question about /etc and /var when switching between deployments in a given stateroot

[Davis Roman <davis roman84 gmail com>]

Hello,

I was reading through the ostree documentation specifically the
section on "Assembling a new deployment directory"
(https://ostree.readthedocs.io/en/latest/manual/atomic-upgrades/)

The paragraph states: "
Given a commit to deploy, OSTree first allocates a directory for it.
This is of the form
/boot/loader/entries/ostree-$stateroot-$checksum.$serial.conf.
The $serial is normally 0, but if a given commit is deployed more than
once, it will be incremented. This is supported because
the previous deployment may have configuration in /etc that we do not
want to use or overwrite."

So my question is in regards to how /var and /etc/ are treated when
switching between deployments in a given stateroot.
Initially I was thinking that /etc/ and /var/ are persistent and don't
change. My understanding appears to conflict with the documentation. (
I'm referring to the last line of the above paragraph)

Any clarification would be very helpful,

Thank you,

Davis