write etc/nix-store-paths in systemConfiguration

this is step 1 of min-collect-garbage, no point implementing
deletion ourselves when rm -r exists

(arguably no point in implementing any of it, but this is the bit we
can't do efficiently in bourne shell - it means we're reading the
store-paths list once instead of grepping it afresh for every entry in
/nix/store/)

modules/jffs2.nix

@@ -5,7 +5,6 @@
 , ...
 }:
 let
-  inherit (pkgs) closureInfo;
   inherit (lib) mkIf;
 in
 {
@@ -36,11 +35,7 @@ in
           mkdir -p $TMPDIR/empty/nix/store/
           cp ${systemConfiguration}/bin/activate $TMPDIR/empty/activate
           ln -s ${pkgs.s6-init-bin}/bin/init $TMPDIR/empty/init
-          pkgClosure=${closureInfo {
-             rootPaths = [ systemConfiguration ];
-           }}
-          cp $pkgClosure/registration nix-path-registration
-          grafts=$(sed < $pkgClosure/store-paths 's/^\(.*\)$/--graft \1:\1/g')
+          grafts=$(sed < ${systemConfiguration}/etc/nix-store-paths 's/^\(.*\)$/--graft \1:\1/g')
           mkfs.jffs2 --compression-mode=size ${endian} -e ${config.hardware.flash.eraseBlockSize} --enable-compressor=lzo --pad --root $TMPDIR/empty --output $out  $grafts --squash --faketime
         '';
     };

pkgs/min-copy-closure/default.nix

@@ -8,9 +8,13 @@
   buildInputs = [ ];
   propagatedBuildInputs = [ cpio openssh nix ];
   src = ./.;
+  makeFlags = [ "min-list-garbage" ];
   installPhase = ''
     mkdir -p $out/bin
-    cp min-copy-closure.sh $out/bin/min-copy-closure
-    cp liminix-rebuild.sh $out/bin/liminix-rebuild
+    for i in min-copy-closure liminix-rebuild; do
+      echo $i
+      cp ''${i}.sh $out/bin/$i
+    done
+    cp min-list-garbage $out/bin
   '';
 }

pkgs/min-copy-closure/liminix-rebuild.sh

@@ -12,4 +12,4 @@ fi
 toplevel=$(nix-build "$@" -A outputs.systemConfiguration --no-out-link)
 min-copy-closure $target_host $toplevel
 $ssh_command $target_host cp -v -fP $toplevel/bin/* /persist
-$ssh_command $target_host "sync; reboot"
+$ssh_command  $target_host "sync; source /etc/profile; reboot"

pkgs/min-copy-closure/min-list-garbage.c

@@ -0,0 +1,79 @@
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <string.h>
+#include <unistd.h>
+
+typedef char hash_t[32];
+hash_t *hash_list = NULL;
+int hash_list_entries = 0;
+int hash_list_size = 0;
+
+int add_list_entry(char *name)
+{
+    name += strlen("/nix/store/");
+    if(hash_list_entries >= hash_list_size) {
+	if(hash_list_size == 0) hash_list_size =  4;
+	hash_list_size = hash_list_size * 2;
+	hash_list = realloc(hash_list, hash_list_size * sizeof(hash_t));
+    }
+    strncpy(hash_list[hash_list_entries++], name, 32);
+    printf("%d %d\n", hash_list_entries, hash_list_size);
+}
+
+int read_list(char *filename)
+{
+    char s[1024];
+    FILE *fp;
+    if(fp = fopen(filename, "r")) {
+	while(fgets(s, 1024, fp)) {
+	    if(strrchr(s, '\n')) {
+		add_list_entry(s);
+	    } else {
+		puts("hash list entry too long");
+		exit(1);
+	    }
+	}
+    }
+    fclose(fp);
+}
+
+int on_list(char *name)
+{
+    int i;
+    for(i = 0; i < hash_list_entries; i++) {
+	if(!strncmp(hash_list[i], name, 32)) {
+	    return 1;
+	}
+    }
+    return 0;
+}
+
+int main(int argc, char * argv[])
+{
+    struct dirent * de;
+    DIR  * dirp;
+    char hash[32];
+
+    if(argc < 2) {
+	puts("Usage: min-list-garbage store-paths-file\n\nChecks all store paths against the list of expected paths in store-paths-file,\n and prints any which are present unexpectedly");
+	exit(1);
+    }
+
+    read_list(argv[1]);
+    
+    if((dirp = opendir("/nix/store")) == NULL) {
+	puts("can't open /nix/store");
+	exit(1);
+    }
+
+     while(de = readdir(dirp)) {
+	if(strlen(de->d_name) >= 32) {
+	    strncpy(hash, de->d_name, 32);
+	    if(!on_list(hash)) puts(de->d_name);
+	}
+    }
+
+    closedir(dirp);
+}

pkgs/systemconfig/default.nix

@@ -8,6 +8,7 @@
   writeText
 , lib
 , s6-init-bin
+, closureInfo
 , stdenv
 }:
 let
@@ -61,7 +62,8 @@ let
     }
   '';
 in attrset:
-  stdenv.mkDerivation {
+  let makedevs = activateScript attrset;
+  in stdenv.mkDerivation {
     name="make-stuff";
     src = ./.;
 
@@ -69,11 +71,13 @@ in attrset:
     LDFLAGS  = "-static";
 
     postConfigure = ''
-      cp ${activateScript attrset} makedevs.c
+      cp ${makedevs} makedevs.c
     '';
     makeFlags = ["makedevs"];
     installPhase = ''
-      mkdir -p $out/bin
+      closure=${closureInfo { rootPaths = [ makedevs ]; }}
+      mkdir -p $out/bin $out/etc
+      cp $closure/store-paths $out/etc/nix-store-paths
       $STRIP --remove-section=.note  --remove-section=.comment --strip-all makedevs -o $out/bin/activate
       ln -s ${s6-init-bin}/bin/init $out/bin/init
     '';