On UNIX this special user is known as superuser or root (not to be confused with the root directory). Superuser can override file security and do almost anything she wants on the system (she cannot see your password, since it is encrypted, but she can change it). In fact, any user with a userid of 0 is a superuser. Naturally, such users should always have a password.
not good practice for the system administrator
to always logon as superuser. It is too easy to make a trivial mistake
and damage the system, perhaps by
rm * in an
important directory. Instead, logon as a regular user, then
switch to superuser with the su command when you need it.
Root is Also the Start of the Directory
In a Hierarchical File System, one
directory is the root or start of the tree. Other
directories hang off root and they in turn can have
subdirectories. On UNIX and
POSIX, root is specified as a
forward slash "/". On DOS, root is specified as a
backward slash "\".
This meaning of root should not be confused with the alternate
meaning of root as the UNIX system manager (that is,