devops-interview-questions

Repository with DevOps interview questions.

Questions

Programming

• What is your favorite scripting/programming language(s)? Why ?
• General CS, algorithms Q&A: 5 minutes
  • Data structures - discuss possible implementations and applications:
    • Binary tree
    • Hash map
    • Heap
  • Complexity classes - discuss and give examples:
    • Linear
    • Polynomial
    • NP Complete / NP Hard
  • Sorting algorithms - discuss:
    • What is the fastest sorting algorithm?
    • What is the complexity of quick sort?
  • Distributed systems:
    • What’s Paxos?
    • What's Raft?
    • What’s consistent hashing?
  • Hands-on coding:
    • Inverse a string in place

DevOps

• What DevOps is? Why do we need it?
  • Example of answers:
    • Why do we need it?
      • Increase deployment frequency
      • Lower failure rate of new releases
      • Shortened lead time between fixes
      • Faster mean time to recovery in the event of new release crashing
    • What DevOps is?
      • CALMS
      • C – Culture (promotes collaborative and open culture between Dev and Ops)
      • A – Automation (automate wherever applicable)
      • L- Learning (continuous learning & experimentation)
      • M – Measure (Measure with shared metrics across the Dev and ops for better management)
      • S – Sharing (Shared delivery process across Dev and Ops to build , deploy, maintain and monitor product with mentality of One Team – One Goal)
• What is the purpose of a post-mortem meeting?
• What is meant by Continuous Integration?
• What are the success factors for Continuous Integration?
  • Examples of answers:
    • Maintain a code repository
    • Automate the build
    • Make the build self-testing
    • Everyone commits to the baseline every day
    • Every commit (to baseline) should be built
    • Keep the build fast
    • Test in a clone of the production environment
    • Make it easy to get the latest deliverables
    • Everyone can see the results of the latest build
    • Automate deployment
• How would you implement CI (continuous delivery) - end to end, including source control, branches, tools, etc. ?
• What is Continious Delivery? Continious Deployment?
• What is the difference between Continuous Integration, Continious Delivery and Continious Deployment?
• What’s the difference between git and github ? What about git and SVN ?
• What is git rebase?
• In Git how do you revert a commit that has already been pushed and made public?
• What is puppet/chef/ansible used for? What are the advantages over shell scripts ?
• What do you understand by “Infrastructure as code”? How does it fit into the DevOps methodology? What purpose does it achieve?
• How do you give your developers access to the production logs ?
• Tell me about the worst-run/best-run outage you’ve been a part of. What made it bad/well-run?
• How do you monitor your application ? How do you make sure it is working ? How do you get alerts when it stops working ?
• What would be the availability and performance metrics for a key value store ? What about for MySQL replication ?
• How would you deploy software to 5000 systems?
• What is caching ? Where should a large scale application cache, and what data should be cached ?

SysOps

• What is your favorite editor?
• What is RAID? What is RAID0, RAID1, RAID5, RAID10?
• Describe the general file system hierarchy of a Linux system.
• Describe what each of the following command line utilities do:
  • tee
  • awk
  • tr
  • cut
  • curl
  • tail
  • sed
• Command line demo:
  • Search for "my konfu is the best" in all *.py files
  • Replace the occurrence of "my konfu is the best" with "I'm a linux jedi master" in all *.txt files
  • Find all files which have been accessed within the last 30 days
• What is the difference between virtual memory and swap ?
• What is the difference between hardlinks and symlinks?
• What is an inode and what fields are stored in an inode?
• What are zombie processes ?
• Can you have several HTTPS virtual hosts sharing the same IP?
• What is the difference between processes and threads?
• What is the difference between exec and fork?
• How nginx can handle a lot of connections? What does it use inside?
  • Example of answer: Eventloop.
• What is "nohup" used for?
• What is an atomic operation?
• I've added my public ssh key into authorized_keys but I'm still getting a password prompt, what can be wrong?
• How do you catch a SIGHUP ? What about SIGSEGV ? What about SIGKILL ?
• What is the Linux Kernel OOM and how does it work ?
• What's a chroot jail?
• Describe the Linux boot process with as much detail as possible, starting from when the system is powered on and ending when you get a prompt.
• What's LD_PRELOAD and when is it used?
• You ran a binary and nothing happened. How would you debug this?
• When can a socket receive E_AGAIN ?
• What is a dynamically/statically linked file?
• A careless sysadmin executes the following command: chmod 444 /bin/chmod - what do you do to fix this?
• I've lost my root password, what can I do?
• You have accidentally deleted a running script, how could you restore it ?
• What load balancers have you used ?
• AWS:
  • What is the difference between an AMI and an instance ?
  • What’s EBS ? What’s an EBS snapshot ? What is the real cost of having an EBS snapshot ?
  • What’s a VPC ?
  • What’s the difference between a region and an availability zone ?
  • What’s an ELB ?
  • What’s S3 ? What are the features supported on S3 ?

DBA

• What’s ACID ? How is it implemented ?
• What is row level locking ? Table level locking ?
• How do you check which jobs are running?
• Imagine you have a filesystem that supports snapshots - how do you take hot backups using volume managers (LVM/EBS)?
• What is the need for master/slave replication in MySQL ? What about master/master replication ? How does replication work in MySQL ?
• How would you handle DB migrations? How would you automate DB migration process?
• What pros/cons could you tell about MySQL/PostgreSQL?

Networking

• What is IPv6 ? Why should we care?
• How does ping work ? What about traceroute ?
• I type http://www.yahoo.com in my browser’s URL bar and I press enter. What happens ? (discuss at every OSI layer - Physical, data link, network, transport, session, presentation, application)
  • DNS & anycast, IP, UDP, routing, BGP, TCP, HTTP, transparent proxy
  • What is BGP?
  • What’s a PTR in DNS? Why should we care?
• What if I change from http://www.yahoo.com to https://www.yahoo.com ?
  • Public/private certificates, CAs, proxying, MiTM, etc.
• What happens when I press the send button in my email client ?
• How do we prevent bots crawling ? How would you deal with a syn flood ?
• How many hosts in a /24 network? What about a /22 ?
• What is the difference between DNAT and SNAT ? When do you use either ?
• What is a virtual IP address? What is a cluster?
• What is IPv6 ? Why should we care?

General

• What are some of the most common DevOps personality characteristics ?