Systems Administration¶
Fabric¶
Fabric is a library for simplifying system administration tasks. While Chef and Puppet tend to focus on managing servers and system libraries, fabric is more focused on application level tasks such as deployment.
Install Fabric:
$ pip install fabric
The following code will create two tasks that we can use: memory_usage and
deploy. The former will output the memory usage on each machine. The
latter will ssh into each server, cd to our project directory, activate the
virtual environment, pull the newest codebase, and restart the application
server.
from fabric.api import cd, env, prefix, run, task
env.hosts = ['my_server1', 'my_server2']
@task
def memory_usage():
run('free -m')
@task
def deploy():
with cd('/var/www/project-env/project'):
with prefix('. ../bin/activate'):
run('git pull')
run('touch app.wsgi')
With the previous code saved in a file named fabfile.py, we can check memory usage with:
$ fab memory_usage
[my_server1] Executing task 'memory'
[my_server1] run: free -m
[my_server1] out: total used free shared buffers cached
[my_server1] out: Mem: 6964 1897 5067 0 166 222
[my_server1] out: -/+ buffers/cache: 1509 5455
[my_server1] out: Swap: 0 0 0
[my_server2] Executing task 'memory'
[my_server2] run: free -m
[my_server2] out: total used free shared buffers cached
[my_server2] out: Mem: 1666 902 764 0 180 572
[my_server2] out: -/+ buffers/cache: 148 1517
[my_server2] out: Swap: 895 1 894
and we can deploy with:
$ fab deploy
Additional features include parallel execution, interaction with remote programs, and host grouping.
Salt¶
Salt is an open source infrastructure management tool. It supports remote command execution from a central point (master host) to multiple hosts (minions). It also supports system states which can be used to configure multiple servers using simple template files.
Salt supports python versions 2.6 and 2.7 and can be installed via pip:
$ pip install salt
After configuring a master server and any number of minion hosts, we can run arbitrary shell commands or use pre-built modules of complex commands on our minions.
The following command lists all available minion hosts, using the ping module.
$ salt '*' test.ping
The host filtering is acomplished by matching the minion id, or using the grains system. The grains system uses static host information like the operating system version or the CPU architecture to provide a host taxonomy for the salt modules.
The following command lists all available minions running CentOS using the grains system:
$ salt -G 'os:CentOS' test.ping
Salt also provides a state system. States can be used to configure the minion hosts.
For example, when a minion host is ordered to read the following state file, will install and start the Apache server:
apache:
pkg:
- installed
service:
- running
State files can be written using YAML, the Jinja2 template system or pure python.
Chef¶
Puppet¶
Blueprint¶
Todo
Write about Blueprint
