Very slow reboot or shutdown

On my machine there is a unit session-2.scope too:

**erlangen:~ #** systemctl list-units --type scope  
  UNIT            LOAD   ACTIVE SUB     DESCRIPTION               
  init.scope      loaded active running System and Service Manager 
  session-2.scope loaded active running Session 2 of user karl 

LOAD   = Reflects whether the unit definition was properly loaded. 
ACTIVE = The high-level unit activation state, i.e. generalization of SUB. 
SUB    = The low-level unit activation state, values depend on unit type. 
**2 loaded units listed.** Pass --all to see loaded but inactive units, too. 
To show all installed unit files use 'systemctl list-unit-files'. 
**erlangen:~ #**

In the first place it’s me who is creating this unit by logging in.