Ok, ça marche, merci beaucoup.
Je mets mon script ici, à tout hasard :
#!/bin/sh
rm /etc/resolv.conf
echo "nameserver 208.67.222.222" >> /etc/resolv.conf
echo "nameserver 208.67.220.220" >> /etc/resolv.conf
echo "nameserver 192.168.1.1" >> /etc/resolv.conf