auto eth0
iface eth0 inet static
address x.x.11.42
netmask 255.255.255.0
gateway x.x.11.1
post-up ip addr add x.x.29.26/24 dev eth0
pre-down ip addr del x.x.29.26/24 dev eth0
сat img_links | xargs -n 1 -P 5 wget {}
if [[ `wget -S --spider http://link_to_image.jpg 2>&1 | grep 'HTTP/1.1 200 OK'` ]]; then
...