Andy's VMware vSphere tip#6: [InstallationError] [Errno 28] No space left on device - updating from 6.5 U1 to 6.5 U2 (possible other versions as well!)
We were updating HPE Proliant Servers Generation 8 [G8], and it would appear as of writing HPE have still not released a Gen8 ESXi 6.5 U2 Image! So we had to use 6.5 U1 and updated to U2. [Please note always use the OEM version of ESXi for vendor servers, e.g. HPE, Dell, IBM/Lenovo, Fujitsu etc]
If after applying VMware vSphere (ESXi) security update - ESXi-6.7.0-20190504001-standard (Build 13644319) - https://kb.vmware.com/s/article/55636 and adding VMkernel.Boot.hyperthreadingMitigation = TRUE After restarting ESXi you notice half the number of logical processors (e.g. hyperthreading disabled!) - this is NORMAL!. "Enabling this option will result in the vSphere UI reporting only a single logical processor per physical core; halving the number of logical processors if Hyperthreading was previously enabled. In addition Hyperthreading may be reported as 'Disabled' in various configuration tabs."
BEFORE UPDATE VMkernel.Boot.hyperthreadingMitigation = false
AFTER UPDATE VMkernel.Boot.hyperthreadingMitigation = true