Reduce ESXi OS partition size

When installing ESXi 7.0u2 to an internal SSD of 120GB, I noticed the system allocated all available storage as Virtual Flash. This leaves no space for a datastore, thus no local datastore is created. Pretty annoying, because this means you cannot have local VMs if you don’t install a second drive.

The good thing is, we can limit the OS partition size. The bad thing is, we can only do this at installation time. (Another bad thing, this is unsupported, but that’s not really an issue in a lab environment.)

How do we go about it?
Boot to the installer, at the ESXi boot screen press crtl+o to append additional setup parameters. The parameter you are looking for to set a custom size (example is 8GB) is:

According to KB81166, there also are other (more supported options):

  • Set the “minimal” size (33GB):
  • Set the “small” size (69GB):
  • Set the “max” size (uses all space available):

Keep in mind, YMMV, and please keep the original (supported) default values when working in production environments.