kazulog@sv1:~$ cat /etc/os-release | head -2
PRETTY_NAME="Ubuntu 26.04 LTS"
NAME="Ubuntu"
kazulog@sv1:~$ cat /etc/default/tftpd-hpa
# /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/srv/tftp"
TFTP_ADDRESS="192.168.100.10:69"
TFTP_OPTIONS="--secure --create"
kazulog@sv1:~$ cat /etc/hosts.deny
# /etc/hosts.deny: list of hosts that are _not_ allowed to access the system.
#                  See the manual pages hosts_access(5) and hosts_options(5).
#
# Example:    ALL: some.host.name, .some.domain
#             ALL EXCEPT in.fingerd: other.host.name, .other.domain
#
# If you're going to protect the portmapper use the name "rpcbind" for the
# daemon name. See rpcbind(8) and rpc.mountd(8) for further information.
#
# The PARANOID wildcard matches any host whose name does not match its
# address.
#
# You may wish to enable this to ensure any programs that don't
# validate looked up hostnames still leave understandable logs. In past
# versions of Debian this has been the default.
# ALL: PARANOID
# TFTP は 192.168.100.20 からの接続を拒否する
in.tftpd: 192.168.100.20
kazulog@sv1:~$ sudo ls -l /srv/tftp/
total 8
-rw-r--r-- 1 root root 27 Sep 12 10:01 hello.txt
-rw-rw-rw- 1 tftp tftp 18 Sep 12 10:02 upload.txt
kazulog@sv1:~$ systemctl is-enabled tftpd-hpa; systemctl is-active tftpd-hpa
enabled
active
kazulog@sv1:~$ sudo ss -ulnp 'sport = :69'
State               Recv-Q              Send-Q                            Local Address:Port                            Peer Address:Port              Process
UNCONN              0                   0                                192.168.100.10:69                                   0.0.0.0:*                  users:(("in.tftpd",pid=4631,fd=4))