1 files changed, 140 insertions, 0 deletions
diff --git a/nixpkgs/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh b/nixpkgs/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh
new file mode 100644
index 00000000000..0092ee92b62
--- /dev/null
+++ b/nixpkgs/nixos/modules/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.sh
@@ -0,0 +1,140 @@
+#! @bash@/bin/sh -e
+
+shopt -s nullglob
+
+export PATH=/empty
+for i in @path@; do PATH=$PATH:$i/bin; done
+
+usage() {
+    echo "usage: $0 -t <timeout> -c <path-to-default-configuration> [-d <boot-dir>] [-g <num-generations>]" >&2
+    exit 1
+}
+
+timeout=                # Timeout in centiseconds
+default=                # Default configuration
+target=/boot            # Target directory
+numGenerations=0        # Number of other generations to include in the menu
+
+while getopts "t:c:d:g:" opt; do
+    case "$opt" in
+        t) # U-Boot interprets '0' as infinite and negative as instant boot
+            if [ "$OPTARG" -lt 0 ]; then
+                timeout=0
+            elif [ "$OPTARG" = 0 ]; then
+                timeout=-10
+            else
+                timeout=$((OPTARG * 10))
+            fi
+            ;;
+        c) default="$OPTARG" ;;
+        d) target="$OPTARG" ;;
+        g) numGenerations="$OPTARG" ;;
+        \?) usage ;;
+    esac
+done
+
+[ "$timeout" = "" -o "$default" = "" ] && usage
+
+mkdir -p $target/nixos
+mkdir -p $target/extlinux
+
+# Convert a path to a file in the Nix store such as
+# /nix/store/<hash>-<name>/file to <hash>-<name>-<file>.
+cleanName() {
+    local path="$1"
+    echo "$path" | sed 's|^/nix/store/||' | sed 's|/|-|g'
+}
+
+# Copy a file from the Nix store to $target/nixos.
+declare -A filesCopied
+
+copyToKernelsDir() {
+    local src=$(readlink -f "$1")
+    local dst="$target/nixos/$(cleanName $src)"
+    # Don't copy the file if $dst already exists.  This means that we
+    # have to create $dst atomically to prevent partially copied
+    # kernels or initrd if this script is ever interrupted.
+    if ! test -e $dst; then
+        local dstTmp=$dst.tmp.$$
+        cp -r $src $dstTmp
+        mv $dstTmp $dst
+    fi
+    filesCopied[$dst]=1
+    result=$dst
+}
+
+# Copy its kernel, initrd and dtbs to $target/nixos, and echo out an
+# extlinux menu entry
+addEntry() {
+    local path=$(readlink -f "$1")
+    local tag="$2" # Generation number or 'default'
+
+    if ! test -e $path/kernel -a -e $path/initrd; then
+        return
+    fi
+
+    copyToKernelsDir "$path/kernel"; kernel=$result
+    copyToKernelsDir "$path/initrd"; initrd=$result
+    dtbDir=$(readlink -m "$path/dtbs")
+    if [ -e "$dtbDir" ]; then
+        copyToKernelsDir "$dtbDir"; dtbs=$result
+    fi
+
+    timestampEpoch=$(stat -L -c '%Z' $path)
+
+    timestamp=$(date "+%Y-%m-%d %H:%M" -d @$timestampEpoch)
+    nixosLabel="$(cat $path/nixos-version)"
+    extraParams="$(cat $path/kernel-params)"
+
+    echo
+    echo "LABEL nixos-$tag"
+    if [ "$tag" = "default" ]; then
+        echo "  MENU LABEL NixOS - Default"
+    else
+        echo "  MENU LABEL NixOS - Configuration $tag ($timestamp - $nixosLabel)"
+    fi
+    echo "  LINUX ../nixos/$(basename $kernel)"
+    echo "  INITRD ../nixos/$(basename $initrd)"
+    if [ -d "$dtbDir" ]; then
+        echo "  FDTDIR ../nixos/$(basename $dtbs)"
+    fi
+    echo "  APPEND systemConfig=$path init=$path/init $extraParams"
+}
+
+tmpFile="$target/extlinux/extlinux.conf.tmp.$$"
+
+cat > $tmpFile <<EOF
+# Generated file, all changes will be lost on nixos-rebuild!
+
+# Change this to e.g. nixos-42 to temporarily boot to an older configuration.
+DEFAULT nixos-default
+
+MENU TITLE ------------------------------------------------------------
+TIMEOUT $timeout
+EOF
+
+addEntry $default default >> $tmpFile
+
+if [ "$numGenerations" -gt 0 ]; then
+    # Add up to $numGenerations generations of the system profile to the menu,
+    # in reverse (most recent to least recent) order.
+    for generation in $(
+            (cd /nix/var/nix/profiles && ls -d system-*-link) \
+            | sed 's/system-\([0-9]\+\)-link/\1/' \
+            | sort -n -r \
+            | head -n $numGenerations); do
+        link=/nix/var/nix/profiles/system-$generation-link
+        addEntry $link $generation
+    done >> $tmpFile
+fi
+
+mv -f $tmpFile $target/extlinux/extlinux.conf
+
+# Remove obsolete files from $target/nixos.
+for fn in $target/nixos/*; do
+    if ! test "${filesCopied[$fn]}" = 1; then
+        echo "Removing no longer needed boot file: $fn"
+        chmod +w -- "$fn"
+        rm -rf -- "$fn"
+    fi
+done