[ Thanks to Puru
Govind for this link. ]
“Many Windows users are familiar with different modes of
execution of their operating system: safe mode, command prompt
only, safe mode with network support and other such options that
are presented during the boot-up process. Similarly, Linux has
different modes of executing as well, which are known as runlevels.
But unlike Windows, we can change runlevels on a fly.“Runlevels control services started by the initialization
process. The number of runlevels and services started on those
runlevels varies with Linux distributions. Information about the
runlevels of a particular distribution is listed in file
/etc/inittab…”