推荐订阅源

nano /etc/gdm3/greeter.dconf-defaults

banner-message-enable=true
banner-message-text='IP: '

nano /usr/local/bin/update-login-ip

#!/bin/sh
# 取默认路由所在接口
IFACE=$(ip -o -4 route show to default | head -n1 | awk '{print $5}')
[ -z "$IFACE" ] && exit 0
IP=$(ip -4 addr show dev "$IFACE" scope global | awk '/inet /{print $2}' | cut -d/ -f1)
[ -z "$IP" ] && IP="N/A"

# 写回 greeter.dconf-defaults
sed -i "s/^banner-message-text=.*/banner-message-text='IP: ${IP}'/" /etc/gdm3/greeter.dconf-defaults

# 让 dconf 立即读入
dconf update
systemctl restart gdm3

nano /etc/NetworkManager/dispatcher.d/50-login-ip

#!/bin/sh
# $1=接口名 $2=事件
case "$2" in
    up|dhcp4-change|connectivity-change)
        /usr/local/bin/update-login-ip
        ;;
esac