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| author | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-05 22:26:11 +0000 |
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| committer | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-05 22:26:11 +0000 |
| commit | 90b12bd71bb9fc79a4640b9112c13ef529d0196a (patch) | |
| tree | 523b3f4ee2969e7a729bab2ba749c4b924ae62af /doc/s6-svscan-not-1.html | |
| download | s6-90b12bd71bb9fc79a4640b9112c13ef529d0196a.tar.xz | |
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diff --git a/doc/s6-svscan-not-1.html b/doc/s6-svscan-not-1.html new file mode 100644 index 0000000..613ba3d --- /dev/null +++ b/doc/s6-svscan-not-1.html @@ -0,0 +1,140 @@ +<html> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>s6: How to run s6-svscan under another init process</title> + <meta name="Description" content="s6: s6-svscan as not-init" /> + <meta name="Keywords" content="s6 supervision svscan s6-svscan init process boot" /> + <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> --> + </head> +<body> + +<p> +<a href="index.html">s6</a><br /> +<a href="http://skarnet.org/software/">Software</a><br /> +<a href="http://skarnet.org/">skarnet.org</a> +</p> + +<h1> How to run s6-svscan under another init process </h1> + +<p> + You can have a reliable supervision tree even if s6-svscan is not your process 1. +The supervision tree just has to be <em>rooted</em> in process 1: that means that +your process 1 will have to supervise your s6-svscan process somehow. That way, +if s6-svscan dies, it will be restarted, and your set of services will always +be maintained. +</p> + +<p> + Be aware, though, that pipes between services and loggers are maintained +by the s6-svscan process; if this process dies, the pipes will be closed and +some logs may be lost. +</p> + +<a name="log"> +<h2> Logging the supervision tree's output </h2> +</a> + +<p> + s6-svscan and the various s6-supervise processes might produce error or +warning messages; those messages are written to s6-svscan's stderr (which +is inherited by the s6-supervise processes). To log these messages: +</p> + +<ul> + <li> You can use your init system's logging tools, and make your init +system launch s6-svscan as is; its stderr should already be taken care +of by the logging tools. </li> + <li> You can use a trick similar to the <a href="s6-svscan-1.html#log">process +1 output logging trick</a> so the supervision tree's messages are logged via +a service that's maintained by the supervision tree itself. Then your init +system should not launch s6-svscan directly, but a wrapper script that performs +the proper redirections. The +<tt>examples/s6-svscanboot</tt> file in the s6 distribution gives an example of +such a script. Make sure that your initial <a href="scandir.html">scan +directory</a> contains a <a href="servicedir.html">service directory</a> for your +initial logging service, that must read on the logging FIFO. </li> +</ul> + +<p> + In the following examples, we'll assume that <tt>/command/s6-svscanboot</tt> +is the name of the script you are using to start s6-svscan. Adjust this accordingly. +</p> + +<a name="sysv"> +<h2> System V init </h2> +</a> + +<p> + Put an appropriate line in your <tt>/etc/inittab</tt> file, then reload this +config file with <tt>telinit q</tt>. +</p> + +<h3> Example </h3> + +<pre> SV:123456:respawn:/command/s6-svscanboot </pre> + + +<a name="upstart"> +<h2> Upstart </h2> +</a> + +<p> + Put an appropriate configuration file in the <tt>/etc/init</tt> folder, +for instance <tt>/etc/init/s6-svscan.conf</tt>, then start the service +with <tt>start s6-svscan</tt>. +</p> + +<h3>Example </h3> + +<pre># s6-svscan +start on runlevel [2345] +stop on runlevel [!2345] + +oom never +respawn +exec /command/s6-svscanboot +</pre> + +<a name="systemd"> +<h2> systemd </h2> + +<p> + systemd has +<a href="http://www.freedesktop.org/software/systemd/man/daemon.html">its +own way</a> of supervising services. If you are a systemd user, chances +are you do not need s6. If you are interested in using s6, I encourage +you to also stop using systemd. +</p> + +<p> + +</p> + +<a name="bsd"> +<h2> BSD init </h2> +</a> + +<p> + Put an appropriate line in your <tt>/etc/ttys</tt> file, then reload this +file with <tt>kill -s HUP 1</tt>. +</p> + +<h3> Example </h3> + +<pre> sv /command/s6-svscanboot "" on </pre> + +<a name="launchd"> +<h2> MacOS X launchd </h2> +</a> + +<p> + Like systemd, launchd comes with its own +<a href="https://developer.apple.com/library/mac/documentation/macosx/conceptual/bpsystemstartup/chapters/CreatingLaunchdJobs.html">way +of supervising services</a>; if you are a launchd user, you probably do +not need s6. +</p> + + +</body> +</html> |