6 Devops interview questions

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Devops is in serious demand these days. At every meetup or tech event I attend, I hear a recruiter or startup founder talking about it. It seems everyone wants to see benefits of talented operations brought to their business.

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That said the skill set is very broad, which explains why there aren’t more devs picking up the batton.





I thought it would be helpful to put together a list of interview questions. There are certainly others, but here’s what I came up with.

1. Explain the gitflow release process

As a devops engineer you should have a good foundation about software delivery. With that you should understand git very well, especially the standard workflow.

Although there are other methods to manage code, one solid & proven method is gitflow. In a nutshell you have two main branches, development & master. Developers checkout a new branch to add a feature, and push it back to development branch. Your stage server can be built automatically off of this branch.

Periodically you will want to release a new version of the software. For this you merge development to master. UAT is then built automatically off of the master branch. When acceptance testing is done, you deploy off of master to production. Hence the saying always ship trunk.

Bonus points if you know that hotfixes are done directly off the master branch & pushed straight out that way.

Related: 8 questions to ask an AWS expert

2. How do you provision resources?

There are a lot of tools in the devops toolbox these days. One that is great at provisioning resources is Terraform. With it you can specify in declarative code everything your application will need to run in the cloud. From IAM users, roles & groups, dynamodb tables, rds instances, VPCs & subnets, security groups, ec2 instances, ebs volumes, S3 buckets and more.

You may also choose to use CloudFormation of course, but in my experience terraform is more polished. What’s more it supports multi-cloud. Want to deploy in GCP or Azure, just port your templates & you’re up and running in no time.

It takes some time to get used to the new workflow of building things in terraform rather than at the AWS cli or dashboard, but once you do you’ll see benefits right away. You gain all the advantages of versioning code we see with other software development. Want to rollback, no problem. Want to do unit tests against your infrastructure? You can do that too!

Related: Does a 4-letter-word divide dev & ops?

3. How do you configure servers?

The four big choices for configuration management these days are Ansible, Salt, Chef & Puppet. For my money Ansible has some nice advantages.

First it doesn’t require an agent. As long as you have SSH access to your box, you can manage it with Ansible. Plus your existing shell scripts are pretty easy to port to playbooks. Ansible also does not require a server to house your playbooks. Simply keep them in your git repository, and checkout to your desktop. Then run ansible-playbook on the yaml file. Voila, server configuration!

Related: How to hire a developer that doesn’t suck

4. What does testing enable?

Unit testing & integration testing are super import parts of continuous integration. As you automate your tests, you formalize how your site & code should behave. That way when you automate the deployment, you can also automate the test process. Let the software do the drudgework of making sure a new feature hasn’t broken anything on the site.

As you automate more tests, you accelerate the software development process, because you’re doing less and less manually. That means being more agile, and makes the business more nimble.

Related: Is AWS too complex for small dev teams?

5. Explain a use case for Docker

Docker a low overhead way to run virtual machines on your local box or in the cloud. Although they’re not strictly distinct machines, nor do they need to boot an OS, they give you many of those benefits.

Docker can encapsulate legacy applications, allowing you to deploy them to servers that might not otherwise be easy to setup with older packages & software versions.

Docker can be used to build test boxes, during your deploy process to facilitate continuous integration testing.

Docker can be used to provision boxes in the cloud, and with swarm you can orchestrate clusters too. Pretty cool!

Related: Will Microservices just die already?

6. How is communicating relevant to Devops

Since devops brings a new process of continuous delivery to the organization, it involves some risk. Actually doing things the old way involves more risk in the long term, because things can and will break. With automation, you can recovery quicker from failure.

But this new world, requires a leap of faith. It’s not right for every organization or in every case, and you’ll likely strike a balance from what the devops holy book says, and what your org can tolerate. However inevitably communication becomes very important as you advocate for new ways of doing things.

Related: How do I migrate my skills to the cloud?

