Como o artigo que você vincula diz em caracteres enormes antes da tabela, esse é o mecanismo tradicional . No Upstart, os runlevels 2-5 são os mesmos na configuração padrão:
4.7 Runlevels
A runlevel is a single-byte name for a particular system configuration. Runlevels for Debian and Ubuntu systems are generally as follows:
- 0 : System halt.
- 1 : Single-User mode.
- 2 : Graphical multi-user plus networking (DEFAULT)
- 3 : Same as "2", but not used.
- 4 : Same as "2", but not used.
- 5 : Same as "2", but not used.
- 6 : System reboot.
There are also a few pseudo-runlevels:
- N : The previous runlevel cannot be determined.
- S : Alias for Single-User mode.
O runlevel é 2 porque é o padrão.