Proftpd TLS connection requires passive mode ports to be open if you are using a firewall.In this case UFW.
In the proftpd.conf file, find the below line and remove # from the start.You can narrow the ephemeral port range if you like.
PassivePorts startport endport
restart proftpd then add a firewall rule to that port range.
ufw allow startport:endport/tcp ufw disable && ufw enable
If you encountered freeze or halt while running ESXi installer on your system then probably your motherboard doesn't have Input–output memory management unit or it's disabled in the bios.So this is what you must do for it.When you boot from ESXi you must input a command at bootloader, which is "noiommu".This way you can boot your installer and install the system on the drive.
After the setup on first bootup, again you need to enter the "noiommu" command to your bootloader.After the system bootup you need to ssh into ESXi to change boot arguments indefinitely.First enable SSH to ESXi or on the shell
add the option "noiommu" to the "kernelopt" line and save it.
If you watched Interstellar movie, then you probably love the soundtracks of the movie.So why don't you enjoy it with a full of goosebumps on the way.