Refactor nixos-install to separate out filesystem build logic
The key distinction I'm drawing is that there's a component that deals with the store of the machine being built, and another component for the store building it. The inner part of it assumes nothing from the builder (doesn't need chroot or root powers) so it can run comfortably inside a Nix build, as well as nixos-rebuild. I have some upcoming work that will use that to significantly speed up and streamline image builds for NixOS, especially on virtualized hosts like EC2, but it's also a reasonable speedup on native hosts.
This commit is contained in:
Dan Peebles
@@ -87,38 +87,6 @@ if ! test -e "$mountPoint"; then
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exit 1
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fi
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# Mount some stuff in the target root directory.
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mkdir -m 0755 -p $mountPoint/dev $mountPoint/proc $mountPoint/sys $mountPoint/etc $mountPoint/run $mountPoint/home
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mkdir -m 01777 -p $mountPoint/tmp
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mkdir -m 0755 -p $mountPoint/tmp/root
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mkdir -m 0755 -p $mountPoint/var
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mkdir -m 0700 -p $mountPoint/root
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mount --rbind /dev $mountPoint/dev
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mount --rbind /proc $mountPoint/proc
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mount --rbind /sys $mountPoint/sys
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mount --rbind / $mountPoint/tmp/root
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mount -t tmpfs -o "mode=0755" none $mountPoint/run
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rm -rf $mountPoint/var/run
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ln -s /run $mountPoint/var/run
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for f in /etc/resolv.conf /etc/hosts; do rm -f $mountPoint/$f; [ -f "$f" ] && cp -Lf $f $mountPoint/etc/; done
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for f in /etc/passwd /etc/group; do touch $mountPoint/$f; [ -f "$f" ] && mount --rbind -o ro $f $mountPoint/$f; done
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cp -Lf "@cacert@" "$mountPoint/tmp/ca-cert.crt"
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export SSL_CERT_FILE=/tmp/ca-cert.crt
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# For Nix 1.7
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export CURL_CA_BUNDLE=/tmp/ca-cert.crt
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if [ -n "$runChroot" ]; then
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if ! [ -L $mountPoint/nix/var/nix/profiles/system ]; then
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echo "$0: installation not finished; cannot chroot into installation directory"
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exit 1
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fi
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ln -s /nix/var/nix/profiles/system $mountPoint/run/current-system
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exec chroot $mountPoint "${chrootCommand[@]}"
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fi
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# Get the path of the NixOS configuration file.
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if test -z "$NIXOS_CONFIG"; then
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NIXOS_CONFIG=/etc/nixos/configuration.nix
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@@ -130,121 +98,60 @@ if [ ! -e "$mountPoint/$NIXOS_CONFIG" ] && [ -z "$closure" ]; then
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fi
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# Create the necessary Nix directories on the target device, if they
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# don't already exist.
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mkdir -m 0755 -p \
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$mountPoint/nix/var/nix/gcroots \
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$mountPoint/nix/var/nix/temproots \
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$mountPoint/nix/var/nix/userpool \
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$mountPoint/nix/var/nix/profiles \
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$mountPoint/nix/var/nix/db \
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$mountPoint/nix/var/log/nix/drvs
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mkdir -m 1775 -p $mountPoint/nix/store
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chown @root_uid@:@nixbld_gid@ $mountPoint/nix/store
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# There is no daemon in the chroot.
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unset NIX_REMOTE
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# We don't have locale-archive in the chroot, so clear $LANG.
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export LANG=
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export LC_ALL=
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export LC_TIME=
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# Builds will use users that are members of this group
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extraBuildFlags+=(--option "build-users-group" "$buildUsersGroup")
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# Inherit binary caches from the host
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# TODO: will this still work with Nix 1.12 now that it has no perl? Probably not...
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binary_caches="$(@perl@/bin/perl -I @nix@/lib/perl5/site_perl/*/* -e 'use Nix::Config; Nix::Config::readConfig; print $Nix::Config::config{"binary-caches"};')"
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extraBuildFlags+=(--option "binary-caches" "$binary_caches")
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nixpkgs="$(readlink -f "$(nix-instantiate --find-file nixpkgs)")"
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export NIX_PATH="nixpkgs=$nixpkgs:nixos-config=$mountPoint/$NIXOS_CONFIG"
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unset NIXOS_CONFIG
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# Copy Nix to the Nix store on the target device, unless it's already there.
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if ! NIX_DB_DIR=$mountPoint/nix/var/nix/db nix-store --check-validity @nix@ 2> /dev/null; then
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echo "copying Nix to $mountPoint...."
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for i in $(@perl@/bin/perl @pathsFromGraph@ @nixClosure@); do
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echo " $i"
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chattr -R -i $mountPoint/$i 2> /dev/null || true # clear immutable bit
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@rsync@/bin/rsync -a $i $mountPoint/nix/store/
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done
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# Register the paths in the Nix closure as valid. This is necessary
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# to prevent them from being deleted the first time we install
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# something. (I.e., Nix will see that, e.g., the glibc path is not
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# valid, delete it to get it out of the way, but as a result nothing
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# will work anymore.)
