Unable to log into vCenter Appliance via Web

With everyone scrambling to patch the latest vulnerability to hit the VMware vCenter product, I came across some strange behaviour from our very own vCenter appliance running 6.7. When attempting to log into the web gui of the appliance, I was repeatedly getting a bad credentials error message.

I went round and round in circles trying to confirm I had the correct credentials, testing against vSphere etc… Eventually I started to suspect the issue was with the appliance itself.

Turned out I was on the right track - a service that powers the web gui was disabled on the appliance.

If you suspect something similar from your appliance, do the following to confirm and resolve:

1. Log into your appliances IP address, DNS or FQDN via SSH and login as root
2. Run systemctl status applmgt - This should return a status of DEAD
3. Run systemctl list-unit-files - Look for our applmgt service. It should be set to Masked.

For reasons unknown, the required service’s unit files (the configuration files of the service) have been symlinked to /dev/null. This is otherwise known as Masking. Masking is the Linux equivalent to disabling a service. This is only done if you want a service to not run under any circumstances (including at boot and manually by a user). We need to remove this symlink and restart the service.

1. Run systemctl unmask applmgt
2. Run systemctl list-unit-files - Look for our applmgt service once more. This time, it should be set to Enabled
3. Run systemctl restart applmgt to kick off the service.

Now retry logging into the vCenter appliance’s web gui. With any luck, you should be back to normal.