runlevel - Print previous and current SysV runlevel
"Runlevels" are an obsolete way to start and stop groups of services
used in SysV init. systemd provides a compatibility layer that maps runlevels
to targets, and associated binaries like runlevel. Nevertheless, only
one runlevel can be "active" at a given time, while systemd can
activate multiple targets concurrently, so the mapping to runlevels is
confusing and only approximate. Runlevels should not be used in new code, and
are mostly useful as a shorthand way to refer the matching systemd targets in
kernel boot parameters.
Table 1. Mapping between runlevels and systemd
|2, 3, 4
prints the previous and current SysV runlevel if they are known.
The two runlevel characters are separated by a single space
character. If a runlevel cannot be determined, N is printed instead. If
neither can be determined, the word "unknown" is printed.
Unless overridden in the environment, this will check the utmp
database for recent runlevel changes.
The following option is understood:
Print a short help text and exit.
If one or both runlevels could be determined, 0 is returned, a non-zero failure
If $RUNLEVEL is set, runlevel will print
this value as current runlevel and ignore utmp.
If $PREVLEVEL is set, runlevel will print
this value as previous runlevel and ignore utmp.
The utmp database runlevel reads the previous and
current runlevel from.