File with no permission accessed with sudo

Question

as no user have any permission to read file.txt,then why/how 'sudo cat file.txt' prints file contents?

bs01316@bs01316:~/test$ ls -l
total 4
---------- 1 bs01316 bs01316 6 মে        7 16:20 file.txt
bs01316@bs01316:~/test$ sudo cat file.txt 
hello

is superuser & root user samething or different concept?

Answer 1

root essentially ignores permissions on local files. r--r--r--, for example, doesn't give root permission to read a file so much as it excludes non-root users from reading it.

There is a slight distinction between root and superuser. root is a superuser, and usually the only superuser account, though other accounts can also be given superuser status. (Someone should check me on that, though.)

sudo is just a program that lets you run a program as any other user. The default (when the -u option isn't used) is to run a program as root.

Answer 2

if sudo(superuser) in /etv/sudouser have ALL=(ALL:ALL) ALL then it's have all privilege to do anything like the root. in this case sudo is above all like root no need to permission to do something.