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Top questions to ask a devops expert when hiring or preparing for job & interview

xkcd_goodcode
Strip by Randall Munroe; xkcd.com

Whether your a hiring manager, head of HR or recruiter, you are probably looking for a devops expert. These days good ones are not easy to find. The spectrum of tools & technologies is broad. To manage today’s cloud you need a generalist.

Join 33,000 others and follow Sean Hull on twitter @hullsean.

If you’re a devops expert and looking for a job, these are also some essential questions you should have in your pocket. Be able to elaborate on these high level concepts as they’re crucial in todays agile startups.

Check out: 8 questions to ask an aws ec2 expert

Also new: Top questions to ask on a devops expert interview

And: How to hire a developer that doesn’t suck

1. How do you automate deployments?

A. Get your code in version control (git)

Believe it or not there are small 1 person teams that haven’t done this. But even with those, there’s real benefit. Get on it!

B. Evolve to one script push-button deploy (script)

If deploying new code involves a lot of manual steps, move file here, set config there, set variable, setup S3 bucket, etc, then start scripting. That midnight deploy process should be one master script which includes all the logic.

It’s a process to get there, but keep the goal in sight.

C. Build confidence over many iterations (team process & agile)

As you continue to deploy manually with a master script, you’ll iron out more details, contingencies, and problems. Over time You’ll gain confidence that the script does the job.

D. Employ continuous integration Tools to formalize process (CircleCI, Jenkins)

Now that you’ve formalized your deploy in code, putting these CI tools to use becomes easier. Because they’re custom built for you at this stage!

E. 10 deploys per day (long term goal)

Your longer term goal is 10 deploys a day. After you’ve automated tests, team confidence will grow around developers being able to deploy to production. On smaller teams of 1-5 people this may still be only 10 deploys per week, but still a useful benchmark.

Also: Top serverless interview questions for hiring aws lambda experts

2. What is microservices?

Microservices is about two-pizza teams. Small enough that there’s little beaurocracy. Able to be agile, focus on one business function. Iterate quickly without logjams with other business teams & functions.

Microservices interact with each other through APIs, deploy their own components, and use their own isolated data stores.

Function as a service, Amazon Lambda, or serverless computing enables microservices in a huge way.

Related: Which engineering roles are in greatest demand?

3. What is serverless computing?

Serverless computing is a model where servers & infrastructure do not need to be formalized. Only the code is deployed, and the platform, AWS Lambda for example, takes care of instant provisioning of containers & VMs when the code gets called.

Events within the cloud environment, such a file added to S3 bucket, trigger the serverless functions. API Gateway endpoints can also trigger the functions to run.

Authentication services are used for user login & identity management such as Auth0 or Amazon Cognito. The backend data store could be Dynamodb or Google’s Firebase for example.

Read: Can on-demand consulting save startups time & money?

4. What is containerization?

Containers are like faster deploying VMs. They have all the advantages of an image or snapshot of a server. Why is this useful? Because you can containerize your microservices, so each one does one thing. One has a webserver, with specific version of xyz.

Containers can also help with legacy applications, as you isolate older versions & dependencies that those applications still rely on.

Containers enable developers to setup environments quickly, and be more agile.

Also: 30 questions to ask a serverless fanboy

5. What is CloudFormation?

CloudFormation, formalizes all of your cloud infrastructure into json files. Want to add an IAM user, S3 bucket, rds database, or EC2 server? Want to configure a VPC, subnet or access control list? All these things can be formalized into cloudformation files.

Once you’ve started down this road, you can checkin your infrastructure definitions into version control, and manage them just like you manage all your other code. Want to do unit tests? Have at it. Now you can test & deploy with more confidence.

Terraform is an extension of CloudFormation with even more power built in.

Also: What can startups learn from the DYN DNS outage?

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How I use Terraform & Composer to automate wordpress on aws

iRobot1

How I setup wordpress to deploy automatically on aws

You want to make your wordpress site bulletproof? No server outage worries? Want to make it faster & more reliable. And also host on cheaper components?

