Hello,
If there are Disk Uploads that have not completed (i.e: currently Paused or with Error) and were not canceled the upgrade will fail.This is due to a foreign key being added on 4.2.5, relating image_transfers table to command_entities table.
When the roll-back to the previous RHV-M version finishes, open the Administration Portal and navigate to Storage -> Disks.
there was indeed one disk upload which wasn't finshed. I have canceled it and removed the disk.
If it fails then share your observations with us, so we need to do some manual changes in database. The seconds attempt to update failed to:
Running upgrade sql script '/usr/share/ovirt-engine/dbscripts/upgrade/04_02_1210_add_foreign_key_to_image_transfers.sql'... 2018-08-03 12:45:05,808+0200 DEBUG otopi.plugins.ovirt_engine_setup.ovirt_engine.db.schema plugin.execute:926 execute-output: ['/usr/share/ovirt-engine/dbscripts/schema.sh', '-s', 'localhost', '-p', '5432', '-u', 'engine', '-d', 'engine', '-l', '/var/log/ovirt-engine/setup/ovirt-engine-setup-20180803124017-k94hg1.log', '-c', 'apply'] stderr: psql:/usr/share/ovirt-engine/dbscripts/upgrade/04_02_1210_add_foreign_key_to_image_transfers.sql:1: ERROR: insert or update on table "image_transfers" violates foreign key constraint "fk_image_tran sfers_command_enitites" DETAIL: Key (command_id)=(312f711f-a5c3-477d-8533-82ef88a54b77) is not present in table "command_entities". FATAL: Cannot execute sql command: --file=/usr/share/ovirt-engine/dbscripts/upgrade/04_02_1210_add_foreign_key_to_image_transfers.sql 2018-08-03 12:45:05,809+0200 ERROR otopi.plugins.ovirt_engine_setup.ovirt_engine.db.schema schema._misc:434 schema.sh: FATAL: Cannot execute sql command: --file=/usr/share/ovirt-engine/dbscripts/upg rade/04_02_1210_add_foreign_key_to_image_transfers.sql 2018-08-03 12:45:05,812+0200 DEBUG otopi.context context._executeMethod:143 method exception Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/otopi/context.py", line 133, in _executeMethod method['method']() File "/usr/share/ovirt-engine/setup/bin/../plugins/ovirt-engine-setup/ovirt-engine/db/schema.py", line 436, in _misc raise RuntimeError(_('Engine schema refresh failed')) RuntimeError: Engine schema refresh failed 2018-08-03 12:45:05,815+0200 ERROR otopi.context context._executeMethod:152 Failed to execute stage 'Misc configuration': Engine schema refresh failed The restore for both databases (engine and engine_hirory) fails too: pg_restore: [archiver (db)] Error from TOC entry 7339; 0 0 COMMENT EXTENSION "uuid-ossp" pg_restore: [archiver (db)] could not execute query: ERROR: must be owner of extension uuid-ossp Regards Jan