Pros/cons of fresh install (vs upgrade)

[psycho]

I imagine this has been asked many times, but if so I can't find the threads, and in any case it's the kind of thing that might change over time as the software evolves... so I'm going to ask it (again, probably). Are there any significant advantages to creating a fresh Gentoo system from scratch (via the handbook), over updating an old system?

This one is only four years old, so it looks like I gave in to the temptation to recreate it from scratch in 2021. I'm feeling that temptation again... a vague mistrust of portage, like a belief that major updates (profile changes, major DE version upgrades, etc.) will somehow leave little bits of junk around my system rather than keeping things pristine. Is there any real benefit at all if I give in to this temptation and create a fresh system, or does portage really do such a flawless job of updates that a fresh install will basically be identical to an old-but-updated system, except for the obvious fact that I'll have to sink a lot of time into setup and customisation that's already done if I just keep updating? I'm planning to clone this system onto several other boxes, so I do want it to be as tidy as possible before doing that: my instinct is to build from scratch because this "feels" tidier, but it's always quite a time-consuming job, so I don't want to do it if it's just an obsessive ritual with no real value (because portage is so scrupulous at purging unnecessary files and generally making updated systems just like new ones).

[pingtoo]

I do static gentoo setup (don't mean static /dev etc...) I don't sync /var/db/repos/gentoo, it is kept at the day the entire system built. This is because I want a stale system. I want my computer serve me for what I want to do, not to serving computer on what it tell me need to do.

because my usage is very simple, I just browse internet, use emacs for some automation coding. Use docker for experimental stuff, occupationally use VM for testing boot/kernel. I decide only update once a year and always rebuild from scratch. I maintain a /etc/portage/sets/stage4 for target nodes application installation. user data store on NFS servers.

So I find least concern on Gentoo rolling practice and I do want Gentoo's stability because there are many in community who do all the testing. for that I do grateful for Gentoo community and Gentoo's developer and maintainer.

[pietinger]

psycho,

IF you have on your old system a 17.0 or 17.1 profile THEN I suggest to do a new installation. Why? Because updating to the current 23.0 profile means you must do an "emerge -e" [*] ... you surely know what that does ... ... in my opinion, an update would take longer than a new installation. Just backup your /home and /etc to an external disk ... and copy back some (=not all) of your settings in /etc to the new machine.

*) number 16 of: https://www.gentoo.org/support/news-items/2024-03-22-new-23-profiles.html
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[szatox]

Well, long-overdue updates tend to take quite a bit of time too, and eventually become slower than a reinstall.
You might try to take a shortcut copying /etc and /var/lib/portage over to a new stage3, resetting the profile to a sane value (one matching the stage3) and running emerge @world.
Not sure how well it would actually go in practice, emerge will likely tell you to to flip some use flags or do some other changes via auto-unmask, but it should just be compilation afterwards. Even if emerge complains a bit, it looks much better than either of the "pure" options.*

* Assuming that you already know what you're doing, and that handbook you mentioned only serves you as a checklist. If you're not comfortable setting up a new system blindfolded, taking shortcuts will just confuse you.
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