Thanks for all the postings, I have learned a lot regarding OMV from this forum.
Recently, I have difficulty in installation of Portainer in omv 5.x. One solution is that re-configuration of network after entering "omv-firstaid".
After installation of docker the network interface is broken and DNS does not work.
Use omv-firstaid to reconfigure the network interface. After that installation of Portainer worked for me.
However, after I tried to follow steps in ssh, the lines in terminal frozen at "in configuration, please", something like that, for a long time.
Then I force to close the terminal, and found out that I cannot re-connect to server using original IP address.
After I type "IP addr", the new address doesn't work either.