in file /etc/default/grub variable GRUB_CMDLINE_LINUX

ip=<ipaddress>:<server-address unused for luks>:<gateway>:<netmask>:<hostname>:eth1:static

or for dhcp

ip=:::::eth0:dhcp

in file /etc/mkinitcpio.conf add to hooks netconf dropbear encryptssh

• mkinitcpio-netconf for netconf
• mkinitcpio-utils for encryptssh
• mkinitcpio-dropbear for dropbear