Hello,
if you want to backup the host configuration using the command line, you can execute this two commands:
- vim-cmd hostsvc/firmware/sync_config (In order to save/sync the host configuration)
- vim-cmd hostsvc/firmware/backup_config (to backup the configuration)
The last command had better output something similar to this:
Bundle can be downloaded at : http://*/downloads/configBundle-localhost..tgz
Then, the backup can be downloaded connecting to this URL: http://IP_of_the_ESXi_Host/downloads/configBundle-localhost..tgz
If you want to restore the backup, this steps must be done:
- vim-cmd hostsvc/maintenance_mode_enter (put the host in maintenance mode)
- vim-cmd hostsvc/firmware/restore_config /tmp/configBundle.tgz (restore the backup using the backup file. Before, the backup file must be uploaded to a location accessible by the host)
I got this information from this vmware's kb:
And, we can call it a day! 
Best regards,
Pablo