[arch-releng] [RFC] [archiso] Use a pure systemd enviroment

[Dave Reisner]

On Wed, Aug 22, 2012 at 11:55:02AM +0200, Thomas Bächler wrote:
> Am 19.08.2012 21:15, schrieb Gerardo Exequiel Pozzi:
> > 1) DHCP is requested again on real-root. I guess, is most cases, there
> > is no issues since is re-assigned the same IP address. (this bug
> > introduced recently since rc.conf enabled "network")
> 
> This is actually necessary. If you don't start a real DHCP daemon on
> boot, then you won't renew your lease and the DHCP server may give the
> IP to someone else.
> 
> Your lease should still be valid when you re-launch DHCP, so you can
> rely on getting the same IP. You could probably even configure dhcpcd to
> specifically request the correct IP.
> 
> > Solutions:
> > a) If this happens suggest the to the user use copytoram=y
> > b) Use copytoram=y in NBD/NFS by default (this is always done for HTTP),
> > user can change this behaviour.
> > c) Disable DHCP service from relevant hooks.
> 
> None of these are good solutions.
> 
> > 2) Stopping network on shutdown, if network is stopped before reach
> > shutdown-initramfs againt this does not look good.
> > Solutions:
> > a) See how to skip network on shutdown.
> > b) Same point (1.b)
> 
> We must not stop network on shutdown. We can quit dhcpcd without
> releasing the lease or shutting down the network. If this is not
> possible with systemd, then something is very wrong.
> 

Both are feasible. Adding the -p flag to dhcpcd to prevent it from
ditching the address on exit is easily done. Alternatively, you can
arbitrarily change argv[0] by prefixing the binary path for ExecStart
with a @, e.g.:

  ExecStart=@/usr/bin/dhcpcd @dhcpcd -A eth0

The @ prefix on the argv0 then tells systemd to not kill this horribly
on shutdown (or should, in theory).

d