208 lines
4 KiB
Markdown
208 lines
4 KiB
Markdown
---
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marp: true
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title: Declarative Distributions
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description: Declarative Distributions
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theme: uncover
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class:
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- invert
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transition: fade
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paginate: true
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---
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# <!--fit--> Declarative Distros
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---
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# Quick Disclamer
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We are both GNU Guix Users
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While we will try to talk about generalities of declarative operating system paradigms, Guix and Nix specific things, etc, we may get some Nix (and even Guix) things wrong.
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---
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# What is a Declarative Distro?
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### What does it mean?
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---
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- A operating system defined by configuration
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- Without state
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- System is reproducible
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---
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# Declarative v. Imperative
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- Most distros are imperative
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- You give them commands to get a result
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- Nix and Guix are declarative
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- You define a wanted end state and Guix/Nix gets you there its way
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---
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# Reproducible
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- Systems have a given configuration
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- Configuration can duplicate systems
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- If you pin versions, you can make your system completely reproducible
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- Everything is isolated
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---
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# Reproducible
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---
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# Isolation
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- Packages are built in isolated packages
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- No random spare files in file system
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- Anything not being used by a profile is eligible for garbage-collection
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- All state is containted
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- Preserves state-less root
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---
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# Stability
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- Reproducibility and Isolation ensure the ability to rollback
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- Always have some working system state
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- Since any transaction is atomic, it either works or doesn't
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- Your system will never be left in a half updated state that is difficult to recover
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---
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# NixOS
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- Released Jun 2003
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- Eelco Dolstra
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- Nix package manager (nix)
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- Nix language
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- Systemd
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- Wrote like an entire research paper on the theory behind Nix
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---
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# Guix
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- Released 2012
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- Forked from Nix
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- Guix package manager (guix)
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- GNU Guile (scheme/lisp)
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- GNU Shepherd
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- Not GNU/Herd
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---
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# Declarative Package Management
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## `nix` and `guix` commands
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---
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### Declarative Package Management
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- Update system repositories
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- Build and/or install packages
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- Manage `the store`
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---
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### Distro Store
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- Guix `/gnu/store`
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- Nix `/nix/store`
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- Stores all package and system files
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- Partially based off of configuration
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---
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### What is the store like?
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- Lots of files that look like {hash}-package-version
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- Hash is derived from a build dependency graph
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- A program can use any version of a library it needs
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- A program build hash is unique, if any dependency changes the hash will as well.
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### Distro Profile
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- Guix `~/.guix-profile`
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- Nix `~/.nix-profile`
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- Symlink Read only system
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- Links store to current profile
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- Based off configuration
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---
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- Store holds system and package files
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- Profile links to those files
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---
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### Multidirection
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```bash
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$ which gcc
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/home/tylerm/.guix-home/profile/bin/gcc # profile
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$ readlink /home/tylerm/.guix-home/profile/bin/gcc
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/gnu/store/spxcaq8gnmckhzz9a1wm3qc9dmz5bvsd-gcc-toolchain-12.3.0/bin/gcc # store
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```
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---
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## Multiple Profiles
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- System Profile (All users)
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- Good to contain system needed pacakges
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- Graphics drivers
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- Zsh
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- User Profile (Specific user)
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- Good to contain all user data
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- Browser
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- Applications
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- DE/WM
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---
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## To Build The System
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- Package manager takes in user and system configuration
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- Downloads needed data into store
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- Prebuilt, signed binaries are called "substitutes"
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- Build any needed packages
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- Symlinks the user and system profiles
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---
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## Temporary Packages
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- Nix and Guix allow installing packages temporarily
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- Uses contained environment
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- `guix shell <package>`
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- `nix shell -p <package>`
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---
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## What is a package?
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- Since Nix and Scheme are functional, packages are immutable pure functions
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- They define everything from:
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- Inputs
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- Dependencies
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- Expected Outputs
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- Build environment
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- Builds are completely isolated from one another
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- You cannot forget to define a dependency
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- You can guarantee that package will build once you get it working
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