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crazylion lee

Bcfg2 - 0 views

bcfg2.org

sysadmin server system

shared by crazylion lee on 08 Oct 16 - No Cached
  • crazylion lee on 08 Oct 16
     
    "Bcfg2 helps system administrators produce a consistent, reproducible, and verifiable description of their environment, and offers visualization and reporting tools to aid in day-to-day administrative tasks. It is the fifth generation of configuration management tools developed in the Mathematics and Computer Science Division of Argonne National Laboratory. "
張 旭

Ask HN: What are the best practises for using SSH keys? | Hacker News - 0 views

news.ycombinator.com/item

security ssh key server

shared by 張 旭 on 14 Oct 16 - No Cached
  • Make sure you use full disk encryption and never stand up from your machine without locking it, and make sure you keep your local machine patched.
  • I'm more focused on just stealing your keys from you regardless of length
  • attacks that aren't after your keys specifically, e.g. your home directory gets stolen.
  • ...19 more annotations...
  • ED25519 is more vulnerable to quantum computation than is RSA
  • best practice to be using a hardware token
  • to use a yubikey via gpg: with this method you use your gpg subkey as an ssh key
  • sit down and spend an hour thinking about your backup and recovery strategy first
  • never share a private keys between physical devices
  • allows you to revoke a single credential if you lose (control over) that device
  • If a private key ever turns up on the wrong machine, you *know* the key and both source and destination machines have been compromised.
  • centralized management of authentication/authorization
  • I have setup a VPS, disabled passwords, and setup a key with a passphrase to gain access. At this point my greatest worry is losing this private key, as that means I can't access the server.What is a reasonable way to backup my private key?
  • a mountable disk image that's encrypted
  • a system that can update/rotate your keys across all of your servers on the fly in case one is compromised or assumed to be compromised.
  • different keys for different purposes per client device
  • fall back to password plus OTP
  • relying completely on the security of your disk, against either physical or cyber.
  • It is better to use a different passphrase for each key but it is also less convenient unless you're using a password manager (personally, I'm using KeePass)
  • - RSA is pretty standard, and generally speaking is fairly secure for key lengths >=2048. RSA-2048 is the default for ssh-keygen, and is compatible with just about everything.
  • public-key authentication has somewhat unexpected side effect of preventing MITM per this security consulting firm
  • Disable passwords and only allow keys even for root with PermitRootLogin without-password
  • You should definitely use a different passphrase for keys stored on separate computers,
  • 張 旭 on 14 Oct 16
     
    "Make sure you use full disk encryption and never stand up from your machine without locking it, and make sure you keep your local machine patched"
crazylion lee

Laptop USB Console Adapter - CV211, ATEN KVM Cables - 0 views

www.aten.com/...cv211

usb console kvm

shared by crazylion lee on 14 Mar 17 - No Cached
  • crazylion lee on 14 Mar 17
     
    " 'Turn your laptop into a mobile console in a few seconds.' The CV211 Laptop USB Console Adapter provides a direct Laptop-to-Computer connection for fast and easy remote desktop access with no software to install. High efficiency in a compact design, the CV211 offers bi-directional file transfers, hotkey macros, video recording and screenshots through a USB 2.0 and VGA composite cable."
張 旭

Deploying Rails Apps, Part 6: Writing Capistrano Tasks - Vladi Gleba - 0 views

vladigleba.com/...art-6-writing-capistrano-tasks

rails capistrano deploy ruby docker devops

shared by 張 旭 on 23 Aug 17 - No Cached
  • we can write our own tasks to help us automate various things.
  • organizing all of the tasks here under a namespace
  • upload a file from our local computer.
  • ...27 more annotations...
  • learn about is SSHKit and the various methods it provides
  • SSHKit was actually developed and released with Capistrano 3, and it’s basically a lower-level tool that provides methods for connecting and interacting with remote servers
  • on(): specifies the server to run on
  • within(): specifies the directory path to run in
  • with(): specifies the environment variables to run with
  • run on the application server
  • within the path specified
  • with certain environment variables set
  • execute(): the workhorse that runs the commands on your server
  • upload(): uploads a file from your local computer to your remote server
  • capture(): executes a command and returns its output as a string
    • 張 旭
      張 旭 on 23 Aug 17
       
