Juju and apt-cacher

I’ve been playing quite a lot lately with Juju and other related software projects, like conjure-up and LXD. They make so easy to spin up and down complex software stacks like OpenStack that you don’t even realize until your hosting provider start alerting you of high traffic consumption. And guess where most of this traffic usage comes from? From installing packages.

So I decided to save on bandwidth by using apt-cacher. It is straightforward and easy to set up and getting it running. In the end, if you follow the steps described in the previous link or this, you will end up with a Perl program listening on your machine in port 3142 that you can use as an Apt cache.

For Juju, one can use a YAML configuration file like this:

apt-http-proxy: http://localhost:3142
apt-https-proxy: http://localhost:3142

Then bootstrap Juju using the following command:

$ juju bootstrap --config config.yaml localhost lxd

For conjure-up is also very easy:

$ conjure-up \
    --apt-proxy http://localhost:3142 \
    --apt-https-proxy http://localhost:3142 \

OpenStack Newton and LXD


This post is about deploying a minimal OpenStack newton cluster atop LXD on a single machine. Most of what is mentioned here is based on OpenStack on LXD.


The rationale behind using LXD is simplicity and feasibility: it doesn’t require more than one x86_64 server with 8 CPU cores, 64GB of RAM and a SSD drive large enough to perform an all-in-one deployment of OpenStack Newton.

According to Canonical, “LXD is a pure-container hypervisor that runs unmodified Linux guest operating systems with VM-style operations at incredible speed and density.”. Instead of using pure virtual machines to run the different OpenStack components, LXD is used which allows for higher “machine” (container) density. In practice, an LXD container behaves pretty much like a virtual or baremetal machine.

For all purposes, I will be using Ubuntu 16.04.02 for this experiment on a 128GB machine with 12 CPU cores and 4x240GB SSD drives configured using software RAID0. For increased performance and efficiency ZFS is also used (dedicated partition separate from the base OS) as a backing store for LXD.


$ sudo add-apt-repository ppa:juju/devel
$ sudo add-apt-repository ppa:ubuntu-lxc/lxd-stable
$ sudo apt update
$ sudo apt install \
    juju lxd zfsutils-linux squid-deb-proxy \
    python-novaclient python-keystoneclient \
    python-glanceclient python-neutronclient \
    python-openstackclient curl
$ git clone https://github.com/falfaro/openstack-on-lxd.git

It is important to run all the following commands inside the openstack-on-lxd directory where the Git repository has been cloned locally.

LXD set up
$ sudo lxd init

The relevant part here is the network configuration. IPv6 is not properly supported by Juju so make sure to not enable. For IPv4 use the subnet and assign the IPv4 address for LXD itself. The DHCP range could be something like to

NOTE: Having LXD listen on the network is also an option for remotely managing LXD, but beware of security issues when exposing it over a public network. Using ZFS (or btrfs) should also increase performance and efficiency (e.g. copy-on-write shall save disk space by prevent duplicate bits from all the containers running the same base image).

Using an MTU of 9000 for container interfaces will likely increase performance:

$ lxc profile device set default eth0 mtu 9000

Next step is to spawn an LXC container for testing purposes:

$ lxc launch ubuntu-daily:xenial openstack
$ lxc exec openstack bash
# exit

An specific LXC profile named juju-default will be used when deploying OpenStack. In particular this profile allows for nesting LXD (required by nova-compute), allows running privileged containers, and preloads certain kernel modules required inside OpenStack containers.

