GOV.UK Fabric Scripts
Fabric is a command-line tool for application deployment and systems administration tasks. It allows the user to run commands across a server farm.
Local usage and environment setup
The tool is intended to be configured and run on your local workstation/laptop. You should use
virtualenv to create an isolated Python environment.
virtualenv and set up the environment:
$ sudo easy_install pip $ sudo pip install virtualenv $ mkdir ~/venv $ virtualenv ~/venv/fabric-scripts
To enable the virtual environment for this session (you will need to do this for each new terminal window):
$ . ~/venv/fabric-scripts/bin/activate
To install the dependencies:
$ pip install -Ur requirements.txt
NB: if you get a "pip: command not found" error, run this first:
$ sudo easy_install pip
Configure it (see the fabric documentation for more examples),
$ echo 'user = jimbob' >> ~/.fabricrc
You can view a list of the available tasks:
$ fab -l
And execute against an environment and set of hosts like so:
$ fab integration all hosts ... $ fab integration class:frontend do:'uname -a' $ fab integration class:cache,bouncer do:uptime ...
Targetting groups of machines
Fabric tasks can be run on groups of machines in a variety of different ways.
By puppet class:
# target all machines that have the 'govuk::safe_to_reboot::yes' class $ fab integration puppet_class:govuk::safe_to_reboot::yes do:'uname -a'
By numeric machine suffix:
# target all machines that end in '2' $ fab integration numbered:2 do:'uname -a'
By node type (as defined in puppet):
# target all 'frontend' machines $ fab integration node_type:frontend do:'uname -a'
By the node name:
# target just one node $ fab production -H backend-3.backend do:'uname -a'
Remote usage (legacy)
It was previously possible to use these scripts from the jumpboxes via the
govuk_fab wrapper. This is no longer supported as it relied on SSH agent
forwarding, which is a Bad Thing because other people with root access to
that jumpbox would be able to re-use any of the private keys in your agent.
You should convert to the [local usage](#Local usage) method described above
and ensure that you do not have the following option anywhere in your
Syncing postgres machines
fab <env> -H '<src_db>' postgresql.sync:<db_name>,<dst_db> -A
the -A must be specified to forward the agent
This will sync the specified database
<db_name> from the machine with the
<src_db> to the machine with hostaname
<dst_db>. It will destroy data on the destination db.