自从最近升级到 20.04 以来，我在运行apt update类似于以下内容后看到信息性消息
46 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
31 standard security updates
谷歌搜索未能找到该短语的定义standard security update。它是什么？还有，有吗non-standard security updates？有哪些可能性？
今天在我的服务器目录中做了一些简单的阅读/var/log/，发现了一些我不熟悉的日志 - ubuntu-advantage.log。
日志有类似这样的重复内容
2021-08-01 03:25:21,947 - ua_update_messaging.py:(347) [DEBUG]: Updating UA messages for APT and MOTD.
2021-08-01 03:25:21,947 - util.py:(419) [DEBUG]: Reading file: /etc/os-release
2021-08-01 03:25:21,994 - util.py:(419) [DEBUG]: Reading file: /var/lib/ubuntu-advantage/private/machine-token.json
2021-08-01 03:25:21,994 - config.py:(442) [DEBUG]: File does not exist: /var/lib/ubuntu-advantage/private/machine-token.json
2021-08-01 03:25:22,008 - util.py:(419) [DEBUG]: Reading file: /var/lib/ubuntu-advantage/private/machine-token.json
2021-08-01 03:25:22,009 - config.py:(442) [DEBUG]: File does not exist: /var/lib/ubuntu-advantage/private/machine-token.json
2021-08-01 15:34:22,023 - ua_update_messaging.py:(347) [DEBUG]: Updating UA messages for APT and MOTD.
2021-08-01 15:34:22,036 - util.py:(419) [DEBUG]: …