matthewpi/README.md

## README.md

      
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    NixOS on Fedora

Please note that these instructions are not offically supported or condoned by Nix and are not guaranteed to always work, but from my testing everything seems to work perfectly fine.
These steps may not be required if NixOS/nix#2374 is resolved.
SELinux

These commands are required for both Fedora Workstation and Fedora Silverblue
sudo semanage fcontext -a -t etc_t '/nix/store/[^/]+/etc(/.*)?'
sudo semanage fcontext -a -t lib_t '/nix/store/[^/]+/lib(/.*)?'
sudo semanage fcontext -a -t systemd_unit_file_t '/nix/store/[^/]+/lib/systemd/system(/.*)?'
sudo semanage fcontext -a -t man_t '/nix/store/[^/]+/man(/.*)?'
sudo semanage fcontext -a -t bin_t '/nix/store/[^/]+/s?bin(/.*)?'
sudo semanage fcontext -a -t usr_t '/nix/store/[^/]+/share(/.*)?'
sudo semanage fcontext -a -t var_run_t '/nix/var/nix/daemon-socket(/.*)?'
sudo semanage fcontext -a -t usr_t '/nix/var/nix/profiles(/per-user/[^/]+)?/[^/]+'
If you are on Fedora Workstation, skip past the Fedora Silverblue section down to Install Nix
Fedora Silverblue

If you are running Fedora Silverblue, you will need to follow these extra steps.
Create the nix directory in a persistent location

sudo mkdir /var/nix
SELinux

You will want to the SELinux contexts for the mounted directory paths as well, it seems to help avoid some weird issues periodically.
sudo semanage fcontext -a -t etc_t '/var/nix/store/[^/]+/etc(/.*)?'
sudo semanage fcontext -a -t lib_t '/var/nix/store/[^/]+/lib(/.*)?'
sudo semanage fcontext -a -t systemd_unit_file_t '/var/nix/store/[^/]+/lib/systemd/system(/.*)?'
sudo semanage fcontext -a -t man_t '/var/nix/store/[^/]+/man(/.*)?'
sudo semanage fcontext -a -t bin_t '/var/nix/store/[^/]+/s?bin(/.*)?'
sudo semanage fcontext -a -t usr_t '/var/nix/store/[^/]+/share(/.*)?'
sudo semanage fcontext -a -t var_run_t '/var/nix/var/nix/daemon-socket(/.*)?'
sudo semanage fcontext -a -t usr_t '/var/nix/var/nix/profiles(/per-user/[^/]+)?/[^/]+'
/etc/systemd/system/mkdir-rootfs@.service

[Unit]
Description=Enable mount points in / for ostree
ConditionPathExists=!%f
DefaultDependencies=no
Requires=local-fs-pre.target
After=local-fs-pre.target

[Service]
Type=oneshot
ExecStartPre=chattr -i /
ExecStart=mkdir -p '%f'
ExecStopPost=chattr +i /

/etc/systemd/system/nix.mount

[Unit]
Description=Nix Package Manager
DefaultDependencies=no
After=mkdir-rootfs@nix.service
Wants=mkdir-rootfs@nix.service
Before=sockets.target
After=ostree-remount.service
BindsTo=var.mount

[Mount]
What=/var/nix
Where=/nix
Options=bind
Type=none

Enable and mount the nix mount and reset the SELinux context.
# Ensure systemd picks up the newly created units
sudo systemctl daemon-reload
# Enable the nix mount on boot.
sudo systemctl enable nix.mount
# Mount the nix mount now.
sudo systemctl start nix.mount
# R = recurse, F = full context (not just target)
sudo restorecon -RF /nix
Install Nix

After you have configured SELinux (and if you are on Silverblue, configured a /nix mount), it's time to install Nix.
sh <(curl -L https://nixos.org/nix/install) --daemon
If you are running Fedora Workstation, you are now ready to rock!  If you are running Fedora Silverblue, you will need to do some additional configuration.
Fedora Silverblue

If you are running Fedora Silverblue, you will need to run these additional steps.  Most likely the installation errored out while setting up systemd.  SELinux on Silverblue prevents systemd from loading the units linked by Nix, while the best solution would be to add a policy or package Nix as an RPM, we will just manually copy the units ourselves.
TODO: Find a way to link the units, that way whenever Nix is updated you don't need to manually edit or copy the units.
# Remove the linked services
sudo rm -f /etc/systemd/system/nix-daemon.{service,socket}
# Manually copy the services
sudo cp /var/nix/var/nix/profiles/default/lib/systemd/system/nix-daemon.{service,socket} /etc/systemd/system/
# Ensure systemd picks up the newly created units
sudo systemctl daemon-reload
# Start (and enable) the nix-daemon socket
sudo systemctl enable --now nix-daemon.socket
Optionally, you may manually modify the nix-daemon units to add a bind to nix.mount to ensure the units activate and deactivate properly if the mount fails or if the mount is unmounted while the daemon is running.  Place the following at the bottom of the [Unit] section in both the nix-daemon.socket and nix-daemon.service units.
After=nix.mount
BindsTo=nix.mount

You have just installed Nix and should be ready to rock!
NOTE: the nix-daemon.socket unit will automatically start nix-daemon.service whenever it is needed, there is no need to enable or manually start the service.