What would be needed to make gentoo work like Guix/Nix ?

[alexander-n8hgeg5e]

I love Gentoo and I thought about whether it would be possible to
add this "functional package management" feature to Gentoo.

I mean basically if you make some system declaration
(I'd love to have it in python) which defines a diff to "/etc"
and then recreate a "/root" somewhere every time you want to update
or when you want a different system to be "checked out",
then wouldn't it be almost enough?

Probably emerge should run inside the new system tree and not with
the system tree as target because it could change the results,
which should preferably be bit identical.
The ebuilds already have their manifests and are hashed and can be used in the system declaration.

It could work like this:
Everytime you compile a package only the dependencies are checked out and the system
state of all the package versions gets recorded for the next time this package is needed.
The next time if some other package needs this package,
the recorded state is checked out from binpkgs and then emerge is called as usual.

The system declaration could live in /etc
and (if needed) only one single file determines which one is active.
The single file hopfully does not change the compilation results.

Emerge can check out binpkgs.
Only some "meta" program would need to read something like /etc/portage/system-declaration.d/default
and then use emerge to calculate a dependency tree,
then checkout some stage-x archive as base.
After updating the toolchain the whole toolchain can be checked out as binpkg.


Did I miss something ?
Is it possible ?

I dream of defining the system like this:

[pingtoo]

alexander-n8hgeg5e,

it is a little bit hard to follow since I don't have the original idea. But my guess is that you want to use declarative way to describe current system state. It sound that NixOS but I am not sure if that is the right one.

Let me ask, can you use a pseudo logic (but use a close to gentoo way as possible) to do what you want so can help I understand better? I have feeling Gentoo may already do some degree of what you want.

[szatox]

There are automation systems like ansible, salt, puppet and probably many more.
Looks like a decent starting point.

I used to work with ansible, one caveat was that it would not remove anything unless this thing was declared as absent, so adding a thing to a config and then removing it would result in that thing being installed on the target system, but not tracked. This approach worked fine for us; runnning a few thousands of servers we really didn't want to accidentally break with a single command, BUT since the machines had their own memories, builds weren't _really_ fully reproducible like some of those projects advertise.

You'd need an insane amount of patience to fully declare the default configuration though, so we just never did.

[alexander-n8hgeg5e]

[pingtoo]

alexander-n8hgeg5e,

So if you have follow the Configuration Management methodology, you will know some of terminologies. It is like property, state, converge and so on.

I don't think Gentoo have anything ready mode to do what you described. I also think it is not Gentoo's state of direction for making such system. I think Gentoo is doing what it is good at doing on how to custom a system to one's desire. However how to refine the customisation is should left with its user.

I think if you use CM tools like puppet, ansible or cfengine on top of Gentoo it may archive your desire.

I think manually if I want to do what you described, I would place all the configuration file (/etc for example) and /var/lib/portage/world as well add /etc/portage/sets/ into RCS (git for example) and tag/branch each base/stage as some sort of profile (branch) and use RCS check out as you described as way to switch between profile. Once a profile checked out, first emerge depclean than emerge world should be able do closely to your design.

[alexander-n8hgeg5e]

[pingtoo]

[spica]

[alexander-n8hgeg5e]

[sam_]

I don't have the time at the moment to get into a full discussion about the differences, but I'd like to note that declarative configuration doesn't imply isolation per-packages or becoming fully nix-like.

[alexander-n8hgeg5e]

[pingtoo]

In general Portage is a system already did what you described. Except it is implemented in a reversed order of your description.

Imagine, in a declarative Portage design, you would put all the desired program/application into the "world" file and you will run "emerge world" which in tern will examine current state and start finding resolution to bring current state to the desired state. This is how Portage is doing now.

Except its current implementation seems more toward to a Programmer mind where you ran a command (emerge <something>) first and because the <something> was not explained as "state" therefor it is not intuitively think it is asking change "state".

Portage was never "promised" that every invocation will correctly take you to the intended result, In fact as we all know emerge usually will take several round before it will settle down to a execution plan. And what you described now is more or less an optimisation of the execution plan. As we understood "Optimisation" is a trade off, you trade time with space, you can either save time or save space. Using "bin host" and/or COW file system is just trading space with time, It dose not change the design principle of Portage.

If I have a use case where I would like to switch my workstation from state to state I would use Cfengine together with Git. I prefer Cfengine over other like Ansible or Puppet because I like Cfengine 's design idea of targeting single machine as the principle entity as opposite to Ansible/Puppet assume there always a Group of something.

I would utilize Git to store current state (The current state's "Property' will include system/application configuration file and the "world" file) in a branch and the branch name is the named state (or "Profile" as I call it) I will utilize Cfengine's command line argument '-D <define>' as way to indicate state changes. and Cfengine will in tern check out the "<define>"(branch) and compare with current state, use cfengine builtin dependency resolution strategy to come up with a execution place and carry it out.

[alexander-n8hgeg5e]

[pingtoo]