WARNING:Since the GA of vSphere5 the script below has stopped working. When ever it executes it fails to install to the SQL database, and instead tries to install SQL Express instead. Whilst documentation has been released on how to do an unattend vCenter5 install - no such document appears forthcoming on VMware Update Manager at the moment.
The scripted install of VUM is very much the same as vCenter, except the way you specify the database type you want to use is different - you use parameter VCI_DB_SERVER_TYPE to indicate you want to use an existing external database for the installation, rather than the embedded SQL Express method.
Also it it supports the ability to specify which location you want the patches and updates to be downloaded to with the VMUM_DATA_DIR parameter. I've always installed VUM to the same Windows Instance as vCenter, and given the vCenter a seperate D: drive to hold the downloads.
E:\updateManager\VMware-UpdateManager.exe /L1033 /v" /qr WARNING_LEVEL=0 VMUM_SERVER_SELECT=vcnyc.corp.com VMUM_DATA_DIR=\"D:\" VC_SERVER_IP=vcnyc.corp.com VC_SERVER_ADMIN_USER=\"corp\administrator\" VC_SERVER_ADMIN_PASSWORD=\"Password1\" VCI_DB_SERVER_TYPE=Custom DB_DSN=\"VMware VUM\" DB_USERNAME=\"vumdbuser-nyc\" DB_PASSWORD=\"Password1\"