I was after all these gains & also wanted to kick the tires on some of Amazon’s latest devops offerings. So I plotted a way forward to completely automate the deployment of my blog, hosted on wordpress.

Here’s how!

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The article is divided into two parts…

Deploy a wordpress site on aws – decouple assets (part 1)

In this one I decouple the assets from the website. What do I mean by this? By moving the db to it’s own server or RDS of even simpler management, it means my server can be stopped & started or terminated at will, without losing all my content. Cool.

You’ll also need to decouple your assets. Those are all the files in the uploads directory. Amazon’s S3 offering is purpose built for this use case. It also comes with easy cloudfront integration for object caching, and lifecycle management to give your files backups over time. Cool !

Deploy a wordpress site on aws – automate (part 2)

The second part we move into all the automation pieces. We’ll use PHP’s Composer to manage dependencies. That’s fancy talk for fetching wordpress itself, and all of our plugins.

1. Isolate your config files

Create a directory & put your config files in it.

$ mkdir iheavy
$ cd iheavy
$ touch htaccess
$ touch httpd.conf
$ touch wp-config.php
$ touch a_simple_pingdom_test.php
$ touch composer.json
$ zip -r iheavy-config.zip *
$ aws s3 cp iheavy-config.zip s3://my-config-bucket/

In a future post we’re going to put all these files in version control. Amazon’s CodeCommit is feature compatible with Github, but integrated right into your account. Once you have your files there, you can use CodeDeploy to automatically place files on your server.

We chose to leave this step out, to simplify the server role you need, for your new EC2 webserver instance. In our case it only needs S3 permissions!

Also: When devops means resistance to change

2. Build your terraform script

Terraform is a lot like Vagrant. I wrote a Howto deploy on EC2 with Vagrant article a couple years ago.

The terraform configuration formalizes what you are asking of Amazon’s API. What size instance? Which AMI? What VPC should I launch in? Which role should my instance assume to get S3 access it needs? And lastly how do we make sure it gets the same Elastic IP each time it boots?

All the magic is inside the terraform config.

Here’s what I see:

levanter:~ sean$ cat iheavy.tf

resource "aws_iam_role" "web_iam_role" {
    name = "web_iam_role"
    assume_role_policy = <

And here's what it looks like when I ask terraform to build my infrastructure:

levanter:~ sean$ terraform apply
aws_iam_instance_profile.web_instance_profile: Refreshing state... (ID: web_instance_profile)
aws_iam_role.web_iam_role: Refreshing state... (ID: web_iam_role)
aws_s3_bucket.apps_bucket: Refreshing state... (ID: iheavy)
aws_iam_role_policy.web_iam_role_policy: Refreshing state... (ID: web_iam_role:web_iam_role_policy)
aws_instance.iheavy: Refreshing state... (ID: i-14e92e24)
aws_eip.bar: Refreshing state... (ID: eipalloc-78732a47)
aws_instance.iheavy: Creating...
  ami:                               "" => "ami-1a249873"
  availability_zone:                 "" => ""
  ebs_block_device.#:                "" => ""
  ephemeral_block_device.#:          "" => ""
  iam_instance_profile:              "" => "web_instance_profile"
  instance_state:                    "" => ""
  instance_type:                     "" => "t1.micro"
  key_name:                          "" => "iheavy"
  network_interface_id:              "" => ""
  placement_group:                   "" => ""
  private_dns:                       "" => ""
  private_ip:                        "" => ""
  public_dns:                        "" => ""
  public_ip:                         "" => ""
  root_block_device.#:               "" => ""
  security_groups.#:                 "" => ""
  source_dest_check:                 "" => "true"
  subnet_id:                         "" => "subnet-1f866434"
  tenancy:                           "" => ""
  user_data:                         "" => "ca8a661fffe09e4392b6813fbac68e62e9fd28b4"
  vpc_security_group_ids.#:          "" => "1"
  vpc_security_group_ids.2457389707: "" => "sg-46f0f223"
aws_instance.iheavy: Still creating... (10s elapsed)
aws_instance.iheavy: Still creating... (20s elapsed)
aws_instance.iheavy: Creation complete
aws_eip.bar: Modifying...
  instance: "" => "i-6af3345a"
aws_eip_association.eip_assoc: Creating...
  allocation_id:        "" => "eipalloc-78732a47"
  instance_id:          "" => "i-6af3345a"
  network_interface_id: "" => ""
  private_ip_address:   "" => ""
  public_ip:            "" => ""
aws_eip.bar: Modifications complete
aws_eip_association.eip_assoc: Creation complete

