Run these commands on each switch to be able to run NCLU commands without sudo, change the hostname and bring up the interfaces. Exit the switch, then log back in to see the new hostname at the prompt.
cumulus@cumulus:mgmt:~$ sudo usermod -a -G netedit vagrant cumulus@cumulus:mgmt:~$ net add hostname leaf01 cumulus@cumulus:mgmt:~$ net add interface swp1,swp2,swp3 cumulus@cumulus:mgmt:~$ net commit cumulus@cumulus:mgmt:~$ exit
cumulus@cumulus:mgmt:~$ sudo usermod -a -G netedit vagrant cumulus@cumulus:mgmt:~$ net add hostname leaf02 cumulus@cumulus:mgmt:~$ net add interface swp1,swp2,swp3 cumulus@cumulus:mgmt:~$ net commit cumulus@cumulus:mgmt:~$ exit
cumulus@cumulus:mgmt:~$ sudo usermod -a -G netedit vagrant cumulus@cumulus:mgmt:~$ net add hostname spine01 cumulus@cumulus:mgmt:~$ net add interface swp1,swp2 cumulus@cumulus:mgmt:~$ net commit cumulus@cumulus:mgmt:~$ exit