前阵子才搭的树莓派博客，时不时会遇到无法访问的问题，但是等一下下又会恢复正常，VNC上去，发现系统并没有重启，所以怀疑是网络的问题。这几天趁有空，研究了一下，果然是无线网卡power management搞的鬼。

首先，在terminal中执行journalctl --since=yesterday，然后寻找是否有wlan0: carrier lost的条目。如果有的话，那恭喜你，罪魁祸首就是power management。

要禁用power management，首先确认当前是开启的，执行sudo iw wlan0 get power_save，确认返回结果是Power save: on

接下来，执行sudo nano /etc/rc.local，将以下代码添加到exit 0之前：

/sbin/iw dev wlan0 set power_save off

问题就此解决。

What is an E-6?

The Boeing E-6 Mercury (formerly E-6 Hermes) is an airborne command post and communications relay based on the Boeing 707. The original E-6A manufactured by Boeing’s defense division entered service with the United States Navy in July 1989, replacing the EC-130Q. This platform, now modified to the E-6B standard, conveys instructions from the National Command Authority to fleet ballistic missile submarines (see communication with submarines), a mission known as TACAMO (“Take Charge And Move Out”). The E-6B model deployed in October 1998 also has the ability to remotely control Minuteman ICBMs using the Airborne Launch Control System. The E-6B replaced Air Force EC-135Cs in the “Looking Glass” role, providing command and control of U.S. nuclear forces should ground-based control become inoperable. With production lasting until 1991, the E-6 was the final new derivative of the Boeing 707 to be built.^[2]