Bug 90505

Summary:	RFE: Singleton Template
Product:	systemd	Reporter:	Sah Lee <contact>
Component:	general	Assignee:	systemd-bugs
Status:	RESOLVED WONTFIX	QA Contact:	systemd-bugs
Severity:	normal
Priority:	medium
Version:	unspecified
Hardware:	All
OS:	Linux (All)
URL:	http://stackoverflow.com/questions/30208805/systemd-how-to-write-a-singleton-unit-template
Whiteboard:
i915 platform:		i915 features:

Description Sah Lee 2015-05-18 10:23:33 UTC

Systemd must provide an option in Unit configuration to indicate a template to be singleton.

There are use cases where a template should have only one instance at a time, and whenever it is instantiated, the existing instance must be stopped first.

My own case is described in this question on Stackoverflow:
http://stackoverflow.com/questions/30208805/systemd-how-to-write-a-singleton-unit-template

Comment 1 Lennart Poettering 2015-05-18 16:21:24 UTC

Hmm? I am not sure I get what you want:

templates and instances are concepts we introduced to allow multiple instances of services, and they only exist for that reason. Before we had them, every unit was a singleton. Hence: if you want a singleton, then simply use a non-template/non-instance unit and all should be good.

Comment 2 Sah Lee 2015-06-08 23:26:37 UTC

Thanks for replying @Lennart .

I am using Systemd to maintain a set of network adaptation scripts, meaning, for instance, to mount samba drives and switch to a certain proxy when I am in office, and to switch to my own proxy (that can bypass the Great Firewall of China) when I am in Starbucks, etc..

To group all the service units, I created a template: `network@.target`, and have several instances such as `network@office.target`, `network@home.target`, `network@starbucks.target`, `network@offline.target`, etc..

Now due to the nature of these targets, there should always be only one instance that is active. But I can't find a way to define this exclusiveness.

Comment 3 Zbigniew Jedrzejewski-Szmek 2018-03-09 08:00:46 UTC

Closing all stale bugs with NEEDINFO. Please open a new bug at https://github.com/systemd/issues if the problem still occurs.

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