systemd 的“oneshot"和“simple"服务类型有什么区别? [英] What is the difference between systemd's 'oneshot' and 'simple' service types?

问题描述

systemd 服务 Type oneshot 和 simple 有什么区别?这个链接 声明使用 simple 而不是 oneshot 作为计时器.我无法正确理解.

What is the difference between systemd service Type oneshot and simple? This link states to use simple instead of oneshot for timers. I am not able to understand it correctly.

推荐答案

Type=oneshot 服务单元:

• 在启动操作上阻塞，直到第一个进程退出，其状态将报告为正在激活"；

• blocks on a start operation until the first process exits, and its state will be reported as "activating";

一旦第一个进程退出，就会从激活"直接转换为非活动"，除非设置了 RemainAfterExit=true(在这种情况下，它在没有进程的情况下变为活动"！);

once the first process exits, transitions from "activating" straight to "inactive", unless RemainAfterExit=true is set (in which case it becomes "active" with no processes!);

可能有任意数量(0个或更多)的ExecStart=指令，它们将按顺序执行(等待每个启动的进程退出，然后再启动下一个)；

may have any number (0 or more) of ExecStart= directives which will be executed sequentially (waiting for each started process to exit before starting the next one);

可以省略 ExecStart= 但有 ExecStop=(与 RemainAfterExit=true 一起用于安排事情在系统上运行关机).

may leave out ExecStart= but have ExecStop= (useful together with RemainAfterExit=true for arranging things to run on system shutdown).

Type=simple 服务单元:

• 在启动操作时不会阻塞(即在分叉第一个进程后立即变为活动"状态，即使它仍在初始化！)；

• does not block on a start operation (i. e. becomes "active" immediately after forking off the first process, even if it is still initializing!);

一旦第一个进程退出，就会从活动"转换为非活动"(没有 RemainAfterExit= 选项)；

once the first process exits, transitions from "active" to "inactive" (there is no RemainAfterExit= option);

通常不鼓励使用，因为无法区分由于配置错误而在启动时退出"和运行时 500 毫秒后崩溃"等情况.

is generally discouraged because there is no way to distinguish situations like "exited on start because of a configuration error" from "crashed after 500ms of runtime" and suchlike.

Type=oneshot 和 Type=simple 单位:

• 忽略第一个进程的任何子进程，因此不要将这些模式用于分叉进程(注意:您可以将 Type=oneshot 与 KillMode=none、但只有在您知道自己在做什么的情况下才能这样做).

• ignore any children of the first process, so do not use these modes with forking processes (note: you may use Type=oneshot with KillMode=none, but only do this if you know what you are doing).

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