
4: r - -
5: r - x
6: r w -
7: r w x

[JnDaFraK]

By playing around with chmod, I've found out that you need to have both read and execute privileges in order to view the directory content and file attributes.
Setting the value to 1 (execute only) will lock you out of the directory, preventing you to see its content.
Setting the value to 4 (read only) allows you to see the directory contents but the file attributes aren't accessible.
Cool, lots of new stuff learned today, thanks.

[BorrellRicard]

Thank you for these videos. I work in a research group in Computational Fluid Dynamics, we all use Linux and supercomputers but most of us learn just what we need and much less that what could be useful for us. Definitely,  I'll recommend your entire course to new students coming to our lab.

[nadiakateb]

Thank you so much sir !!! I've seen a lot of videos about linux on youtube and yours are the best. You have a an incredible way for making everything so simple and easy to understand.

[classicsagat]

Been enjoying this Linux series! All of this has been really informative and well structured, thank you so much!

[habituallearner]

Thanks so much. It's very kind and thoughtful of you to create and update this series. It's quite comprehensive and is a great review for me.

[saltdomeguy]

Loving this series Dave. New to Linux, so this is gold. Thanks!

[klaraschumann]

Your videos really are an eye opener.
Thanks for the effort.

[GabrielMartinez-ezue]

Excellent. I have been following your tutorials with a book called: Linux Pocket Guide. Thank you

[kennethnicklowicz]

Amazing the moment you realize you've been using CHMOD and have an idea now what its actually doing KUDOS!

[nikolamilic]

These videos are the best...you too. Thx a lot!

[PunmasterSTP]

Permissions? More like “Perfect explanations!”

[abhimanyuvi]

Hats off to you sir, very nice videos
thanks for making such nice videos

[Stevesteacher]

Amazing, this helped me so much with chmod! thank you :)

[manningermani]

if you don't want to learn the numbers you can use 'chmod u+x script' for example, to add execute rights to the user

[newwavex]

Could you do a video on binary and octal notation? I have a hard time understanding it, aswell as hexadecimal

[garretmkiii]

So for each owner/group/user there are positions OWNER 2^2, 2^1, 2^0; GROUP 2^2, 2^1, 2^0; and USER 2^2, 2^1, 2^0, where each position can be either 1 or 0 (yes/no, true/false).
If position OWNER 2^2 = true (1), file is readable by OWNER, and since the "true" is in position 2^2, it's evaluated as 4.
to make a 7, all bits have to be true (1), re: 2^2 + 2^1 + 2^0 = 4 + 2 + 1 = 7, in which case the file can be read, written to and executed for the respective user.

And now I'm just going to copy and paste my comment into my YouTube Course Notes. :P