阿里云Ubuntu登录信息示例
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Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.4.0-81-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
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Last login: Fri Jun 23 13:49:31 2017 from 121.69.23.252
如何自定义展示信息呢？
数据来源
/var/run/motd.dynamic
该目录中存放的是自系统启动以来描述系统信息的文件，标准要求这个文件夹中的文件必须是在系统启动的时候清空，以便建立新的文件。
这就导致了，一个问题，当我修改完成后，再次启动时，修改信息依然无效。修改方式
Ubuntu 与别的 Linux 不同，直接修改 /etc/motd 文件重登录后无效。因为这里 /etc/motd 是一个符号链接，指向 /var/run/motd，应该是一个启动后在生成的文件。
在Ubuntu系统中，找到生成的脚本在目录 /etc/update-motd.d/ 中，那几个有序号的文件就是，包括 00-header，10-help-text , 91-release- upgrade。修改这几个文件，可以得到自己想要的结果。笔者修改demo
# 10-help-text
#!/bin/sh
#
# 10-help-text - print the help text associated with the distro
# Copyright (C) 2009-2010 Canonical Ltd.
#
# Authors: Dustin Kirkland <kirkland@canonical.com>,
# Brian Murray <brian@canonical.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
printf "\n"
printf " * Documentation: https://help.ubuntu.com\n"
printf " * Management: https://landscape.canonical.com\n"
printf " * Support: https://ubuntu.com/advantage\n"
printf "\n"
printf " * 大家好，我是自定义信息:\n"
即时展示
修改后用：sudo run-parts /etc/update-motd.d 去执行就会立即见到效果，而不用反复注销登录。
