difference between root executing command as sudo vs not using sudo?

Question

I have a Linux question regarding the sudo command and the root user. If I log into the root user using the su command, what is the difference between the following two commands?

root> sudo ./some_executable

and

root> ./some_executable

is there a difference? I am trying to use an executable and noticed that the executable works fine with the first command, but fails for the second command stating that I am not running the command as root. I always thought that the sudo/su commands allow you to execute commands with root privileges and so doing the first command would be redundant. However, I did noticed that the root user is in the sudoers file so I did not know if this is a bug in the executable or if there really is a difference between running a command logged in as root vs using sudo?

Answer 1

Your environment variables will be different for the two instances.

sudo will be resetting some of your environment variables - read the man page for sudo and look at the -E option as well as the section on the sudoers config file.

Additionally your use of su and not su - to gain root means you do not have a true root environment when executing the file directly.

In summary, you have an environment mismatch between the two situations making one work when the other doesn't.