Thunderbird and Fedora: what should a package update change?
Posted Oct 22, 2009 1:40 UTC (Thu) by davecb
Parent article: Thunderbird and Fedora: what should a package update change?
Mr Wills notes that if an application changes its data storage format in an upgrade, downgrading could cause data loss or unpredictable behavior.
This is indeed hard, but it's been doable since before Unix v6. I was on HI_Multics.ARPA when they were doing a filesystem layout change, and wondered why things were slow (;-))
To brutally oversimplify, you need to implement a version tracker, an updater and a downdater before rolling out a change. The original work was done at MIT and on the ARPAnet, where repeated remote updates and rollbacks were necessary to keep a prototype network alive.
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