Use --zstd flag in tar

It is faster then Gzip and available in MEEP FPGA cluster.

.gitlab-ci.yml

@@ -1,6 +1,26 @@
 build:lagarto-ox:
   stage: build
+  when: manual
   tags:
     - nix
   script:
     - nix develop -L .#lagarto-ox --command fpga/run-remotely.sh fpgalogin1:ci
+
+build:lagarto-ox-tarball:
+  stage: build
+  when: manual
+  tags:
+    - nix
+  script:
+    - nix build -L .#nixosConfigurations.lagarto-ox.pkgs.fpga-tarball
+    - cd result
+    - out=/ceph/home/gitlab-runner/public_html/nixos-riscv/
+    - fn=$(ls | head -1)
+    - cp $fn $out/$fn
+    - rm -f $out/latest.tar.zst
+    - ln -s $out/$fn $out/latest.tar.zst
+    - cd ..
+    - rm result
+    - |
+      echo "Pinned: https://jungle.bsc.es/~gitlab-runner/nixos-riscv/$fn"
+      echo "Latest: https://jungle.bsc.es/~gitlab-runner/nixos-riscv/latest.tar.zst"

lagarto-ox.nix

@@ -546,6 +546,91 @@
       EOF
     '';
 
+    # A tarball with all the parts to boot NixOS in a FPGA
+    fpga-tarball = let
+      build = config.system.build;
+    in prev.stdenv.mkDerivation rec {
+      name = "nixos-riscv";
+      src = ./fpga;
+
+      COMMIT    = if self ? rev then self.rev
+        else throw ("Refusing to build tarball from a dirty Git tree!");
+
+      TOPLEVEL  = build.toplevel;
+      OPENSBI   = final.opensbi;
+      KERNEL    = build.kernel;
+      INITRD    = build.initialRamdisk;
+      ROOTFS    = build.sdImage;
+      UBOOT_ENV = final.uboot-env;
+      BITSTREAM = final.bitstream;
+      BOOTROM   = final.bootrom;
+      bitName = builtins.baseNameOf BITSTREAM;
+
+      unpackPhase = ''
+        mkdir -p src/nixos-riscv
+        ln -s $src fpga
+        fpga/upload.sh src/nixos-riscv
+        chmod +w -R src
+        sourceRoot=src
+      '';
+
+      buildPhase = ''
+        cat > nixos-riscv/README.txt <<EOF
+        -----------------------------------------
+        NixOS image for Lagarto Ox in a U55C FPGA
+        -----------------------------------------
+
+        Author: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
+
+        These files allow you to boot NixOS on Lagarto Ox. They correspond to
+        this commit:
+        
+        https://pm.bsc.es/gitlab/rarias/nixos-riscv/-/commit/${COMMIT}
+
+        Here are the pieces used by this system:
+
+          COMMIT    = ${COMMIT}
+          TOPLEVEL  = ${TOPLEVEL}
+          OPENSBI   = ${OPENSBI}
+          KERNEL    = ${KERNEL}
+          INITRD    = ${INITRD}
+          ROOTFS    = ${ROOTFS}
+          UBOOT_ENV = ${UBOOT_ENV}
+          BITSTREAM = ${BITSTREAM}
+          BOOTROM   = ${BOOTROM}
+        
+        Copy these files into a MEEP FPGA node, then allocate a FPGA node and
+        run from this directory (don't forget the dot at the end):
+        
+        $ ./run-node.sh .
+        
+        That would flash the bitstream and NixOS and boot the whole system
+        until the login, and exit after some inactivity period. You should see
+        this message near the end:
+        
+             __________________
+            < Welcome to NixOS >
+             ------------------
+                       ^__^
+                       (oo)_______
+                       (__)       )/
+                           ||----w |
+                           ||     ||
+        
+            If you can read this message then then you have
+            successfully booted NixOS into the login shell.
+
+        EOF
+      '';
+
+      installPhase = ''
+        mkdir -p $out
+        tar --zstd -cvf $out/${COMMIT}.tar.zst nixos-riscv
+      '';
+
+      nativeBuildInputs = with final.buildPackages; [ rsync zstd ];
+    };
+
     opensbi = prev.opensbi.overrideAttrs (old: rec {
       #version = "1.4";
       version = "1.5";