The manpage for dhclient-script says:
Before actually configuring the address, dhclient-script should
somehow ARP for it and exit with a nonzero status if it receives a
reply.
By using arping in dracut this is very easy, since arping has a
specific option to do just that.
The usual approach to setting mtus is to set the interface down,
set the mtu then set the interface back up again. Modern hardware
and/or drivers may support setting this on the fly, so we try
this and fall back to the old behaviour it it doesn't work.
In addition this patch only allows mtus greater than 576, this is
taken from debian/ubuntu dhclient-script.
The Bug causing dhclient to recall BIND has been identified:
dhclient-script runs with #!/bin/sh -e, causing setup_interface
to fail if no hostname is provided by dhcp as it is the last statement
in that function.
Instead of configuring devices when they are ready, ifup and
dhclient-script write script files which are then sourced by
netroot.
This solves the problem of having multiple interfaces and not knowing
which one to use for dhcp or default route. This way, netroot (which
is serialized anyway) configures the interface before calling the root
handler and deconfigures it if the handler failed.
Example: root=nfs:server:path and ip=dhcp with eth0 and eth1 receiving
a dhcp reply, but eth0 is the correct one to use.
Assuming eth1 is the first to receive the dhcp-reply, netroot starts
and configures eth1. nfsroot is run but fails, so eth1 is deconfigured. If
eth0 has received a dhcp-reply (or not, then we wait) the other locked
netroot process starts and tries with eth0 and succeeds.
Multiline conditionals ( && { ... } ) should use if, function
declarations go to the top of the file, add/update comments and remove
some unnecessary clutter.
This changes the network config to run dhclient from within udev, and
allows multiple dhclients to run at once. It also sets the hostname and
adds a kernel command line option 'netdebug' to help debug network issues.
All modules now live in a subdirectory /modules.d. Each module is
self-contained -- it should contain everything that it will install
on the initrd. All modules must include a script named install, which
will be sourced by dracut. This script should do the actual file installation
using inst methods. The moddir variable will point to the full path to the
module dracut is currently working on.
As usual, this patch series applies on top of my previous patch series,
and is available as normalize-modules from http://git.fnordovax.org/dracut.
Harald Hoyer