最近发现，系统时区会莫名其妙的变成美国时区，但之前显然已经做了时区变更及时间同步任务，检查日志后发现如下信息：
Jan 3 06:39:19 s1 systemd[1]: Starting Daily apt upgrade and clean activities... Jan 3 06:39:39 s1 systemd[1]: Started Daily apt upgrade and clean activities.
原来是Ubuntu默认的开启着自动更新，所以需要做关闭：
apt-get remove unattended-upgrades systemctl kill --kill-who=all apt-daily.service systemctl stop apt-daily.timer systemctl disable apt-daily.timer systemctl stop apt-daily.service systemctl disable apt-daily.service systemctl mask apt-daily.service systemctl daemon-reload
关闭完成后检查结果：
systemctl status apt-daily.timer
注意结果中的：
Active: inactive (dead)
完。