* Revert r13150: now that we use private namespaces for the chroot, we

don't have to put the chroot in /nix/var/nix/chroots anymore.
  They're back in /tmp now.

src/libmain/shared.cc

@@ -138,7 +138,6 @@ static void initAndRun(int argc, char * * argv)
     nixConfDir = canonPath(getEnv("NIX_CONF_DIR", NIX_CONF_DIR));
     nixLibexecDir = canonPath(getEnv("NIX_LIBEXEC_DIR", NIX_LIBEXEC_DIR));
     nixBinDir = canonPath(getEnv("NIX_BIN_DIR", NIX_BIN_DIR));
-    nixChrootsDir = canonPath(getEnv("NIX_CHROOTS_DIR", nixStateDir + "/chroots"));
 
     string subs = getEnv("NIX_SUBSTITUTERS", "default");
     if (subs == "default") {

src/libstore/build.cc

@@ -1657,7 +1657,7 @@ void DerivationGoal::startBuilder()
 #if CHROOT_ENABLED
         /* Create a temporary directory in which we set up the chroot
            environment using bind-mounts. */
-        chrootRootDir = createTempDir(nixChrootsDir, "chroot-nix");
+        chrootRootDir = createTempDir("", "nix-chroot");
 
         /* Clean up the chroot directory automatically. */
         autoDelChroot = boost::shared_ptr<AutoDelete>(new AutoDelete(chrootRootDir));

src/libstore/globals.cc

@@ -16,7 +16,6 @@ string nixDBPath = "/UNINIT";
 string nixConfDir = "/UNINIT";
 string nixLibexecDir = "/UNINIT";
 string nixBinDir = "/UNINIT";
-string nixChrootsDir = "/UNINIT";
 
 bool keepFailed = false;
 bool keepGoing = false;

src/libstore/globals.hh

@@ -35,12 +35,6 @@ extern string nixLibexecDir;
 /* nixBinDir is the directory where the main programs are stored. */
 extern string nixBinDir;
 
-/* nixChrootsDir is the directory where we create chroot environments
-   (when chroot builds are enabled).  We don't put these under /tmp to
-   prevent "rm -rf /tmp" from recursing into /nix/store via the bind
-   mounts in the chroots. */
-extern string nixChrootsDir;
-
 
 /* Misc. global flags. */