339 lines
8.8 KiB
Markdown
339 lines
8.8 KiB
Markdown
# DevOps Interview Questions
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## Table of Contents
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1. [Jenkins](#jenkins)
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1. [AWS](#aws)
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1. [Network](#network)
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1. [Linux](#linux)
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1. [Ansible](#ansible)
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1. [Docker](#docker)
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1. [Python](#python)
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1. [Prometheus](#prometheus)
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## Jenkins
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###### beginner
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* Explain what is Jenkins and what is it used for
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* Explain each of the following in the context of nodes:
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* Master
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* Slave
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* Executor
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* Agent
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* Label
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* Explain each of the following in context of jobs:
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* Job
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* Build
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* Test
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* Artifacts
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* Explain the architecture of Jenkins
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* What are the different ways to trigger a build?
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* How do you start a build automatically upon a change in a certain repository?
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* What is a plugin?
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* What plugins are you using in Jenkins? Which do you consider to most useful?
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* Installation questions
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* How to install Jenkins?
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* How to install a plugin?
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* How to install an agent?
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###### Intermediate
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- What type of jobs there are?
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- How do you notify users on build results?
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- Can also be asked like that: what ways there are to notify users on build results?
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###### Advanced
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* Write a script to remove all the jobs which include the string "REMOVE_ME"
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## AWS
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###### Global Infrastructure
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- Explain the following
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- Availability zone
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- Region
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- Edge location
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###### S3 - beginner questions
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- Explain what is S3 and what is it used for
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- What is a bucket?
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- True or False? a bucket name must be globally unique
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- What objects in S3 consists of?
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- Another way to ask it: explain key, value, version id and metadata in context of objects
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- Explain data consistency
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- Can you host dynamic websites on s3? what about static websites?
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###### CloudFront
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- Explain what is CloudFront and what is it used for
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- Explain the following
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- Origin
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- Edge location
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- Distribution
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- What delivery methods available for the user with CDN?
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- True or False? object are cached for the life of TTL
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## Network
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Network questions can be found [here](https://github.com/bregman-arie/computer-networking/blob/master/interview_questions/README.md)
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## Linux
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* What is the different between a soft link and hard link?
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```
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hard link is the same file, using the same inode.
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soft link is a shortcut to another file, using a different inode.
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soft links can be created between different file systems while
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hard link can be created only within the same file system.
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```
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* How to run a process in background and why to do that in the first place?
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```
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You can achieve that by specifying & at end of the command.
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As to Why? since some commands/processes can take a lot of time to finish
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execution or run forever
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```
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* What signal is used when you run 'kill <process id>'?
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```
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The default signal is SIGTERM (15). This signal kills
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process gracefully which means it allows it to save current
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state configuration.
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```
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* What signals are you familiar with?
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```
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SIGTERM - default signal for terminating a process
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SIGHUP - common usage is for reloading configuration
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SIGKILL - a signal which cannot caught or ignored
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To view all available signals run `kill -l`
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```
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## Ansible
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* Describe each of the following components in Ansible, including the relationship between them:
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* Task
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* Module
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* Play
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* Playbook
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* Role
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```
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Task – a call to a specific Ansible module
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Module – the actual unit of code executed by Ansible on your own host or a remote host. Modules are indexed by category (database, file, network, …) and also referred as task plugins.
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Play – One or more tasks executed on a given host(s)
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Playbook – One or more plays. Each play can be executed on the same or different hosts
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Role – Ansible roles allows you to group resources based on certain functionality/service such that they can be easily reused. In a role, you have directories for variables, defaults, files, templates, handlers, tasks, and metadata. You can then use the role by simply specifying it in your playbook.
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```
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* Write a task to create the directory ‘/tmp/new_directory’
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```
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- name: Create a new directory
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file:
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path: "/tmp/new_directory"
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state: directory
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```
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* What would be the result of the following play?
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```
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---
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- name: Print information about my host
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hosts: localhost
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gather_facts: 'no'
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tasks:
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- name: Print hostname
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debug:
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msg: "It's me, {{ ansible_hostname }}"
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```
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```
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When given a written code, always inspect it thoroughly. If your answer is “this will fail” then you are right. We are using a fact (ansible_hostname), which is a gathered piece of information from the host we are running on. But in this case, we disabled facts gathering (gather_facts: no) so the variable would be undefined which will result in failure.
