Access control through group membership

sadamahan

Hello Everyone

Can someone please help me understand why user smk cannot access a folder /root/quotamnt when user smk belongs to a valid group (root) that is authorized to access the folder (/root/quotamnt).

Have a folder /root/quotamnt that allows users in group "root": 

root@SandBox1:~# ls /root/quotamnt

drwxr-xr-x  3 root root 1.0K May 24 14:41 quotamnt

Then added user smk to group "root":

smk@SandBox1:~$ sudo usermod -a -G root smk

Verify it exists:

smk@SandBox1:~$ groups smk

smk : smk root adm cdrom sudo dip plugdev lpadmin sambashare

Logged out and logged back in as smk.

Why can't smk access /root/quotamnt:

smk@SandBox1:~$ ls /root/quotamnt

ls: cannot access '/root/quotamnt': Permission denied

Thanks in advance!

SMK

 

 

luisviveropena

Hello SMK,

Are you sure you want to add a normal user to the root group? Is that a good idea? If you want to know why you can't access that directory you can see it here:

ls -l /

Regards,

Luis.

sadamahan

Hello Luis

Thank you for your response. I am attempting to add a normal user to the root group only to learn the concepts - would not do that on a live system. 

If a user is in the root group, I believe they should have access to everything that root does. I see the output of ls -l / but that does not make it clear to me why I cannot access a folder /root/quotamnt. 

Best Regards

SMK 

sadamahan

Hello Luis

Thank you for your response. I am attempting to add a normal user to the root group only to learn the concepts - would not do that on a live system. 

If a user is in the root group, I believe they should have access to everything that root does. I see the output of ls -l / but that does not make it clear to me why I cannot access a folder /root/quotamnt. 

Best Regards

SMK 

sadamahan

Hello Luis

Thank you for your response. I am attempting to add a normal user to the root group only to learn the concepts - would not do that on a live system. 

If a user is in the root group, I believe they should have access to everything that root does. I see the output of ls -l / but that does not make it clear to me why I cannot access a folder /root/quotamnt. 

Best Regards

SMK

luisviveropena

Hello Sadamahan,

You may start studying Chapter 35. File permissions and ownership, I think that should be enough to understand this. If after that you still are unclear, please go back here.

Regards,

Luis.

coop

Please try adding to another group, not root.  Not only is this a very very bad idea, but exactly what would happen is likely to differ on different systems.  I have never seen someone do this.