How find previous Jenkins version after unintentional upgrade?

Our jenkins instance got upgraded somehow overnight! (Yeah I know, sounds stupid.)
We want to roll back to previous version - but not sure what it was.
Will it be in some logs somewhere?

Also we can’t currently log in - although not sure whether we need to at this stage - due to something like:


We just rolled back to a guessed earlier version. When we did the login difficulty was resolved. In fact Jenkins still considered me to be logged in.

A reasonable “fallback” mechanism to find the prior version, if done via “Upgrade Automatically” ( the classic “oops”), is to examine the war file location. The prior jenkins.war file should have been renamed to jenkins.war.bak.

You can either find the SHA:
sha256sum jenkins.war.bak
and look that up in the Past Releases, or you can run this:
jar -tf jenkins.war.bak | grep jenkins-core
and the resulting number will be the release.

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Thanks! Sounds good. I think the guy handling the problem reinstated the old jenkins from the .bak
So I guess in the end we didn’t actually need to know the version upfront.