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Subject: [bug#30498] [WIP v2 shepherd] shepherd: If /dev/kmsg is writable,
	use it for logging.
Resent-Message-ID: <handler.30498.B30498.15197231911287@debbugs.gnu.org>
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
References: <20180217122035.1443-1-dannym@scratchpost.org>
	<20180217164835.1178-1-dannym@scratchpost.org>
	<87muzvtyo3.fsf@gnu.org> <20180226233214.6fe40fa3@scratchpost.org>
Date: Tue, 27 Feb 2018 10:19:47 +0100
In-Reply-To: <20180226233214.6fe40fa3@scratchpost.org> (Danny Milosavljevic's
	message of "Mon, 26 Feb 2018 23:32:14 +0100")
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To: Danny Milosavljevic <dannym@scratchpost.org>
Cc: 30498@debbugs.gnu.org

Hi Danny,

Danny Milosavljevic <dannym@scratchpost.org> skribis:

>> As for cryptsetup, what if the service that runs crypsetup simply
>> parameterizes =E2=80=98log-output-port=E2=80=99 to /dev/console?  That w=
ould give us the
>> current behavior, right?
>
> I don't understand why this current-output-port stuff is somehow passed o=
n to
> forked processes in the first place (why does cryptsetup care what I do
> to guile variables?).
>
> scheme@(guile-user)> (current-output-port (%make-void-port "w"))
> scheme@(guile-user)> (system* "ls" "/")
> scheme@(guile-user)>

Funny no?  :-)

This is in libguile/posix.c, =E2=80=98scm_open_process=E2=80=99 and =E2=80=
=98start_child=E2=80=99: when
the current input/output/error port isn=E2=80=99t a file port, FDs 0/1/2 in=
 the
child are made to point to /dev/null.  Otherwise, they are inherited as
file descriptors.

For cryptsetup, this should be what we want if we do:

  (call-with-output-file "/dev/console"
    (lambda (port)
      (parameterize ((log-output-port port)
                     (current-input-port port)
                     (current-error-port port))
        (invoke "cryptsetup" =E2=80=A6))))

Or do we even need to care about =E2=80=98log-output-port=E2=80=99?  Though=
ts?

> It wasn't my intention to inherit them as file descriptors... also, for g=
uile
> buffering ports, how does it inherit those as file descriptors?  Will it =
still
> do the custom line buffering that shepherd does, also when a child process
> writes there?

Shepherd does not process the stdout/err of child processes in any way,
so there shouldn=E2=80=99t be buffering there.

Ludo=E2=80=99.