From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 18987 invoked from network); 25 Aug 2021 08:06:56 -0000 Received: from alyss.skarnet.org (95.142.172.232) by inbox.vuxu.org with ESMTPUTF8; 25 Aug 2021 08:06:56 -0000 Received: (qmail 5517 invoked by uid 89); 25 Aug 2021 08:06:46 -0000 Mailing-List: contact supervision-help@list.skarnet.org; run by ezmlm Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Received: (qmail 5510 invoked from network); 25 Aug 2021 08:06:46 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=umbrellix.net; s=umbrellix.net; t=1629878775; bh=L6CPjzFq7yaa7VH0yTHCHEA6839ikjRjFDz3sQdPHeg=; h=Date:From:To:Subject; b=o2QhSdK2W9YJiZkTaccIAeWQTdLO3IKpxzw9i8K4csmcBS9S76IsRBHOOuKmD0Zut dhcZQXtn0p1uKMcRZMvnmYyPGaAwH2fM08fJB7hlY9HmuxWTwSCtZySwdVkV5FJznO WCpJfJWLgl6BdXQHsPaljIAq2VIUYyxdgAoWPriM= Date: Wed, 25 Aug 2021 01:06:14 -0700 (PDT) From: Ellenor Malik Message-Id: <202108250806.17P86E1p031259@invictus.WA.US.Umbrellix.NET> To: supervision@list.skarnet.org Subject: First time caller to the show - am I understanding the fifo trick correctly? Hi supervision@! I realise this is probably more of a skaware@ question as it makes extensive reference to execline and s6-l-i, but I've been perusing the source code of the latter, hoping that I could learn what "the fifo trick" actually was (I have to admit, I've also been perusing skarnet.org/software) and I think I now get it. In case the fifo doesn't exist, the stage 1 initializer (since I won't be using s6-l-i as I'm not on Linux) has to create the fifo that $LOGGERSERVICE reads (see note [loggerservice-runscript] later in this email), then, let's call that fifo $LOGGERSERVICE/fifo, that initializer has to exec into (execline) redirfd -w -n -b 1 $LOGGERSERVICE/fifo s6-svscan. This is so technically nonsensical that I should probably be barred from ever using a computer again, but please stick with me here. That svscan invocation (or any other service supervisor that doesn't mind SIGPIPE) would then initiate supervision of [loggerservice-runscript] and the knot would be untangled. [loggerservice-runscript] #!/package/admin/execline/command/execlineb /package/admin/execline/command/redirfd -r 0 $LOGGERSERVICE/fifo s6-log n10 s10485760 T !"gzip -nq9" $LOGDIRECTORY/s6-svscan # obviously one does not simply use $variables in a runscript - these'd be replaced by the absolute paths at compile time. Forgiving privilege separation failures and minor grammatical mistakes, does it look as if I understand the fifo trick's application in practice? Thanks a lot, -- Ellenor Bjornsdottir (she) sysadmin umbrellix.net aspiring OS integrator