      capture 是跑在遠端伺服器上
  • upload() has the bang symbol (!) because that’s how it’s defined in SSHKit, and it’s just a convention letting us know that the method will block until it finishes.
  • But in order to ensure rake runs with the proper environment variables set, we have to use rake as a symbol and pass db:seed as a string
  • This format will also be necessary whenever you’re running any other Rails-specific commands that rely on certain environment variables being set
  • I recommend you take a look at SSHKit’s example page to learn more
  • make sure we pushed all our local changes to the remote master branch
  • run this task before Capistrano runs its own deploy task
  • actually creates three separate tasks
  • I created a namespace called deploy to contain these tasks since that’s what they’re related to.
  • we’re using the callbacks inside a namespace to make sure Capistrano knows which tasks the callbacks are referencing.
  • custom recipe (a Capistrano term meaning a series of tasks)
  • /shared: holds files and directories that persist throughout deploys
  • When you run cap production deploy, you’re actually calling a Capistrano task called deploy, which then sequentially invokes other tasks
  • your favorite browser (I hope it’s not Internet Explorer)
  • Deployment is hard and takes a while to sink in.
  • the most important thing is to not get discouraged
  • I didn’t want other people going through the same thing
張 旭

ALB vs ELB | Differences Between an ELB and an ALB on AWS | Sumo Logic - 0 views

www.sumologic.com/...aws-elb-alb

aws HA proxy

shared by 張 旭 on 06 Apr 21 - No Cached
  • If you use AWS, you have two load-balancing options: ELB and ALB.
  • An ELB is a software-based load balancer which can be set up and configured in front of a collection of AWS Elastic Compute (EC2) instances.
  • The load balancer serves as a single entry point for consumers of the EC2 instances and distributes incoming traffic across all machines available to receive requests.
  • ...14 more annotations...
  • the ELB also performs a vital role in improving the fault tolerance of the services which it fronts.
  • he Open Systems Interconnection Model, or OSI Model, is a conceptual model which is used to facilitate communications between different computing systems.
  • Layer 1 is the physical layer, and represents the physical medium across which the request is sent.
  • Layer 2 describes the data link layer
  • Layer 3 (the network layer)
  • Layer 7, which serves the application layer.
  • The Classic ELB operates at Layer 4. Layer 4 represents the transport layer, and is controlled by the protocol being used to transmit the request.
  • A network device, of which the Classic ELB is an example, reads the protocol and port of the incoming request, and then routes it to one or more backend servers.
  • the ALB operates at Layer 7. Layer 7 represents the application layer, and as such allows for the redirection of traffic based on the content of the request.
  • Whereas a request to a specific URL backed by a Classic ELB would only enable routing to a particular pool of homogeneous servers, the ALB can route based on the content of the URL, and direct to a specific subgroup of backing servers existing in a heterogeneous collection registered with the load balancer.
  • The Classic ELB is a simple load balancer, is easy to configure
  • As organizations move towards microservice architecture or adopt a container-based infrastructure, the ability to merely map a single address to a specific service becomes more complicated and harder to maintain.
  • the ALB manages routing based on user-defined rules.
  • oute traffic to different services based on either the host or the content of the path contained within that URL.
張 旭