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```
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* Write a playbook to install ‘zlib’ and ‘vim’ on all hosts if the file ‘/tmp/mario’ exists on the system.
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```
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---
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- hosts: all
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vars:
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mario_file: /tmp/mario
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package_list:
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- 'zlib'
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- 'vim'
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tasks:
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- name: Check for mario file
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stat:
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path: "{{ mario_file }}"
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register: mario_f
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- name: Install zlib and vim if mario file exists
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become: "yes"
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package:
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name: "{{ item }}"
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state: present
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with_items: "{{ package_list }}"
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when: mario_f.stat.exists
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```
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* Write a playbook to deploy the file ‘/tmp/system_info’ on all hosts except for controllers group, with the following content
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```
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I'm <HOSTNAME> and my operating system is <OS>
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```
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replace <HOSTNAME> and <OS> with the actual data for the specific host you are running on
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The playbook to deploy the system_info file
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```
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---
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- name: Deploy /tmp/system_info file
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hosts: all:!controllers
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tasks:
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- name: Deploy /tmp/system_info
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template:
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src: system_info.j2
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dest: /tmp/system_info
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```
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The content of the system_info.j2 template
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```
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# {{ ansible_managed }}
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I'm {{ ansible_hostname }} and my operating system is {{ ansible_distribution }
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```
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## Docker
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* What happens when you run `docker run hello-world`?
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```
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Docker CLI passes your request to Docker daemon.
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Docker daemon downloads the image from Docker Hub
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Docker daemon creates a new container by using the image it downloaded
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Docker daemon redirects output from container to Docker CLI which redirects it to the standard output
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```
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* How do you run a container?
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* What do you see when you run `docker ps`?
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* What `docker commit` does? when will you use it?
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* Explain what is Dockerfile used for and the content of the following Dockerfile
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```
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FROM registry.access.redhat.com/rhel7/rhel
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RUN yum -y install httpd && yum -y update; yum clean all
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EXPOSE 80
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ENTRYPOINT [ "/usr/sbin/httpd" ]
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CMD [ "-D", "FOREGROUND" ]
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```
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Answer:
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```
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Use the image 'rhel7/rhel' from the registry 'registry.access.redhat.com` to run httpd.
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Befor running it, install the httpd package, update all packages and expose port 80.
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```
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## Python
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##### beginner
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* What data type supported in Python and which of them are mutable?
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What function can you use to show that a certain data type is mutable?
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```
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The mutable data types are:
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List
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Dictionary
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Set
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The immutable data types are:
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Numbers (int, float, ...)
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String
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Bool
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Tuple
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The id function can be used to check if a given variable is mutable or not.
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```
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* What is PEP8? Give an example of 5 style guidelines
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```
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PEP8 is a list of coding conventions and style guidelines for Python
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5 style guidelines:
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1. Limit all lines to a maximum of 79 characters.
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2. Surround top-level function and class definitions with two blank lines.
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3. Use commas when making a tuple of one element
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4. Use spaces (and not tabs) for indentation
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5. Use 4 spaces per indentation level
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```
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##### Intermediate
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* What _ is used for in Python?
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```
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1. Translation lookup in i18n
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2. Hold the result of the last executed expression or statement
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3. As a general purpose "throwaway" variable name. For example: x, y, _ = get_data() (x and y are used but since we don't care about third variable, we "threw it away").
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```
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* Sort a list of lists by the second item of each nested list
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```
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li = [[1, 4], [2, 1], [3, 9], [4, 2], [4, 5]]
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sorted(x, key=lambda l: l[1])
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```
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* You have the following lists: [{'name': 'Mario', 'food': ['mushrooms', 'goombas']}, {'name': 'Luigi', 'food': ['mushrooms', 'turtles']}]
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Extract all type of foods. Final output should be: {'mushrooms', 'goombas', 'turtles'}
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```
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set([food for bro in x for food in bro['food']])
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```
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## Prometheus
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* Describe the following Prometheus components:
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- Prometheus server
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- Push Gateway
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- Alert Manager
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```
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Prometheus server responsible for scraping the storing the data
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Push gateway is used for short-lived jobs
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Alert manager is responsible for alerts ;)
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```
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* What is an exporter? What is it used for?
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