As I was fooling around with esxcli in my lab I decided to upgrade a 6.7u3 host to 7.0u1. Note that it is a simple vSphere host in workstation to which I allocated a mere 4GB of RAM because I only needed the minimum. I connected the ISO > upgraded > no problem. Then I went on to patch vSphere 7.0 with esxcli and was greeted with :

Error: Unknown command or namespace software install

Strange. I tried running “esxcli” by itself and got the following output. Wait what?

At this point I’m wondering “How on earth did I manage to screw up the most common vSphere upgrade path ever?”. I looked into vmkernel.log and found truckloads of these records:

2020-11-18T11:35:44.431Z cpu3:68620)UserWorld ‘vim-cmd’ with cmdline ‘/bin/vim-cmd -U root -c /etc/vmware/hostd/config.xml hostsvc/autostartmanager/autostart’

2020-11-18T11:35:44.431Z cpu3:68620)uw.68620 (18832) extraMin/extraFromParent: 256/256, host (0) childEmin/eMinLimit: 1043298/1043298

2020-11-18T11:35:44.431Z cpu3:68620)User: 3201: vim-cmd: wantCoreDump:vim-cmd signal:6 exitCode:0 coredump:disabled

2020-11-18T11:35:47.848Z cpu0:68626)Admission failure in path: host:vim:vmvisor:boot:vim-cmd.68626:uw.68626

2020-11-18T11:35:47.848Z cpu0:68626)UserWorld ‘vim-cmd’ with cmdline ‘/bin/vim-cmd -U root -c /etc/vmware/hostd/config.xml hostsvc/autostartmanager/autostart’

2020-11-18T11:35:47.848Z cpu0:68626)uw.68626 (18877) extraMin/extraFromParent: 50/50, host (0) childEmin/eMinLimit: 1043298/1043298

2020-11-18T11:35:47.848Z cpu0:68626)Admission failure in path: host:vim:vmvisor:boot:vim-cmd.68626:uw.68626

After a quick googling I found KB74527 which is not identical but similar “Admission failure in path: nicmgmtd/nicmgmtd”. The identified cause relates to a lack of memory:

This issue occurs because the process nicmgmtd runs out of memory and is not able to fulfill the requests.

Sure enough, when I changed my ESXi VM from 4GB to 8GB everything was back to normal.

Bottom line: vSphere 7.0 is hungrier than 6.x in terms of memory… Maybe consider this and run some tests before upgrading your production environment to 7.0 if you don’t have much legroom in the resources department.