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| -rw-r--r-- | doc/servicedir.html | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/doc/servicedir.html b/doc/servicedir.html index 7c5d613..044406e 100644 --- a/doc/servicedir.html +++ b/doc/servicedir.html @@ -51,15 +51,28 @@ every time the service must be started, i.e. normally when the service goes down when it is supposed to be up. A run script should normally: <ul> - <li> adjust redirections for stdin, stdout and stderr. For instance, -if your service is logged, the run script should make sure that its -stderr goes into the log pipe (which is on stdout by default), which + <li> adjust redirections for stdin, stdout and stderr. When a run +script starts, it inherits its standard file descriptors from +<a href="s6-supervise.html">s6-supervise</a>, which itself inherits them from +<a href="s6-svscan.html">s6-svscan</a>. stdin is normally <tt>/dev/null</tt>. +If s6-svscan was launched by another init system, stdout and stderr likely +point to that init system's default log (or <tt>/dev/null</tt> in the case +of sysvinit). If s6-svscan is running as pid 1 via the help of software like +<a href="//skarnet.org/software/s6-linux-init/">s6-linux-init</a>, then its +stdout and stderr point to a <em>catch-all logger</em>, which catches and +logs any output of the supervision tree that has not been caught by a +dedicated logger. If the defaults provided by your installation are not +suitable for your run script, then your run script should perform the proper +redirections before executing into the final daemon. For instance, dedicated +logging mechanisms, such as the <tt>log</tt> subdirectory (see below) or the +<a href="//skarnet.org/software/s6-rc/">s6-rc</a> pipeline feature, pipe your +run script's <em>stdout</em> to the logging service, but chances are you want +to log <em>stderr</em> as well, so the run script should make sure that its +stderr goes into the log pipe. This is achieved by <tt><a href="//skarnet.org/software/execline/fdmove.html">fdmove</a> -c 2 1</tt> in <a href="//skarnet.org/software/execline/">execline</a>, and <tt>exec 2>&1</tt> in <a href="http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sh.html">shell</a>. -By default, in a normal supervision tree situation, a run script's stdin will -be <tt>/dev/null</tt>, and its stdout and stderr will both be a pipe to a -catch-all logging program. </li> + </li> <li> adjust the environment for your <em>foo</em> daemon. Normally the run script inherits its environment from <a href="s6-supervise.html">s6-supervise</a>, which normally inherits its environment from <a href="s6-svscan.html">s6-svscan</a>, |