NixOS - the purely functional Linux distribution

Slides for a lightning talk on NixOS:
- reproducible system configurations using digital signatures
- immutable deployments
- how to detect environment changes using digital signatures
- why NixOS will set you free - upgrade, rollback and test changes without fear that something will break

Transcript

1. The purely functional Linux Distribution
   Lenko Donchev
   @lenkodonchev
   

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2. NixOS is a Linux distribution with a
   unique approach to package and
   configuration management. Built on top
   of the Nix package manager, it is
   completely declarative and makes
   upgrading systems reliable.
   

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3. NixOS will set you FREE.
   You will have no fear of upgrading because in
   NixOS an upgrade will not break anything. You
   will not be afraid to upgrade because rollbacks
   are easy. If something doesn’t work you can
   always go back safely and reliably. Reliability is
   the key.
   

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4. How does it work?
   configuration.nix
   Crypto hash
   0cg52ncqn9lajgdy4njma3wk7lf3591d
   /nix/store/0cg52ncqn9lajgdy4njma3wk7lf3591d
   -systemd-212.tar
   

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5. The basic idea
   /usr/bin/firefox
   Symbolic link
   /nix/store/0cg52ncqn9lajg………../bin/firefox
   

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6. NixOS is similar to GIT
   

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7. Benefits
   

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8. Install multiple versions of applications
   You can have multiple versions of the
   same application installed without any
   side effects.
   

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9. No more Dependency HELL
   Thanks to the crypto hash being part of
   the path to libraries and configuration
   files there is complete isolation between
   different application versions.
   

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10. Reliable upgrades
    While the configuration remains the same, you
    can upgrade your system safely to always obtain
    the same result, as if it were a new, fresh
    installation.
    

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11. Atomic upgrades
    Changes in a configuration are made in a
    transactional way, thus they are atomic,
    and changes are only applied when the
    transaction is finished. For instance, if an
    upgrade is interrupted or fails, the
    previous state continues to work.
    

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12. Rollbacks
    You can always rollback to a previous state. This
    is possible because a new configuration never
    overwrites a previous one. Old installations and
    configurations are kept simultaneously on the
    disk. Rolling back to an old configuration is just
    updating of symbolic links.
    

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13. Test changes safely
    Thanks to the rollback capabilities and
    simultaneous configurations, NixOS
    allows you to test a configuration, and if
    doesn't work just roll it back without fear
    that it will break anything.
    

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14. Reproducible system configurations
    You can copy a configuration from a machine to a
    similar machine and get the same system. This is ideal
    for making changes on test machines before applying
    changes on production machines or for deployments.
    There is a dedicated tool for reproducible deployments
    called NixOps.
    

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15. Mixed model with source and binaries
    Nix builds packages from source or from
    prebuilt binaries available for download
    from a cache server.
    

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16. Consistency
    When a package or configuration changes, all
    the necessary packages or dependencies are
    rebuilt too. The same happens with the kernel
    and the modules . When a library is updated,
    all the packages that use it are linked to the
    new version.
    

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17. Multi-user package management
    In NixOS, the packages installed with the root user are
    available for all the users, but each user can also install
    their own packages in their profile. The packages are
    still stored and managed in the Nix store, and different
    users can have different versions of the same package.
    If two users install the same version of the same
    package, only one copy is stored and shared among
    them.
    

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18. Give it a try!
    

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