jenkins plugin upgrade goes bad, jenkins hangs on startup… how to revert?

you could restore from backup or… just reinstall old plugin version.

these instructions are taken from this article:

but i’ll reproduce it here because i’ve found them to be super useful and i would be sad if i didnt save a backup copy here in case the original site were to go offline.

For eg:

SEVERE: Failed Loading plugin sauce-ondemand Dependency workflow-job (1.15), workflow-cps (1.15), workflow-basic-steps (1.15), workflow-step-api (1.15) doesn’t exist

Full credit to CHUAN CHUAN LAW for making his notes available at his blog: