You upgrade seven Domino servers to 9.0.1 and six of them lose their Httpd.cnf file during the upgrade.
As the upgraded servers initialized, the following was recorded in log.nsf: HTTP Server: Using Web Configuration View HTTP Server: Unable to read httpd.cnf HTTP Server: Shutdown
Neither the dominoinstall.log or upgrade.log made any reference to deleting this file.
It was discovered that after the upgrade the \domino\icons folder was missing. The servers that did not lose the httpd.cnf file still had their \domino\icons folder.
The "Web Services Data Files" option was not selected during the install. Deselecting this option will remove the files specific to HTTP from the previous installation, specifically, the httpd.cnf file.
Resolving the problem
As a workaround, copy the httpd.cnf from another server to the other six servers.
Use caution when you uncheck available options during installation. Previously set options will be removed if not selected.
IBM Technical Support recommends making a backup of this file before upgrading, especially if customizations have been made to the file.