Random Musings

For the record, the fact that Debian’s startup tends to fail in the presence of smart switches that try to do spanning-tree detection gets really annoying when you have production machines that depend on NFS servers being available.

Technically, this would be solvable by building a proper hosts file on each server, but that’s what DNS is for.

So, I’m going to try a script like this on each server during the startup sequence, to try to delay the startup until the default gateway comes up:

#!/bin/bash -e

found_addr=0
loop_count=0

gw=$(/bin/netstat -rn | awk ‘/^0.0.0.0/{print $2}’)
echo “Gateway is $gw”
echo “Waiting for $gw to appear in the arp table.”

while [ $found_addr -eq 0 ]; do
echo “Triggering arp lookup with a single ping”
/bin/ping -c 1 -q $gw >/dev/null || true
info=$(/usr/sbin/arp -n $gw | grep “^$gw”)
addr=$(echo “$info” | awk ‘{print $1}’)
hwtype=$(echo “$info” | awk ‘{print $2}’)
echo “hwtype = $hwtype, addr = $addr”
if [ “$hwtype” = “ether” ]; then
found_addr=1
fi

loop_count=$(expr $loop_count + 1)
if [ $loop_count -gt 120 ];
then
echo “120 passes through the loop and nothing happening.”
echo “Giving up and moving on.”
exit 0
fi

if [ $found_addr -eq 0 ]; then
sleep 1
fi
done