<p dir="ltr">Partial answer:</p>
<p dir="ltr">On Dec 5, 2013 8:40 AM, "Cecil Westerhof" <<a href="mailto:Cecil.Westerhof@snow.nl">Cecil.Westerhof@snow.nl</a>> wrote:<br>
><br>
> Today I am giving my presentation about systemd/journald for a not very enthusiastic public. I would like some last answers on a ‘few’ questions.<br>
><br>
> I understood that you could let systemd start-up the services sequential for debugging purposes. How is that done?<br>
><br>
> Is it possible to change the limits dynamically? When I change the service files and do a reload, are the new limits used, without a reboot being needed?<br>
><br>
> One of the problems mentioned is that services can be started only when they are used for the first time. As I understood it, you can make sure that a service is always loaded, so that there is no waiting time the first time it is called.</p>
<p dir="ltr">This is not a problem. This is a configuration choice. If the service supports activation, you *can* let it be activated if that suits you, but you can also configure it to be started on boot as any other service (i.e. make multi-user.target depend on the service directly).</p>
<p dir="ltr">Note that activation benefits even boot-started services, because their sockets still become available very early, while the service's startup is still pending. Various existing services already run this way - e.g. dbus.service always starts on boot, but it is *also* activated, so all other programs can connect to it without a failure and the kernel will queue up connections.</p>
<p dir="ltr">Also note that this is not new in systemd. DBus has always worked this way - if program X sends a message to DBus service Y, dbus-daemon starts Y on demand.</p>
<p dir="ltr">><br>
> I understood you could deny a service network connection. How is this done? Until no I could not find it. Is it possible to limit the bandwidth a service is allowed to use?</p>
<p dir="ltr">PrivateNetwork=yes will create a dedicated net namespace for that service, which does not have any network interfaces by default. (Relevant man pages: clone, unshare, setns, nsenter; LXC also uses this.)</p>
<p dir="ltr">><br>
> When virtual machines are implementd as a service. You need to let the host define the limits per guest I suppose?<br>
><br>
> How do you let a block-device be read-only for a service?<br>
><br>
> Any last tips about what to share?<br>
><br>
> -- <br>
><br>
> Cecil Westerhof<br>
> Snow B.V.<br>
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</p>