apt-get update 命令运行时候出现错误
If these errors aren’t fixed, apt will have problems when installing or upgrading packages.
The apt packaging system has a set of trusted keys that determine whether a package can be authenticated and therefore trusted to be installed on the system. Sometimes the system does not have all the keys it needs and runs into this issue. Fortunately, there is a quick fix. Each key that is listed as missing needs to be added to the apt key manager so that it can authenticate the packages.
Looking at the error above, apt is telling us that the following keys are missing:
. Notice that these are listed multiple times. Each unique key will only need to be added once.
To add these keys, run the following commands:
sudo apt-key adv –keyserver keyserver.ubuntu.com –recv-keys 7EA0A9C3F273FCD8