Support self-hosted runners and always skip adding a channel

.github/workflows/test.yml

@@ -15,28 +15,14 @@ jobs:
     - run: yarn build
     - name: Install Nix
       uses: ./
+      with:
+        nix_path: nixpkgs=channel:nixos-20.03
     - run: nix-env -iA cachix -f https://cachix.org/api/v1/install
     - run: cat /etc/nix/nix.conf
     # cachix should be available and be able to configure a cache
     - run: cachix use cachix
     - run: nix-build test.nix
 
-  no-channel:
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macos-latest]
-    runs-on: ${{ matrix.os }}
-    steps:
-    - uses: actions/checkout@v2
-    - run: yarn install --frozen-lockfile
-    - run: yarn build
-    - name: Install Nix
-      uses: ./
-      with:
-        skip_adding_nixpkgs_channel: true
-    - run: nix-build test.nix && exit 1 || echo "OK"
-    - run: NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs/tarball/ab5863afada3c1b50fc43bf774b75ea71b287cde nix-build test.nix
-
   custom-nix-path:
     strategy:
       matrix:
@@ -64,7 +50,8 @@ jobs:
     - run: yarn build
     - name: Install Nix
       uses: ./
-      with:
+      with: 
+        nix_path: nixpkgs=channel:nixos-20.03
         extra_nix_config: |
           sandbox = relaxed
     - run: cat /etc/nix/nix.conf

README.md

@@ -4,6 +4,15 @@
 
 Installs [Nix](https://nixos.org/nix/) on GitHub Actions for the supported platforms: Linux and macOS.
 
+# Features
+
+- Quick installation (~4s on Linux, ~20s on macOS)
+- Multi-User mode with sandboxing enabled on Linux
+- [Self-hosted github runner](https://docs.github.com/en/actions/hosting-your-own-runners/about-self-hosted-runners) support
+- Allows specifying Nix installation URL
+- Allows specifying extra Nix configration options
+- Allows specifying `$NIX_PATH` and channels
+
 ## Usage
 
 Create `.github/workflows/test.yml` in your repo with the following contents:
@@ -28,14 +37,36 @@ See also [cachix-action](https://github.com/cachix/cachix-action) for
 simple binary cache setup to speed up your builds and share binaries
 with developers.
 
-## Options `with: ...`
+# Usage with Flakes
+
+```
+name: "Test"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+          # Nix Flakes doesn't work on shallow clones
+          fetch-depth: 0
+    - uses: cachix/install-nix-action@v11
+      with:
+        install_url: https://github.com/numtide/nix-flakes-installer/releases/download/nix-3.0pre20200820_4d77513/install
+        extra_nix_config: |
+          experimental-features = nix-command flakes
+    - run: nix-build
+```
+
+## Inputs (specify using `with:`)
 
-- `install_url`: specify URL to install Nix from (mostly useful for testing non-stable releases)
+- `install_url`: specify URL to install Nix from (useful for testing non-stable releases)
 
-- `nix_path`: set `NIX_PATH` environment variable (if set `skip_adding_nixpkgs_channel` will be implicitly enabled)
+- `nix_path`: set `NIX_PATH` environment variable, for example `nixpkgs=channel:nixos-unstable`
 
-- `skip_adding_nixpkgs_channel`: set to `true` to skip adding nixpkgs-unstable channel (and save ~5s for each job build)
-- `extra_nix_config`: gets appended to `/etc/nix/nix.conf` if passed.
+- `extra_nix_config`: append to `/etc/nix/nix.conf`
 
 ---
 

action.yml

@@ -5,9 +5,7 @@ inputs:
   install_url:
     description: 'Installation URL that will contain a script to install Nix'
   nix_path:
-    description: 'Set NIX_PATH environment variable. If set "skip_adding_nixpkgs_channel" will be implicitly enabled'
-  skip_adding_nixpkgs_channel:
-    description: 'Skip adding nixpkgs-unstable channel'
+    description: 'Set NIX_PATH environment variable.'
   extra_nix_config:
     description: 'gets appended to `/etc/nix/nix.conf` if passed.'
 branding:

lib/install-nix.sh

@@ -7,8 +7,8 @@ add_config() {
 }
 # Set jobs to number of cores
 add_config "max-jobs = auto"
-# Allow binary caches for runner user
-add_config "trusted-users = root runner"
+# Allow binary caches for user
+add_config "trusted-users = root $USER"
 # Append extra nix configuration if provided
 if [[ $INPUT_EXTRA_NIX_CONFIG != "" ]]; then
   add_config "$INPUT_EXTRA_NIX_CONFIG"
@@ -18,19 +18,17 @@ fi
 installer_options=(
   --daemon
   --daemon-user-count 4
+  --no-channel-add
   --darwin-use-unencrypted-nix-store-volume
   --nix-extra-conf-file /tmp/nix.conf
 )
 
-if [[ $INPUT_SKIP_ADDING_NIXPKGS_CHANNEL = "true" || $INPUT_NIX_PATH != "" ]]; then
-  installer_options+=(--no-channel-add)
-else
-  INPUT_NIX_PATH="/nix/var/nix/profiles/per-user/root/channels"
+# On self-hosted runners we don't need to install more than once
+if [ ! -d "/nix/store" ] 
+then 
+  sh <(curl --retry 5 --retry-connrefused -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}") "${installer_options[@]}"
 fi
 
-sh <(curl --retry 5 --retry-connrefused -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}") \
-  "${installer_options[@]}"
-
 if [[ $OSTYPE =~ darwin ]]; then
   # Disable spotlight indexing of /nix to speed up performance
   sudo mdutil -i off /nix
@@ -43,7 +41,7 @@ if [[ $OSTYPE =~ darwin ]]; then
 fi
 
 # Set paths
-echo "::add-path::/nix/var/nix/profiles/per-user/runner/profile/bin"
+echo "::add-path::/nix/var/nix/profiles/per-user/$USER/profile/bin"
 echo "::add-path::/nix/var/nix/profiles/default/bin"
 
 if [[ $INPUT_NIX_PATH != "" ]]; then