Apply complete! Resources: 2 added, 1 changed, 0 destroyed.

The state of your infrastructure has been saved to the path
below. This state is required to modify and destroy your
infrastructure, so keep it safe. To inspect the complete state
use the `terraform show` command.

State path: terraform.tfstate
levanter:~ sean$ 

Also: Is Amazon too big to fail?

3. Use Composer to automate wordpress install

There is a PHP package manager called composer. It manages dependencies and we depend on a few things. First WordPress itself, and second the various plugins we have installed.

The file is a JSON file. Pretty vanilla. Have a look:

{
    "name": "acme/brilliant-wordpress-site",
    "description": "My brilliant WordPress site",
    "repositories":[
        {
            "type":"composer",
            "url":"https://wpackagist.org"
        }
    ],
    "require": {
       "aws/aws-sdk-php":"*",
	    "wpackagist-plugin/medium":"1.4.0",
       "wpackagist-plugin/google-sitemap-generator":"3.2.9",
       "wpackagist-plugin/amp":"0.3.1",
	    "wpackagist-plugin/w3-total-cache":"0.9.3",
	    "wpackagist-plugin/wordpress-importer":"0.6.1",
	    "wpackagist-plugin/yet-another-related-posts-plugin":"4.0.7",
	    "wpackagist-plugin/better-wp-security":"5.3.7",
	    "wpackagist-plugin/disqus-comment-system":"2.74",
	    "wpackagist-plugin/amazon-s3-and-cloudfront":"1.1",
	    "wpackagist-plugin/amazon-web-services":"1.0",
	    "wpackagist-plugin/feedburner-plugin":"1.48",
       "wpackagist-theme/hueman":"*",
	    "php": ">=5.3",
	    "johnpbloch/wordpress": "4.6.1"
    },
    "autoload": {
        "psr-0": {
            "Acme": "src/"
        }
    }

}

Read: Is aws a patient that needs constant medication?

4. build your user-data script

This captures all the commands you run once the instance starts. Update packages, install your own, move & configure files. You name it!

#!/bin/sh

yum update -y
yum install emacs -y
yum install mysql -y
yum install php -y
yum install git -y
yum install aws-cli -y
yum install gd -y
yum install php-gd -y
yum install ImageMagick -y
yum install php-mysql -y


yum install -y httpd24 
service httpd start
chkconfig httpd on

# configure mysql password file
echo "[client]" >> /root/.my.cnf
echo "host=my-rds.ccccjjjjuuuu.us-east-1.rds.amazonaws.com" >> /root/.my.cnf
echo "user=root" >> /root/.my.cnf
echo "password=abc123" >> /root/.my.cnf


# install PHP composer
export COMPOSE_HOME=/root
echo "installing composer..."
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php -r "if (hash_file('SHA384', 'composer-setup.php') === 'e115a8dc7871f15d853148a7fbac7da27d6c0030b848d9b3dc09e2a0388afed865e6a3d6b3c0fad45c48e2b5fc1196ae') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
php composer-setup.php
php -r "unlink('composer-setup.php');"
mv composer.phar /usr/local/bin/composer


