Set up eth0 network interface using DHCP in initramfs

Question

I created my own initramfs script (based on live-initramfs) and I need set up network connection (using DHCP) to get remote file. So what do I need to add to initramfs hook file (ifconfig, dhclient?). And how to write my initramfs script? Now I am trying something like this:

mkdir -p /var/run/network  # needed by ifup
modprobe af_packet         # for DHCP?
udevadm trigger            
udevadm settle  
ifup eth0                  #???            

for ifup I need /etc/network/interfaces file to have:

auto eth0
iface eth0 inet dhcp

But generally I don't know what exactly need to be done for network device to work properly in initramfs.

Any idea or help?

Answer 1

The simplest solution is to use ipconfig with the ip= option (following the kernel name) in grub.cfg (or pxelinux.cfg or however you boot your kernel). I'm not aware of a man page for it, but you can probably find a README file in /usr/share/doc/klibc-utils. So your grub.cfg might have a line such as the following:

linux   /boot/vmlinuz-3.1.0-1-amd64 root=UUID=someuuid ro quiet ip=:::::eth0:dhcp

Then you can make a simple script in local-top that sources the functions file and then calls the *configure_networking* function such as:

. /scripts/functions
configure_networking

Edit: Had mistakenly thought *configure_networking* was called by default, but it has to be called - either through your own script or one from a package (in my case, from open-iscsi).