[SOLVED] Dynamically generating /etc/network/interfaces file every time ifupdown is run

D1ver · 03-12-2014, 02:06 AM

Hello,

I'm working on an embedded Linux project and I'm having a little problem trying to handle user-configurable interface settings. The device is running emdebian and networking is handled by ifupdown.

The goal is to have a website where a user can chose either DCHP mode or static mode, and configure the static IP, gateway, netmask etc.

I've set up the following /etc/network/interfaces file

Code:

auto lo
iface lo inet loopback 

auto eth0
iface eth0 inet static
        address $(/root/ethernet.sh address)
        gateway $(/root/ethernet.sh gateway)
        netmask $(/root/ethernet.sh mask)

Where /root/ethernet.sh is a script that returns the user configured parameters (EG. '/root/ethernet.sh address' returns 10.10.6.100).

This configuration works fine. However if I try to expand it to include the option for DHCP it doens't seem like I'm able to dynamically generate the 'iface eth0 inet static' line. For example if I use the following

Code:

auto eth0
$(echo "iface eth0 inet static")

ifup complains about misplaced options.

If I try

Code:

 
$(echo -e "auto eth0 \n iface eth0 inet static")

ifup complains about unknown interface eth0.

Anyone have any ideas? I'm also open to better ways to do this..

nikmit · 03-12-2014, 10:05 AM

This might be rather obvious, but why don't you directly adjust the content of /etc/network/interfaces and then run ifupdown?

When your user submits the web form containing the settings, your CGI should create a new interfaces file with the supplied information and then apply them by restarting networking.

D1ver · 03-12-2014, 07:11 PM

Can't see the forest for the trees sometimes I guess.

I didn't really consider regenerating the whole interfaces file because I wanted ifupdown to trigger the system to go fetch the configurable data, but if I can ensure that the interfaces file is updated correctly whenever the user submits changes then I guess that will work fine.

Cool, cheers.