# fetch config files from private S3 folder
aws s3 cp s3://iheavy-config/iheavy_files.zip .

# unzip files
unzip iheavy_files.zip 

# use composer to get wordpress & plugins
composer update

# move wordpress software
mv wordpress/* /var/www/html/

# move plugins
mv wp-content/plugins/* /var/www/html/wp-content/plugins/

# move pingdom test
mv a_simple_pingdom_test.php /var/www/html

# move htaccess
mv htaccess /var/www/html/.htaccess

# move httpd.conf
mv iheavy_httpd.conf /etc/httpd/conf.d

# move our wp-config into place
mv wp-config.php /var/www/html

# restart apache
service httpd restart

# allow apache to create uploads & any files inside wp-content
chown apache /var/www/html/wp-content

You can monitor things as they're being installed. Use ssh to reach your new instance. Then as root:

$ tail -f /var/log/cloud-init.log

Related: Does Amazon eat it's own dogfood?

5. Time to test

Visit the domain name you specified inside your /etc/httpd/conf.d/mysite.conf

You have full automation now. Don't believe me? Go ahead & TERMINATE the instance in your aws console. Now drop back to your terminal and do:

$ terraform apply

Terraform will figure out that the resources that *should* be there are missing, and go ahead and build them for you. AGAIN. Fully automated style!

Don't forget your analytics beacon code

Hopefully you remember how your analytics is configured. The beacon code makes an API call everytime a page is loaded. This tells google analytics or other monitoring systems what your users are doing, and how much time they're spending & where.

This typically goes in the header.php file. We'll leave it as an exercise to automate this piece yourself!

Also: Is AWS too complex for small dev teams?

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Marching towards continuous deployment

cute code pipeline

If you’re like a lot of small dev teams & startups, you’ve dreamed of jumping on the continuous deployment train, but still aren’t quite there.

Join 32,000 others and follow Sean Hull on twitter @hullsean.

You’ve got your code in some sort of repository. Now what? As it turns out the concepts aren’t terribly complicated. The hardest part is figuring out the process that works for your team.

1. Make a single script for deployment

Can you build easily? You want to take steps to simplify the build process & work towards everything being done from a single script. This might be an ant or maven script. It might be rake if you’re using ruby. Or it might be a makefile. Either way it organizes dependencies, checks your system & compiles things if necessary.

Also: Do startups need techops?

2. Do nightly builds

If you’re currently doing manual builds, work towards doing them nightly. Once you have that under your belt you can actually schedule these to happen automatically every night. But you’re not there yet. You want to work to improve the build process first. Work on the performance of this process. Quality is also important. Is the build quality poor?

Related: Is there a devops talent gap?

3. Is your build process slow?

If it takes a long time to do the build, it takes a long time to get to the point where you can smoke test. You want to shorten this time, so you can iterate faster. Look at ways to improve the overall performance of the whole chain. What’s it getting stuck on?

Read: 3 things devops can learn from aviation

4. Is your build quality poor?

Your tests are going to verify application functionality, do security checks, performance or even compliance checks. If these are often failing, you need dig in to find the source of your trouble. Tests aren’t specific enough? Or are you passing your tests, but finding a lot of bugs in QA?

It may take your team some time to get better at building the right tests, and reducing the bugs that show up in QA. But this will be crucial to increasing confidence level, where you’ll be ready to automate the whole pipeline. As you become more confident in your tests, then you’ll be confident to automatically deploy to production.

Also: How to deploy on Amazon EC2 with Vagrant

5. Evaluate tools to help

Continuous deployment is a lot about process. Once you’ve gotten a handle on that, you’ll have a much better idea of what you want out of the tools. Amazon’s own CodePipeline is one possible build server you can use. Because it’s a service, it’s one less server you don’t have to manage. And of course Jenkins is a popular option. Even with Jenkins there is a service based offering from CloudBees. You might also take a look at CircleCI, & Travis which are newer service based offerings, which although they don’t have all the plugins & integrations of Jenkins, they’ve learned from bumps in the road, and improved the formula.

We like CircleCI because it’s open source, smaller footprint than Jenkins, integrates with Slack & Hipchat, and has Docker support as well.

Also: 5 Tips for better database change management

Get more. Grab our exclusive monthly Scalable Startups. We share tips and special content. Our latest Why I don’t work with recruiters