Have a look at this excellent comparison for supervisor / init tools:

http://skarnet.org/software/s6/why.html

S6 is the bees' knees

On 28 March 2015 at 01:32, Steve Litt <slitt@???> wrote:

> Hi all,
>
> I'm managing more and more of my daemons with daemontools. This is
> currently happening on my sysvinit-initted Wheezy, but I think I'll do
> it forever. By the way, anything good I say about daemontools goes
> even more so for Bruce Gunter's daemontools-encore.
>
> I could have managed my daemons with sysvinit, using the respawn, and a
> lot of people ask me "what's the point of the extra software
> (daemontools) when it's already doable from your init system?"
>
> Here's why:
>
> * Daemontools has a rich set of tools to start, stop, and restart your
> daemons.
> * Daemontools has built-in logging that captures everything from the
> daemon's stdout (stderr too if you want).
> * Daemontools' svstat command gives you the daemon's PID: No guessing,
> no .pid files, no parsing ps ax.
> * Daemontools is ultra-reliable.
> * Daemontools is dead bang simple, constructed purely from Unix
> constructs. It's completely understandable.
> * Daemontools can be made to run at the end of a boot, thereby removing
> complexity from the init itself.
> * If you can devise a test to show that a required service is running
> correctly, you can implement service dependencies reliably with
> Daemontools.
> * Daemontools can take any old shellscript or Python/Perl/Ruby/Lua
> program you write and turn it into an always starts, reliably managed
> daemon, with logging. Daemontools is the easy way to deploy DIY
> daemons.
> * A deep understanding of daemontools, which is not hard to achieve,
> gives you a big head start on understanding actual init programs.
> * Daemontools gives you much better ways to declare that daemons run or
> don't run than lame, number-in-comments symlinks to five function
> init scripts.
> * Daemontools init scripts are pretty much all the same, are short and
> easy to understand. Contrast this to sysvinit, systemd, OpenRC or
> Upstart.
>
> The following is my daemontools run script for ntpd. Note that it
> enforces a dependency that the network be up before it starts:
>
> ==================================================
> #!/bin/sh
>
> ######## DON'T START ntpd UNTIL THE NETWORK'S UP #######
> pingaddr=8.8.8.8
> #pingaddr=8.8.8.86 # for testing unpingable IP address
> echo "Starting Litts ntpd daemon"
> echo "Litts ntpd daemon checking network"
> if ! ping -q -c1 $pingaddr > /dev/null; then
> echo failed ping test on $pingaddr
> sleep 3
> echo "Bailing til next time"
> exit 1
> fi
>
> ####### RUN THE DAEMON #######
> echo ping test succeeded, starting ntpd
> exec 2>&1
> echo About to start ntpd
> exec /usr/sbin/ntpd -d -s
>
> ==================================================
>
> For the guy who has memorized all of systemd's init keywords, this is a
> little bit more complicated than the equivalent systemd unit file. Foor
> the guy who hasn't memorized systemd's unit file keywords, this is much
> easier and more intuitive. Anyone with a bit of Unix knowledge and the
> understanding that a daemontools run script that terminates gets
> restarted by supervise in 1 to 5 seconds instantly understands what
> this script is doing, and can write it from his/her knowledge.
>
> In my opinion, no matter what init system you're running, daemontools
> or daemontools-encore is a great addition to make your system more
> understandable and maintainable.
>
> SteveT
>

> Steve Litt                *  http://www.troubleshooters.com/
> Troubleshooting Training  *  Human Performance

>
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