Port 2222
ListenAddress 0.0.0.0
HostKey /run/sshd/ssh_host_ed25519_key
PidFile /run/sshd/sshd.pid
AuthorizedKeysFile /run/sshd/authorized_keys
UsePAM no
PasswordAuthentication no
KbdInteractiveAuthentication no
ChallengeResponseAuthentication no
PermitRootLogin no
PermitEmptyPasswords no
PubkeyAuthentication yes
PermitUserEnvironment no
AllowTcpForwarding no
X11Forwarding no
PermitTunnel no
PermitTTY no
GatewayPorts no
AllowAgentForwarding no
LogLevel VERBOSE
Subsystem sftp internal-sftp

Match User backup
    ChrootDirectory /home/backup
    ForceCommand internal-sftp
    AllowTcpForwarding no
    X11Forwarding no
    PermitTTY no