What is Kubernetes Ingress? | IBM - 0 views

www.ibm.com/...kubernetes-ingress

kubernetes networking

shared by 張 旭 on 27 Aug 21 - No Cached
  • expose an application to the outside of your Kubernetes cluster,
  • ClusterIP, NodePort, LoadBalancer, and Ingress.
  • A service is essentially a frontend for your application that automatically reroutes traffic to available pods in an evenly distributed way.
  • ...23 more annotations...
  • Services are an abstract way of exposing an application running on a set of pods as a network service.
  • Pods are immutable, which means that when they die, they are not resurrected. The Kubernetes cluster creates new pods in the same node or in a new node once a pod dies. 
  • A service provides a single point of access from outside the Kubernetes cluster and allows you to dynamically access a group of replica pods. 
  • For internal application access within a Kubernetes cluster, ClusterIP is the preferred method
  • To expose a service to external network requests, NodePort, LoadBalancer, and Ingress are possible options.
  • Kubernetes Ingress is an API object that provides routing rules to manage external users' access to the services in a Kubernetes cluster, typically via HTTPS/HTTP.
  • content-based routing, support for multiple protocols, and authentication.
  • Ingress is made up of an Ingress API object and the Ingress Controller.
  • Kubernetes Ingress is an API object that describes the desired state for exposing services to the outside of the Kubernetes cluster.
  • An Ingress Controller reads and processes the Ingress Resource information and usually runs as pods within the Kubernetes cluster.  
  • If Kubernetes Ingress is the API object that provides routing rules to manage external access to services, Ingress Controller is the actual implementation of the Ingress API.
  • The Ingress Controller is usually a load balancer for routing external traffic to your Kubernetes cluster and is responsible for L4-L7 Network Services. 
  • Layer 7 (L7) refers to the application level of the OSI stack—external connections load-balanced across pods, based on requests.
  • if Kubernetes Ingress is a computer, then Ingress Controller is a programmer using the computer and taking action.
  • Ingress Rules are a set of rules for processing inbound HTTP traffic. An Ingress with no rules sends all traffic to a single default backend service. 
  • the Ingress Controller is an application that runs in a Kubernetes cluster and configures an HTTP load balancer according to Ingress Resources.
  • The load balancer can be a software load balancer running in the cluster or a hardware or cloud load balancer running externally.
  • ClusterIP is the preferred option for internal service access and uses an internal IP address to access the service
  • A NodePort is a virtual machine (VM) used to expose a service on a Static Port number.
  • a NodePort would be used to expose a single service (with no load-balancing requirements for multiple services).
  • Ingress enables you to consolidate the traffic-routing rules into a single resource and runs as part of a Kubernetes cluster.
  • An application is accessed from the Internet via Port 80 (HTTP) or Port 443 (HTTPS), and Ingress is an object that allows access to your Kubernetes services from outside the Kubernetes cluster. 
  • To implement Ingress, you need to configure an Ingress Controller in your cluster—it is responsible for processing Ingress Resource information and allowing traffic based on the Ingress Rules.
crazylion lee

Publication Listing - 0 views

matterhorn.dce.harvard.edu/...index.html

Data Science computer

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    "Data Science"
crazylion lee

Category Theory for the Sciences - 0 views

category-theory.mitpress.mit.edu/chapter001.html

computer Science

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    "The diagram in Figure 1.1 is intended to evoke thoughts of the scientific method. "
crazylion lee

Realtime Multi-Person 2D Pose Estimation using Part Affinity Fields - 0 views

www.gitxiv.com/...estimation-using-part-affinity

pose 2d programming computer Science

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    "We present a realtime approach for multi-person 2D pose estimation that predicts vector fields, which we refer to as Part Affinity Fields (PAFs), that directly expose the association between anatomical parts in an image. The architecture is designed to jointly learn part locations and their association, via two branches of the same sequential prediction process."
crazylion lee

Jupyter Notebook Viewer - 0 views

nbviewer.jupyter.org/...Advent%20of%20Code.ipynb

computer programming Science python

shared by crazylion lee on 30 Jan 17 - No Cached
  • crazylion lee on 30 Jan 17
     
    "Advent of Code Solutions"
crazylion lee

Flood fill - Wikipedia - 0 views

en.wikipedia.org/Flood_fill

computer programming Science algorithm fill

shared by crazylion lee on 30 Jan 17 - Cached
  • crazylion lee on 30 Jan 17
     
    "Flood fill, also called seed fill, is an algorithm that determines the area connected to a given node in a multi-dimensional array. It is used in the "bucket" fill tool of paint programs to fill connected, similarly-colored areas with a different color, and in games such as Go and Minesweeper for determining which pieces are cleared. When applied on an image to fill a particular bounded area with color, it is also known as boundary fill."
張 旭

