Su:incorrect Password

When switching to the root user using the SU (SU-) command in a state with normal user login: su:incorrect password, but you can log in to the operating system directly using the root user and password.

Solution:

may be related to the properties of Su, the execution file.

The permissions should be "-rwsr-xr-x"

The properties of SU in your own system are "-rwxr-xr-x"

That is, Su is executable to the user, but still the user's permissions.

Finally found the reason. When performing su with a normal user, only on behalf of the user, although executed, but access to other resources, such as password files, may not have permission.

Log in to the operating system directly with the root user and modify the/bin/su file properties

chmod u+s/bin/su modified to "-rwsr-xr-x", then su switch, all OK.

PS: Quality s bit, the executor does not represent the caller, but represents the owner and has owner permissions. The SU owner is root, so the normal user performs su with root privileges, access to the password and other protection resources.

Su:incorrect Password