$ lxc profile create juju-default 2>/dev/null || \
  echo "juju-default profile already exists"
$ cat lxd-profile.yaml | lxc profile edit juju-default
Bootstrap Juju controller
$ juju bootstrap --config config.yaml localhost lxd
Deploy OpenStack
$ juju deploy bundle-newton-novalxd.yaml
$ watch juju status

After Juju has finished deploying OpenStack, make sure there is a file named novarc in the current directory. This file is required to be sourced in order to use the OpenStack CLI:

$ source novarc
$ openstack catalog list
$ nova service-list
$ neutron agent-list
$ cinder service-list

Create Nova flavors:

$ openstack flavor create --public \
    --ram   512 --disk  1 --ephemeral  0 --vcpus 1 m1.tiny
$ openstack flavor create --public \
    --ram  1024 --disk 20 --ephemeral 40 --vcpus 1 m1.small
$ openstack flavor create --public \
    --ram  2048 --disk 40 --ephemeral 40 --vcpus 2 m1.medium
$ openstack flavor create --public \
    --ram  8192 --disk 40 --ephemeral 40 --vcpus 4 m1.large
$ openstack flavor create --public \
    --ram 16384 --disk 80 --ephemeral 40 --vcpus 8 m1.xlarge

Add the typical SSH key:

$ openstack keypair create --public-key ~/.ssh/id_rsa.pub mykey

Create a Neutron external network and a virtual network for testing:

$ ./neutron-ext-net \
    -g -c \
    -f ext_net
$ ./neutron-tenant-net \
    -t admin -r provider-router \
    -N internal

CAVEAT: Nova/LXD does not support use of QCOW2 images in Glance. Instead one has to use RAW images. For example:

$ curl http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-root.tar.gz | \
  glance image-create --name xenial --disk-format raw --container-format bare


$ openstack server create \
    --image xenial --flavor m1.tiny --key-name mykey --wait \
    --nic net-id=$(neutron net-list | grep internal | awk '{ print $2 }') \

NOTE: For reasons I yet do not understand, one can’t use a flavor other than m1.tiny. Reason is that this flavor is the only one that does not request any ephemeral disk. As soon as ephemeral disk is requested, the LXD subsystem inside the nova-compute container will complain with the following error:

$ juju ssh nova-compute/0
$ sudo tail -f /var/log/nova/nova-compute.log
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 2078, in _build_resources
    yield resources
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1920, in _build_and_run_instance
  File "/usr/lib/python2.7/dist-packages/nova/virt/lxd/driver.py", line 317, in spawn
    self._add_ephemeral(block_device_info, lxd_config, instance)
  File "/usr/lib/python2.7/dist-packages/nova/virt/lxd/driver.py", line 1069, in _add_ephemeral
    raise exception.NovaException(reason)
NovaException: Unsupport LXD storage detected. Supported storage drivers are zfs and btrfs.

If Cinder is available, create a test Cinder volume:

$ cinder create --name testvolume 10

Persistent loopback interfaces in Mac OS X

One of the things that I miss in Mac OS X is support for multiple loopback addresses. Not just, but anything in the form 127.* (e.g. or

To add an additional IPv4 address to the loopback interface, one can use the following command in a Mac OS X terminal:

$ sudo ifconfig lo0 alias

Problems is that this doesn’t persist across reboots. To make it persist across reboots, one can create a “launchd” daemon that configures this additional IPv4 address. Something like this:

$ cat << EOF | sudo tee -a /Library/LaunchDaemons/com.felipe-alfaro.loopback1.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">

Then, start the service up:

$ sudo launchctl load /Library/LaunchDaemons/com.felipe-alfaro.loopback1.plist

And make sure it did work:

$ sudo launchctl list | grep com.felipe-alfaro
-   0   com.felipe-alfaro.loopback1
$ ifconfig lo0
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
    inet netmask 0xff000000 
    inet6 ::1 prefixlen 128 
    inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 
    inet netmask 0xff000000 
    nd6 options=201<PERFORMNUD,DAD>

And, for the record, it is totally possible to have multiple services like the one before, each one for every additional IPv4 address. Just make sure to name the .plist files differently as well as the services name in the Label tag.

Default user in WSL

The Windows Subsystem for Linux (WSL) defaults to running as the “root” user. In order to change that behavior, just create a Linux user.Let’s imagine this user is named “jdoe”. To have WSL start the session as “jdoe” instead of “root”, just run the following command from a “cmd.exe” window:

C:\Users\JohnDoe> lxrun /setdefaultuser jdoe

Take into account that running any running WSL will be killed inmmediately.

