Are you sure, you are in the karaf console?
Because if I ssh to karaf e.g. with
ssh -p 8101 openhab@localhost
from my ssh session,
the command could be found:
openhab> log:display
18:04:15.234 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.32 W to 5.21 W
18:04:30.248 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.21 W to 5.41 W
18:04:45.248 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.41 W to 5.23 W
18:04:48.580 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.23 W to 5.5 W
18:05:00.253 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.5 W to 5.51 W
18:05:15.257 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.51 W to 5.34 W
18:05:30.257 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.34 W to 5.33 W
18:05:45.257 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.33 W to 5.27 W
18:05:48.830 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'gShellyPCOfficeGroundFloor_Stromverbrauch' changed from 5.27 W to 5.34 W
In the meantime I did a complete new installation of 4.2.2 on my windows 10 machine. It seems that something went wrong while updating from 4.0.x to 4.2.2.
With a freh and new installation log:display is working fine. Now I have to migrate the old config to the new system. But this could be another story…