When I tried to upgrade my lab environment from vCenter 6.0 with external PSC to vCenter 5.5, I ran in to an annoying issue. I tried to upgrade my PSC, but the installer was not able to determine the version from my current PSC. It assumed it was 5.5 and I had to confirm this, which of course, I did not. No way to tell it it was really 6.0 …
After trying some stuff I found a log file which showed:
2016-11-15T20:47:38.547Z - error: vimService creation failed: Error: Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http20NamedPipeServiceSpecE:0x7fe24005a890] _serverNamespace = / _isRedirect = false _pipeName =/var/run/vmware/vpxd-webserver-pipe) 2016-11-15T20:47:38.549Z - error: Login failed for source VC (Not found for PSC): Error: Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http20NamedPipeServiceSpecE:0x7fe24005a890] _serverNamespace = / _isRedirect = false _pipeName =/var/run/vmware/vpxd-webserver-pipe)
But I was 100% sure I did use the correct root password for the PSC
Googeling did not show the exact cause for this problem, but since I had seen issues before with expired passwords on the VCSA, I logged in to the PSC with the root account, which did work … So I decided to change the root password …
After changing the root password, I was able to upgrade the PSC 🙂
So most likely changing the root password “unexpired” the password. So the expiration for the linux password is not the same as the expiration for the password used for the API I presume …
By the way, if you would like to reuse the same password (by default you can not reuse a password that was already used before) you can issue the following command to clear the  password history before changing the password:
echo “” > /etc/security/opasswd