QPID and OpenStack

If you are still using QPID in your OpenStack deployment, be careful with the QPID topology version used. It seems some components in Havana default to version 2 while others in Icehouse default to 1.

To avoid problems, perhaps you want to explicitly set the following configuration option in files like /etc/nova/nova.conf:


How PKI-based tokens from Keystone are authenticated

This article tries to explain how tokens generated by Keystone (using the PKI token format, not UUID) can be authenticated by clients (e.g. cinder, neutron, nova, etc.)

The relevant fragment from /etc/keystone/keystone.conf that specifies the PKI material used to sign Keystone tokens (the signing key, the signing certificate and its corresponding CA certificate, together with key size and key expiration period) usually looks like this (default values are used next):

token_format = PKI
certfile = /etc/keystone/ssl/certs/signing_cert.pem
keyfile = /etc/keystone/ssl/private/signing_key.pem
ca_certs = /etc/keystone/ssl/certs/ca.pem
cert_subject = /C=US/ST=Unset/L=Unset/O=Unset/CN=www.example.com
key_size = 2048
valid_days = 3650

The Keystone client middleware — implemented in the keystone client.middleware.auth_token Python module — verifies the signature of a given Keystone token (data is in IAW CMS syntax). The actual method from this module is cms_verify. This method relies on its counterpart cms_verify defined in keystoneclient.common.cms and requires the actual data, the signing certificate and corresponding CA certificate.

The token’s data, signing certificate and its corresponding CA certificate are stored on local disk, inside a directory specified by the signing_dir option in the keystone_authtoken section. By default, this option is set to None. When None or absent, a temporary directory is created, as one can see in the verify_signing_dir method:

def verify_signing_dir(self):
    if os.path.exists(self.signing_dirname):
        if not os.access(self.signing_dirname, os.W_OK):
            raise ConfigurationError(
                'unable to access signing_dir %s' % self.signing_dirname)
        uid = os.getuid()
        if os.stat(self.signing_dirname).st_uid != uid:
                'signing_dir is not owned by %s', uid)
        current_mode = stat.S_IMODE(os.stat(self.signing_dirname).st_mode)
        if current_mode != stat.S_IRWXU:
                'signing_dir mode is %s instead of %s',
                oct(current_mode), oct(stat.S_IRWXU))
        os.makedirs(self.signing_dirname, stat.S_IRWXU)

When debug is True for any particular OpenStack service, one can see the value of the signing_dir option during startup in the logs:

2015-04-15 19:03:25.069 9449 DEBUG glance.common.config [-] keystone_authtoken.signing_dir = None log_opt_values /usr/lib/python2.6/site-packages/oslo/config/cfg.py:1953

The signing certificate and its corresponding CA certificate are retrieved from Keystone via an HTTP request, and stored on local disk. The methods that implement this in keystone client.middleware.auth_token look like this:

def _fetch_cert_file(self, cert_file_name, cert_type):
    path = '/v2.0/certificates/' + cert_type
    response = self._http_request('GET', path)
    if response.status_code != 200:
        raise exceptions.CertificateConfigError(response.text)
    self._atomic_write_to_signing_dir(cert_file_name, response.text)

def fetch_signing_cert(self):
    self._fetch_cert_file(self.signing_cert_file_name, 'signing')

def fetch_ca_cert(self):
    self._fetch_cert_file(self.signing_ca_file_name, 'ca')

Which translates to HTTP requests to Keystone like this:

2015-04-15 19:03:34.704 9462 DEBUG urllib3.connectionpool [-] "GET /v2.0/certificates/signing HTTP/1.1" 200 4251 _make_request /usr/lib/python2.6/site-packages/urllib3/connectionpool.py:295
2015-04-15 19:03:34.727 9462 DEBUG urllib3.connectionpool [-] "GET /v2.0/certificates/ca HTTP/1.1" 200 1277 _make_request /usr/lib/python2.6/site-packages/urllib3/connectionpool.py:295

As said before, in order to verify the Keystone token, the cms_verify method uses the signing certificate and corresponding CA certificates (as stored on local disk) plus the token data, and passes them to an external openssl process for verification:

def cms_verify(self, data):
    """Verifies the signature of the provided data's IAW CMS syntax.

