I recently upgraded a cluster of SRX5400 from 12.3 to 19.2 and I need to revert it back to 12.3. When I try I get the error:
ERROR "/usr/libexec/ui/downgrade" the bootstrap installer is missing...
Is it possible to downgrade this directly from 19.2 to 12.3? Note that access to the cluster is remote so I can't use the USB method.
Better approach would always be to perform USB install, but since that's not an option for you, you can try the following path to downgrade and see if that works.
19.2 -> 18.4 -> 15.1X49-D220.2 -> 12.3
It is not possible to downgrade directly from 19.2 to 12.3 release. You need to downgrade to interim releases first in order to reach 12.3 release.
I think the following downgrade path should work.
19.2 -> 17.3 -> 12.3
Please check the following document for more information - https://www.juniper.net/documentation/en_US/junos/topics/topic-map/upgrading-and-downgrading-to-upgraded-bsd.html#id-downgrading-from-junos-os-with-upgraded-freebsd