First thoughts on s6

From: Steve Litt <>
Date: Tue, 16 Jun 2015 20:44:32 -0400

Hi all,

I have a proof of concept s6 running, *supervision only*, on a Plop
Linux VM. It is started by sysvinit (inittab), and supervises tty5 just
fine, including logging (which is how I found out my run command
originally had bad syntax).

Here are some first impressions...

Plop Linux has one of those /dev/random generators that just stops
after a few characters. This caused the ./configure on skalibs to lock
up while checking for /dev/random (thank you very much for the clear
messages). In fact, /dev/random on this VM locks up dd too. I
strongarmed the problem by removing /dev/random and making a hard link
called /dev/random to /dev/urandom. What the heck, it's an experimental
VM I can throw away, so any side effects this caused probably won't
cause me a whole lot of trouble.

I'd suggest a ./configure option called --urandom-instead, because this
isn't the first time I've seen a /dev/random act like this, and
probably most people don't want to pull the strongarm I did (I wouldn't
either if it were a real machine).

My tty5 takes 1 second from Ctrl+D til the time the next login prompt
is printed. Is this a feature, or a bug?

The following two commands worked *very* differently:

* cat /service/tty5/log/main/current | tai64nlocal

* cat /service/tty5/log/main/current | tai64n

The former command worked as expected and printed out yyyy/mm/dd plus
time timestamps. The latter command appeared to print out two different
tai64n timestamps, both fairly close to each other but different.

I think the following additions would make the s6 website a lot easier
to use, and a lot easier for somebody to begin using s6:

* A page with simple files, including run and log/run for a tty.

Here are the run files I used for tty5:

For the service:

exec 2>&1
echo Starting tty5 >&2
exec /sbin/getty tty5

For the tty5 log:
exec s6-log t ./main

They seemed to work well. Anyway, so far so good.



Steve Litt
June 2015 featured book: The Key to Everyday Excellence
Received on Wed Jun 17 2015 - 00:44:32 UTC

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