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Cheat Sheet

Author @Saief1999

Bash scripting​

What we did : We setup an Azure VM, copy the project files through SSH and then run the apps through SSH too.

bash -s : Run commands from standard input

set -e : set the shell to exit as soon as the first error is encountered

set -u: The -u option treats unset or undefined variables except for special parameters such as wildcards (*) or “@” as errors during parameter expansion.

#!/usr/bin/env bash : better than #!/bin/bash because it will always use the right "bash"

to handle the nodejs process , without depending on ssh

  • no-hup
  • pm2 ( or nodemon )
  • forever

envsubst : Subtitute variable in scripts

the problem is , when we close the ssh session, the command that we're executing through ssh will stop ( even if we use & )

The solution is :

  • nohup
  • something for healthcheck / disaster recovery , a process manager ( both of these are used for nodejs ) :
    • pm2
    • forever

forever is able to launch the node process and manage it (through a forever.json), it can also track its logs and the logs of its processes

We can stop & start the application ( so it gets updated after restart )

Ansible​

Ansible is push based.

Chef is pull based, we need an agent to update configuration inside our servers that pull from a cookbook that's inside a repository

Playbook > Tasks > Modules

Ansible roles : Used for reusable playbooks

Bastion hosts : secure host that forward ssh requests to other instances that are private from the outside world

ssh -j <bastion-host> <remote-host>

Vagrant​

vagrant init <box-name> write spec for VM using vagrantfile to create repeatable environment containing our different tools.

images for VMs are avaiable through vagrant boxes

providers for Vagrant:

  • vmware/ docker / hyperv / ...

we can use provisioners to execute commands ( like Ansible, puppet, Chef, Shell )