Overview
How to customize the partition sized during OpenBSD installation to give /var more space.
Edit Auto Configured Disk Layout
At install time you can choose (A) for auto-layout. This creates a lot more partitions than other distributions. Often times it gives more space to /home than I'd like especially if the installation is going to be a server. </br> Fortunately you can (E) edit the auto-layout. When you press (E) you get dropped to a fdisk like command prompt. </br> Here are some helpful commands"
? Help a Add partition d Delete partition p Print partition table z Delete all partitions
The default partition layout looks like this:
a: / b: swap c: reserved/unused d: /tmp e: /var f: /usr g: /usr/X11R6 h: /usr/local i: /usr/src j: /usr/obj k: /home
On servers that won't host many users I prefer to make /var the last partition so I can have it use 100% of the remaining space. You can do this by specifying 100& for the partition size.
Reference
https://dev.to/nabbisen/openbsd-manual-partitioning-at-installation-4cif