On 9/29/2015 10:06 AM, Colin Booth wrote:
Again, the goal (implied, but unstated) here isn't "test to see if
s6-rc works for end-to-end system management" (it definitely does),
the goal is "see how much work/pain in the ass it is to convert a
typical end-user system* to s6-rc." Hence all the hand-wringing about
trying to stick close to a stock Debian and not wanting to modify init
scripts.
Having gone through that pain last year (Debian 7/Debian 8), I could
chip in a few pointers.
1. Dual inits are a pain in terms of maintenance, but they are wonderful
for troubleshooting a new arrangement. Nothing is more frustrating than
trying to get into a machine that won't boot properly, so falling back
to "stock boot" helps a lot.
2. Debian *will* overwrite your boot arrangement if you retain whatever
"stock" init system they are using. It does this for both the old way
(Deb7/SysV) and the new way (Deb8/systemd). The only solutions are to
either be vigilant about what is updated, pin the init system in apt
(which prevents updates to it), or stop using dual-inits (which has its
own issues).
3. Apt-get on 7 will attempt to call init.d scripts unless you disable
them explicitly. I have no clue how to get around this in 8 but I
suspect there's a way to deal with that too. It will continue to do
this even after the init system is stripped out. So each upgrade
becomes an obstacle course with extra steps to deal with.
4. Debian's past discussions have made it fairly clear that while they
will be happy to allow you to have your own init/supervisor arrangement,
they won't lift a finger to support it. I don't follow these
discussions entirely so it may have changed in the last few months. But
this means that the behaviors in (2) and (3) will most likely continue.
5. I think the only way out of this silly situation is the creation of
.debs with your init/supervisor, and include some support scripts in
them to intercept whatever brain damage apt-get seems to be enduring
with regard to restarting daemons after upgrading them. Given the
situation that Gerrit already has runit as a deb /and/ it requires a lot
of hand-holding to integrate the "official" deb into the system, I see
this being a slightly uphill battle for s6.
