防止 systemd 计时器在按流量计费的连接上运行

Question

我有一个 systemd 计时器，每 10 分钟运行一次，用于下载我的电子邮件offlineimap。问题是我有时会收到大量邮件或大附件，同时我可能正在路上使用我的手机\xe2\x80\x99s 按流量计费的连接。

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现在我有一个自定义脚本，用于查询当前活动的连接nmcli并检查它是否是计量连接。offlineimap如果是这样，它根本不会运行。

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我的问题是，systemd 计时器可以做同样的事情吗？沿着这些思路：

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[Timer]\nOnUnitInactiveSec=10m\nRunOnMetered=no\n

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Answer 1

You first need a Unit to depend upon which indicates whether the connection is or is not metered, like:

[Unit]
Description=Check if the current connection is metered

[Service]
Type=oneshot
ExecStart=check-metered-connection.sh

The check-metered-connection.sh is a simple dbus check:

[Unit]
Description=Check if the current connection is metered

[Service]
Type=oneshot
ExecStart=check-metered-connection.sh

Then your Units would depend on that service and you are good to go, like:

Requires=unmetered-connection.service
After=unmetered-connection.service

Somebody already thought about that and was kind enough to publish the code on Github, see jdorel/systemd-metered-connection-dependency for the full code.

All code samples here are not mine but copied verbatim from the linked repository. Just copied here for completeness.