This is only really necessary in the case you don't want DHCP. If you are dealing with an encrypted LUKS server on the internet, you will often want to have a static IP so you know which IP to connect to (or if you have a semi-static IP assigned by DHCP).
SET IP Address by /etc/initramfs-tools/initramfs.conf
Subnet Mask: 255.255.255.0
The format is below, note the "double colon" :: after the IP. If you don't do that, things won't work properly including being unable to set the gateway and/or hostname errors.
**Double note that the kernel documentation states otherwise that a single color is to be used for all field separation, but at least in most newer Debian's this does not work.
Set IP for certain NIC
You could also add another ":" after hostname which would indicate which NIC device the IP would be applied to. Otherwise by default it is the first NIC.
#eg if you wanted to have it use ens3 then change the line by adding another colon and the device eg. :ens3
Follow this guide if you want your NICs named properly (eg. eth0, eth1) so you don't have to wonder whether you have an eno1, ens3 etc.
Make sure you update initramfs or this will not be applied or work until you do.
sudo update-initramfs -u
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