I found that there is an intermittent problem with upgrading Domino 9.0 from Domino 8.5.3 on ZLINUX.  When I upgraded 3 ZLINUX servers from Domino 8.5.3 to Domino 9.0, 2 of the servers did not start after the upgrade, although I had set them to start locally (Local Server Startup) after the upgrade. Instead there was only a cryptic error message 24576 displayed on the console, but there was no other explanation about what the issue was. Upon checking the notes.ini file, I found that this file was set to be "read only", not writeable. Once I changed this property using chmod (chmod 755 notes.ini), the server started properly.  I am attaching a copy of the screenshot below (in this posting)

This is an intermittent problem but which I have also experienced on Domino 8.5.3 running on ZLINUX and which I have talked to IBM support about. That problem was also easily fixed by changing the permissions on the notes.ini using the chmod command once you were aware of this.