The traditional password file is maintained in /etc/passwd (as it contains more than just password information), but the actual encrypted passwords, along with expiration data, are kept in a file that can only be read or used by root (the Unix Administrator account).
Transit of Venus. A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun. The duration of such transits is usually measured in hours (the transit of 2012 lasted 6 hours and 40 minutes). A transit is similar to a solar eclipse by the Moon.
The best view of Venus came from the Magellan spacecraft, which entered orbit around Venus in 1990. Its cloud-penetrating radar mapped 98 percent of the planet's surface. Magellan discovered mountains on Venus that are taller than any on Earth, as well as a valley that is the longest and deepest in the solar system. Thousands of volcanoes dot the Venusian surface.