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chroot $mountPoint @nix@/bin/nix-store --register-validity < @nixClosure@
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fi
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# TODO: do I need to set NIX_SUBSTITUTERS here or is the --option binary-caches above enough?
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# Create the required /bin/sh symlink; otherwise lots of things
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# (notably the system() function) won't work.
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mkdir -m 0755 -p $mountPoint/bin
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# !!! assuming that @shell@ is in the closure
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ln -sf @shell@ $mountPoint/bin/sh
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# A place to drop temporary closures
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trap "rm -rf $tmpdir" EXIT
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tmpdir="$(mktemp -d)"
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# Build a closure (on the host; we then copy it into the guest)
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function closure() {
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nix-build "${extraBuildFlags[@]}" --no-out-link -E "with import <nixpkgs> {}; runCommand \"closure\" { exportReferencesGraph = [ \"x\" (buildEnv { name = \"env\"; paths = [ ($1) stdenv ]; }) ]; } \"cp x \$out\""
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}
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# Build hooks likely won't function correctly in the minimal chroot; just disable them.
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unset NIX_BUILD_HOOK
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# Make the build below copy paths from the CD if possible. Note that
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# /tmp/root in the chroot is the root of the CD.
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export NIX_OTHER_STORES=/tmp/root/nix:$NIX_OTHER_STORES
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p=@nix@/libexec/nix/substituters
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export NIX_SUBSTITUTERS=$p/copy-from-other-stores.pl:$p/download-from-binary-cache.pl
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system_closure="$tmpdir/system.closure"
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if [ -z "$closure" ]; then
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# Get the absolute path to the NixOS/Nixpkgs sources.
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nixpkgs="$(readlink -f $(nix-instantiate --find-file nixpkgs))"
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nixEnvAction="-f <nixpkgs/nixos> --set -A system"
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expr="(import <nixpkgs/nixos> {}).system"
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system_root="$(nix-build -E "$expr")"
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system_closure="$(closure "$expr")"
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else
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nixpkgs=""
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nixEnvAction="--set $closure"
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system_root=$closure
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# Create a temporary file ending in .closure (so nixos-prepare-root knows to --import it) to transport the store closure
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# to the filesytem we're preparing. Also delete it on exit!
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nix-store --export $(nix-store -qR $closure) > $system_closure
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fi
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# Build the specified Nix expression in the target store and install
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# it into the system configuration profile.
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echo "building the system configuration..."
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NIX_PATH="nixpkgs=/tmp/root/$nixpkgs:nixos-config=$NIXOS_CONFIG" NIXOS_CONFIG= \
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chroot $mountPoint @nix@/bin/nix-env \
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"${extraBuildFlags[@]}" -p /nix/var/nix/profiles/system $nixEnvAction
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channel_root="$(nix-env -p /nix/var/nix/profiles/per-user/root/channels -q nixos --no-name --out-path 2>/dev/null || echo -n "")"
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channel_closure="$tmpdir/channel.closure"
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nix-store --export $channel_root > $channel_closure
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# Populate the target root directory with the basics
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@prepare_root@/bin/nixos-prepare-root $mountPoint $channel_root $system_root @nixClosure@ $system_closure $channel_closure
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# Copy the NixOS/Nixpkgs sources to the target as the initial contents
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# of the NixOS channel.
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mkdir -m 0755 -p $mountPoint/nix/var/nix/profiles
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mkdir -m 1777 -p $mountPoint/nix/var/nix/profiles/per-user
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mkdir -m 0755 -p $mountPoint/nix/var/nix/profiles/per-user/root
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srcs=$(nix-env "${extraBuildFlags[@]}" -p /nix/var/nix/profiles/per-user/root/channels -q nixos --no-name --out-path 2>/dev/null || echo -n "")
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if [ -z "$noChannelCopy" ] && [ -n "$srcs" ]; then
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echo "copying NixOS/Nixpkgs sources..."
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chroot $mountPoint @nix@/bin/nix-env \
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"${extraBuildFlags[@]}" -p /nix/var/nix/profiles/per-user/root/channels -i "$srcs" --quiet
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fi
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mkdir -m 0700 -p $mountPoint/root/.nix-defexpr
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ln -sfn /nix/var/nix/profiles/per-user/root/channels $mountPoint/root/.nix-defexpr/channels
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# Get rid of the /etc bind mounts.
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for f in /etc/passwd /etc/group; do [ -f "$f" ] && umount $mountPoint/$f; done
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# nixos-prepare-root doesn't currently do anything with file ownership, so we set it up here instead
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chown @root_uid@:@nixbld_gid@ $mountPoint/nix/store
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mount --rbind /dev $mountPoint/dev
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mount --rbind /proc $mountPoint/proc
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mount --rbind /sys $mountPoint/sys
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# Grub needs an mtab.
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ln -sfn /proc/mounts $mountPoint/etc/mtab
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# Mark the target as a NixOS installation, otherwise
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# switch-to-configuration will chicken out.
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touch $mountPoint/etc/NIXOS
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# Switch to the new system configuration. This will install Grub with
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# a menu default pointing at the kernel/initrd/etc of the new
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# configuration.
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