static IP & DHCP problems on LAN

[Tom H]

On Mon, Mar 11, 2013 at 10:26 AM, Adam Funk <a24061 at ducksburg.com> wrote:
>
> I had some trouble with my NAT router the other day, so I was using
> the cable modem (which I normally use in "modem mode", i.e., straight
> through to my own router) for a few hours.  I got everything back to
> normal, but on two consecutive days now, around 01:30 or so, the
> machine (desktop & home "server") has gone off its static IP address
> and onto a DHCP address from the router, which makes it impossible for
> me to SSH into it (unless I can guess the IP address correctly).
>
> When I sit down at it & run
>
> sudo ifdown -a
> sudo ifup -a
>
> it comes up with the correct static address, but then something funny
> happens early in the morning to turn it back to DHCP.  I also tried
> running the '/etc/init.d/networking restart' command today, & that
> screwed up graphics & lightdm to the extent that I rebooted the
> machine in desperation.
>
> Q1. How can that init.d/networking command screw up things unrelated
>     to networking?  I expected it to do little more than 'ifdown -a ;
>     ifup -a'.
>
> Q2. What is allowing something else to override my static config in
>     /etc/network/interfaces in the early morning?  The config file is
>     the same as it was before except for a commented out stanza.

cat /etc/network/interfaces