Draft: Mount the nix store from hut in compute nodes #66

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rarias wants to merge 11 commits from shared-nix-store into master
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@ -38,37 +38,27 @@
# Mount an overlay in /nix/store using as lower layer the NFS store and upper
# layer the disk nix store. The destination is still the nix store in
# /nix/store (confusing). We need rw access, as the daemon need to write the
# lock files to build derivations locally.
# HACK: Use /nix//store to prevent the overlay to be mounted on boot, see:
# https://github.com/NixOS/nixpkgs/blob/17a46d09ac123d0da3a26855bf3af7db01f9c751/nixos/lib/utils.nix#L14
fileSystems."/nix//store" = {
device = "overlay";
fsType = "overlay";
options = [
# lock files to build derivations locally. Use a systemd mount unit directly
# so we can specify the LazyUmount option and we avoid having it mounted
# in the stage1 before systemd.
systemd.mounts = [
{
what = "overlay";
type = "overlay";
where = "/nix/store";
# We need the local-fs.target to be ready, so the network interfaces can
# be configured to the network.target is reached. So make this a netdev
# mount.
"_netdev"
"lowerdir=/mnt/hut-nix-store,upperdir=/nix/store,workdir=/mnt/nix-work"
"x-systemd.requires-mounts-for=/nix/store"
# We need to wait for the NFS mount
"x-systemd.requires-mounts-for=/mnt/hut-nix-store"
];
depends = [ "/nix/store" "/mnt/hut-nix-store" "/mnt/nix-work" ];
options = "_netdev,lowerdir=/mnt/hut-nix-store,upperdir=/nix/store,workdir=/mnt/nix-work";
description = "Overlay /nix/store mount";
mountConfig = {
LazyUnmount = true;
};
unitConfig = {
# We need to wait for the NFS mount
RequiresMountsFor = "/nix/store /mnt/hut-nix-store";
Before = "remote-fs.target";
};
# Maybe we should move it to a systemd mount, so we avoid the /nix//store
# hack. Example (not tested):
# systemd.mounts = [
# {
# what = "overlay";
# type = "overlay";
# where = "/nix/store";
# options = "lowerdir=/mnt/hut-nix-store,upperdir=/nix/store,workdir=/mnt/nix-work";
# description = "Overlay nix store mount";
# requires = [ "hut-nix-store.mount" ];
# after = [ "mnt-hut\\x2dnix\\x2dstore.mount" ];
# before = [ "nix-daemon.service" ];
# }
# ];
}
];
}