Cluster Management Made Easy with Ansible

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

Installation¶

sudo pip3 install ansible

Configuration¶

Ansible looks for configuration file in the following order.

ansible.cfg in the current directory.
~/.ansible.cfg
/etc/ansible.cfg

Examples¶

Copy a file to each machine in the cluster.

proxychains ansible all \
    -i hosts \
    --user=stack \
    --private-key=~/.ssh/rsa \
    -m copy \
    -a "src=../pkg.tar.gz dest=~/"

Install an R package on each machine in the cluster.

proxychains ansible all \
    -i hosts \
    --user=stack \
    --private-key=~/.ssh/spot_rsa \
    -a 'Rscript -e "install.packages(\"../pkg.tar.gz\")"'

Host Key Checking¶

Ansible 1.2.1 and later have host key checking enabled by default. If a machine in the cluster is reimaged, it will result in an error message (host fingerprint changed). This can be fixed by removing keys from ~/.ssh/known_hosts. If a machine in the cluster is not in ~/.ssh/known_hosts, it will prompt for confirmation of adding the host as a known one. To avoid those interuptions, you can add the following into your Ansible configuration file.

[defaults]
host_key_checking = False

Alternatively this can be set by an environment variable:

export ANSIBLE_HOST_KEY_CHECKING=False

Also note that host key checking in paramiko mode is slow, therefore switching to ssh is recommended when you have host key checking enabled in Ansible.

References¶

Run Commands on Remote Machines

https://github.com/ansible/ansible

https://serversforhackers.com/running-ansible-programmatically