Question about s6 on Stack Exchange

2020-10-06 Thread Jonathan de Boyne Pollard
Anyone who enjoys explaining s6-rc might enjoy answering 
https://unix.stackexchange.com/q/613225/5132 .


Answers go in the box under "Your Answer", of course.  (-:



Re: s6-rc : Anomalies or normal behaviour

2020-10-06 Thread Laurent Bercot



 Glad it's working for you!



A significant reduction in complexity.  However, and the reason for my
delay in replying.  Magic happened!  I was now transmitting data which
crossed jail barriers (from b3 "named" to b2 "named logging").  I needed
to consult with one of the FreeBSD developers to ensure that a security
hole wasn't occurring. :)


 Well, that's also what you were doing with your former
b3:named2 and b3:named-log2, except you were transmitting the data via
a named pipe created in your run script explicitly instead of an
anonymous pipe created by s6-rc implicitly. The integrated pipe
feature does not touch your security model at all; if you were to
consult with a FreeBSD developer, you needed to do it before making
the change. :)



It appears (and I'm assuming) that s6 uses pseudo terminal sub-system to
communicate. In this specific case below, per pts/3


 No, s6 does not use pseudo-terminals at all; all it does is let
processes inherit fds from their parent. In your case, /dev/pts/3 seems
to be s6-svscan's stdout and stderr; if you don't want to have
pseudo-terminals, you should check the script that launches your
supervision tree, and redirect s6-svscan's outputs accordingly.

--
 Laurent