DevOps Interview Questions

A development practice where developers integrate code into a shared repository frequently. It can range from a couple of changes every day or a week to a couple of changes in one hour in larger scales.

Each piece of code (change/patch) is verified, to make the change is safe to merge. Today, it's a common practice to test the change using an automated build that makes sure the code can integrated. It can be one build which runs several tests in different levels (unit, functional, etc.) or several separate builds that all or some has to pass in order for the change to be merged into the repository.

In your answer you can mention one or more of the following:

• mature vs. cutting edge
• community size
• architecture aspects - agent vs. agentless, master vs. masterless, etc.

In mutable infrastructure paradigm, changes applied on top of the existing infrastructure and over time the infrastructure builds up a history of changes. Ansible, Puppet and Chef are examples to tools which follow mutable infrastructure paradigm.

In immutable infrastructure paradigm, every change is actually new infrastructure. So a change to a server will result in a new server instead of updating it. Terraform is an example of technology which follows the immutable infrastructure paradigm.

• Archive - collect all your app files into one archive (e.g. tar) and deliver it to the user.
• Package - depends on the OS, you can use your OS package format (e.g. in RHEL/Fefodra it's RPM) to deliver your software with a way to install, uninstall and update it using the standard packager commands
• Images - Either VM or container images where your package is included with everything it needs in order to run successfully.

Stateless applications don't store any data in the host which makes it ideal for horizontal scaling and microservices. Stateful applications depend on the storage to save state and data, typically databases are stateful applications.

Alerts Tickets Logging

One can argue whether it's per company definition or a global one but at least according to a large companies, like Google for example, the SRE team is responsible for availability, latency, performance, efficiency, change management, monitoring, emergency response, and capacity planning of their services

Configuration drift happens when in an environment of servers with the exact same configuration and software, a certain server or servers are being applied with updates or configuration which other servers don't get and over time these servers become slightly different than all others.

This situation might lead to bugs which hard to identify and reproduce.

Note: cross-dependency is when you have two or more changes to separate projects and you would like to test them in mutual build instead of testing each change separately.

• Testing cross-dependencies (changes from multiple projects together)
• Starting builds from any stage (although cloudbees implemented something called checkpoints)

IAAS PAAS SAAS

Edge locations are basically content delivery network which caches data and insures lower latency and faster delivery to the users in any location. They are located in major cities in the world.

Stop the instance, the type of the instance to match the desired RAM and start the instance.

Application: user end (HTTP is here) Presentation: establishes context between application-layer entities (Encryption is here) Session: establishes, manages and terminates the connections Transport: transfers variable-length data sequences from a source to a destination host (TCP & UDP are here) Network: transfers datagrams from one network to another (IP is here) Data link: provides a link between two directly connected nodes (MAC is here) Physical: the electrical and physical spec the data connection (Bits are here)

Unitcast: One to one communication where there is one sender and one reciever.

Broadcast: Sending a message to everone in the network. The address ff:ff:ff:ff:ff:ff is used for broadcasting. Two common protocols which use broadcast are ARP and DHCP.

Multicast: Sending a message to a group of subscribers. It can be one-to-many or many-to-many.

CSMA/CD stands for Carrier Sense Multiple Access / Collision Detection. Its primarily focus it to manage access to shared medium/bus where only one host can transmit at a given point of time.

CSMA/CD algorithm:

1. Before sending a frame, it checks whether another host already transmitting a frame.
2. If no one transmitting, it starts transmitting the frame.
3. If two hosts transmitted at the same time, we have a collision.
4. Both hosts stop sending the frame and they send to everyone a 'jam signal' notifying everyone that a collision occured
5. They are waiting for a random time before sending again
6. Once each host waited for a raondom time, they try to send the frame again and so the

TCP establishes a connection between the client and the server to guarantee the order of the packages, on the other hand, UDP does not establish a connection between client and server and doesn't handle package order. This makes UDP more lightweight than TCP and a perfect candidate for streaming services.

00110011110100011101

You can use the commands cron and at. With cron, tasks are scheduled using the following format:

The tasks are stored in a cron file.

Normally you will schedule batch jobs.