bug#64455: shepherd: unable to use redefined system/system* in 0.10.1

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Hello,

I am using happily shepherd since a few years as my init system on

Debian: amd64 (desktop and notebook), armhf (Cubox).

I was using 0.9.1 with guile-3.0.5 and fibers-1.1.1.

I recently tried 0.10.1 with guile-3.0.9 and fibers 1.3.1 and

encountered a problem with using system and system* in my services:

the simple fact to have the symbol system or system* in

/etc/shepherd.scm or included files (even if the command is not

executed) leads to a misbehaving shepherd, more specifically the

shepherd socket disappears; the system boots but with multiple

instances of the launched daemons.

If a system/system* command is executed while booting, shepherd

blocks at the point of its execution.

Example of service causing the failure:

(register-services

 (make <service>

   #:provides '(mytest)

   #:start (lambda args

           (system "touch /tmp/somefile")

           #t)

   ))

The service is not started at boot, I have to do it manually afterwards,

but I never can go there, as the shepherd socket is missing.

I I add at the end of /etc/shepherd.scm:

(system "touch /tmp/somefile")

I have the same problem.

Strangely at build time the test tests/system-star.sh succeeds, and

after I have booted (without refering to a system/system* command) , I

can run:

# export PID=$$; herd eval root "(system \"echo success! >/proc/$PID/fd/1\")"

(in my case, output appears in /var/log/syslog so I need the redirection)

I have read a bit documentation and code to be aware that system and

system* were redefined in shepherd to be non blocking, I suspect the

problem is how this is done.

I would prefer to have new names in shepherd for the redefined

system/system* and keep the old ones intact.

I have a workaround for this problem: replacing system/system* by

helpers I use, like:

(define (system-value command)

  "Return first line of output when calling (system command)"

  (let* ((port (open-input-pipe command))

       (str (read-line port)))

    (close-pipe port)

    str))

but this is a band-aid.