Merge #284: Fix containers

2bfb4efbd8 make-container: fix usage comment (Erik Arvstedt)
3403795c86 tests: add example scripts (Erik Arvstedt)
ff94985b8b tests: add test 'hardened' (Erik Arvstedt)
c8e73c959e fix 'hardened' profile for NixOS 20.09 (Erik Arvstedt)
44b06aea5a extra-container: 0.5-pre -> 0.5 (Erik Arvstedt)
a359cdfb66 generate-secrets: use pwgen (Erik Arvstedt)
a5a2fc7274 make-container: fix renamed variable (Erik Arvstedt)

Pull request description:

ACKs for top commit:
  nixbitcoin:
    ACK 2bfb4efbd8
  jonasnick:
    utACK 2bfb4efbd8

Tree-SHA512: 421b1fc5bf695d6815f060d129855ae0fecc06f7946ed8ac2bfe53895d7dc9529aad40099fc16844547791010232252f74b1ce32cbc9c6458e6d77f327450e94

examples/configuration.nix

@@ -9,8 +9,7 @@
     # FIXME: The hardened kernel profile improves security but
     # decreases performance by ~50%.
     # Turn it off when not needed.
-    # Source: https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/profiles/hardened.nix
-    <nixpkgs/nixos/modules/profiles/hardened.nix>
+    <nix-bitcoin/modules/presets/hardened.nix>
 
     # FIXME: Uncomment next line to import your hardware configuration. If so,
     # add the hardware configuration file to the same directory as this file.
@@ -208,10 +207,6 @@
   # FIXME: Add custom options (like boot options, output of
   # nixos-generate-config, etc.):
 
-  # If the hardened profile is imported above, we need to explicitly allow
-  # user namespaces to enable sanboxed builds and services.
-  security.allowUserNamespaces = true;
-
   # This value determines the NixOS release with which your system is to be
   # compatible, in order to avoid breaking some software such as database
   # servers. You should change this only after NixOS release notes say you

examples/deploy-qemu-vm.sh

@@ -17,6 +17,8 @@ if [[ ! -v IN_NIX_SHELL ]]; then
     exec nix-shell --run "./${BASH_SOURCE[0]##*/} $*"
 fi
 
+cd "${BASH_SOURCE[0]%/*}"
+
 tmpDir=/tmp/nix-bitcoin-qemu-vm
 mkdir -p $tmpDir