    If either of the certificate files are missing, fetch them and
    while True:
            output = cms.cms_verify(data, self.signing_cert_file_name,
        except exceptions.CertificateConfigError as err:
            if self.cert_file_missing(err.output,
            if self.cert_file_missing(err.output,
            self.LOG.error('CMS Verify output: %s', err.output)

This translates to having the Keystone middleware spawning a process to run an openssl command to validate the input (the Keystone token). Something like:

openssl cms -verify -certfile /tmp/keystone-signing-OFShms/signing_cert.pem -CAfile /tmp/keystone-signing-OFShms/cacert.pem -inform PEM -nosmimecap -nodetach -nocerts -noattr << EOF
-----BEGIN CMS-----
-----END CMS-----

One has to pay attention to the purposes of the signing certificate. If its purposes are wrong, tokens generated by Keystone won’t be validated by Keystone clients (middleware). This is reflected in the logs with an error message that typically looks like this:

2015-04-15 18:52:13.027 29533 WARNING keystoneclient.middleware.auth_token [-] Verify error: Command 'openssl' returned non-zero exit status 4
2015-04-15 18:52:13.027 29533 DEBUG keystoneclient.middleware.auth_token [-] Token validation failure. _validate_user_token /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:836
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token Traceback (most recent call last):
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 823, in _validate_user_token
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token verified = self.verify_signed_token(user_token)
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 1258, in verify_signed_token
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token if self.is_signed_token_revoked(signed_text):
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 1216, in is_signed_token_revoked
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token revocation_list = self.token_revocation_list
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 1312, in token_revocation_list
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token self.token_revocation_list = self.fetch_revocation_list()
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 1358, in fetch_revocation_list
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token return self.cms_verify(data['signed'])
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py", line 1239, in cms_verify
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token self.signing_ca_file_name)
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token File "/usr/lib/python2.6/site-packages/keystoneclient/common/cms.py", line 148, in cms_verify
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token raise e
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token CalledProcessError: Command 'openssl' returned non-zero exit status 4
2015-04-15 18:52:13.027 29533 TRACE keystoneclient.middleware.auth_token
2015-04-15 18:52:13.028 29533 DEBUG keystoneclient.middleware.auth_token [-] Marking token as unauthorized in cache _cache_store_invalid /usr/lib/python2.6/site-packages/keystoneclient/middleware/auth_token.py:1154
2015-04-15 18:52:13.028 29533 WARNING keystoneclient.middleware.auth_token [-] Authorization failed for token
2015-04-15 18:52:13.029 29533 INFO keystoneclient.middleware.auth_token [-] Invalid user token - deferring reject downstream

Tor with Brew in Mac OS X

To install the Tor service using Brew in Mac OS X:

$ brew install tor torsocks

However, this does not load the Tor service automatically (either manually or automatically at log in). Since I don’t link things to be loaded automatically for me, I’ve created the following shell script to load or unload (start or stop) the Tor service manually in Mac OS X:


function usage() {
  echo "usage: $0 start|stop";
  exit 1;

function tor_service() {
  launchctl $1 /usr/local/opt/tor/homebrew.mxcl.tor.plist

function start() {
  echo "$0: starting tor service...";
  tor_service load

function stop() {
  echo "$0: stopping tor service...";
  tor_service unload

function check() {
  echo "$0: checking if tor works...";
  if torsocks curl -s https://check.torproject.org | grep -q 'Congratulations. This browser is configured to use Tor.'; then
    echo 'The tor service works';
    echo 'The tor service does NOT work';

case "$1" in




    echo "error: missing or unrecognized command-line argument";

To start (load) the Tor service:

./tor.sh start

To stop (unload) the Tor service:

./tor.sh start

To check whether the Tor service is working:

./tor.sh check

To tor-ify command-line tools like curl or wget:

torsocks wget https://check.torproject.org/