So this is probably a case where I’m asking the question in the wrong forum, or perhaps I should ask an LLM instead of chatting with humans about this. But, I was curious: I did a sudo apt full-upgrade on one of my PureOS machines recently, and it launched a prompt saying that my sshd_config had diverged from the standard, and that the package maintainer version in PureOS Byzantium had changed.
The prompt was asking me if I wanted to keep my current version, use the new version from package maintainer, view the diff between them and then merge, etc. I was probably going to view the diff, but as I stopped to navigate to the diff viewing function, my finger slipped and I pressed one of the ENTER keys in my keyboard configuration, which ended up exiting the prompt prematurely and going with one of the options.
For PureOS Byzantium, if I wanted to review exactly what changed in the default sshd_config, what’s the best place to see those differences? I might want to do some research and see if I can create a hybrid config between whatever Purism changed, and what I had changed, but I’ll need to be able to identify both sets of changes now after-the-fact.
I don’t know a really easy and good way of doing this, but one alternative to what FranklyFlawless said is that you could try to start a container or a VM or something like that, with a default PureOS installation in it, then you can look there to see the default contents of that config file and you can compare that to your own version of the file.
Another way would be to first backup all your current config files related to the package in question (maybe openssh-server in this case), then remove the package and reinstall it from scratch, so that you get whatever the default config is. Then compare that to your own backed up config, and finally change to the config you want.
It would have been nice if there was a command like “show me the default contents of the config file x from package y” but I’m not sure if there exists any such command.
The default sshd configuration is in /usr/share/openssh/sshd_config
which is supplied by the openssh-server package.
I don’t know whether or not Purism modifies the debian openssh-server source. If so, the Purism git repository for openssh-server can be cloned, then the history of changes to /usr/share/openssh/sshd_config can be easily viewed with gitk or any other git history browser. If not, the debian git repository for openssh-server should be easy to find.
You might have multiple copies of openssh-server_*_arm64.deb in /var/cache/apt/archives/
In that case, you can extract /usr/share/openssh/sshd_config from each of them.