Serverless Architectures - 0 views

martinfowler.com/...serverless.html

development architecture system server backend

shared by 張 旭 on 12 Jul 16 - No Cached
  • Serverless was first used to describe applications that significantly or fully depend on 3rd party applications / services (‘in the cloud’) to manage server-side logic and state.
  • ‘rich client’ applications (think single page web apps, or mobile apps) that use the vast ecosystem of cloud accessible databases (like Parse, Firebase), authentication services (Auth0, AWS Cognito), etc.
  • ‘(Mobile) Backend as a Service’
  • ...33 more annotations...
  • Serverless can also mean applications where some amount of server-side logic is still written by the application developer but unlike traditional architectures is run in stateless compute containers that are event-triggered, ephemeral (may only last for one invocation), and fully managed by a 3rd party.
  • ‘Functions as a service
  • AWS Lambda is one of the most popular implementations of FaaS at present,
  • A good example is Auth0 - they started initially with BaaS ‘Authentication as a Service’, but with Auth0 Webtask they are entering the FaaS space.
  • a typical ecommerce app
  • a backend data-processing service
  • with zero administration.
  • FaaS offerings do not require coding to a specific framework or library.
  • Horizontal scaling is completely automatic, elastic, and managed by the provider
  • Functions in FaaS are triggered by event types defined by the provider.
  • a FaaS-supported message broker
  • from a deployment-unit point of view FaaS functions are stateless.
  • allowed the client direct access to a subset of our database
  • deleted the authentication logic in the original application and have replaced it with a third party BaaS service
  • The client is in fact well on its way to becoming a Single Page Application.
  • implement a FaaS function that responds to http requests via an API Gateway
  • port the search code from the Pet Store server to the Pet Store Search function
  • replaced a long lived consumer application with a FaaS function that runs within the event driven context
  • server applications - is a key difference when comparing with other modern architectural trends like containers and PaaS
  • the only code that needs to change when moving to FaaS is the ‘main method / startup’ code, in that it is deleted, and likely the specific code that is the top-level message handler (the ‘message listener interface’ implementation), but this might only be a change in method signature
  • With FaaS you need to write the function ahead of time to assume parallelism
  • Most providers also allow functions to be triggered as a response to inbound http requests, typically in some kind of API gateway
  • you should assume that for any given invocation of a function none of the in-process or host state that you create will be available to any subsequent invocation.
  • FaaS functions are either naturally stateless
  • store state across requests or for further input to handle a request.
  • certain classes of long lived task are not suited to FaaS functions without re-architecture
  • if you were writing a low-latency trading application you probably wouldn’t want to use FaaS systems at this time
  • An API Gateway is an HTTP server where routes / endpoints are defined in configuration and each route is associated with a FaaS function.
  • API Gateway will allow mapping from http request parameters to inputs arguments for the FaaS function
  • API Gateways may also perform authentication, input validation, response code mapping, etc.
  • the Serverless Framework makes working with API Gateway + Lambda significantly easier than using the first principles provided by AWS.
  • Apex - a project to ‘Build, deploy, and manage AWS Lambda functions with ease.'
  • 'Serverless' to mean the union of a couple of other ideas - 'Backend as a Service' and 'Functions as a Service'.
crazylion lee

An integer formula for Fibonacci numbers - Paul's blog - Programming, Computer Science,... - 0 views

paulhankin.github.io/Fibonacci

Fibonacci math

shared by crazylion lee on 10 Jul 16 - No Cached
  • crazylion lee on 10 Jul 16
     
    "Fibonacci"
張 旭

Getting Started with Docker - Servers for Hackers - 0 views

serversforhackers.com/getting-started-with-docker

docker system virtualization

shared by 張 旭 on 30 Apr 15 - No Cached
  • Docker is an isolated portion of the host computer, sharing the host kernel (OS) and even its bin/libraries if appropriate.
  • the Docker Container contains the parts that make Ubuntu different from CoreOS.
  • A Docker container only stays alive as long as there is an active process being run in it.
  • ...10 more annotations...
  • Allocate a (pseudo) tty
  • Keep stdin open (so we can interact with it)
  • Docker allows us make changes to an image, commit those changes, and then push those changes out somehwere.
  • Docker tracks any changes we make to a container
  • The Dockerfile provides a set of instructions for Docker to run on a container.
  • what image (and tag in this case) to base this off of
  • run the given command (as user "root")
  • copy a file from the host machine into the container
  • expose a port to the host machine. You can expose multiple ports
  • run a command
張 旭

Developing with Docker - 1 views

engineering.ifttt.com/...developing-with-docker

shared by 張 旭 on 04 Dec 15 - No Cached
  • Before moving our production infrastructure over however, we decided that we wanted to start developing with them locally first. We could shake out any issues with our applications before risking the production environment.
  • using Chef and Vagrant to provision local VMs
  • Engineers at IFTTT currently all use Apple computers
  • ...7 more annotations...
  • /bin/true
    • 張 旭
      張 旭 on 04 Dec 15
       
      如果使用 docker create 就不用跑這個， 不過目前 docker-compose 沒有支援 volume-only 的 container
  • it will install gems onto the data volume from the bundler-cache container.
  • dev rm bundler-cache
    • 張 旭
      張 旭 on 04 Dec 15
       
      要完全刪除干淨，後面的指令可能是： docker rm -v bundler-cache
  • if you accidentally delete bundler-cache, you then have to install all your gems over again.
  • Containerization and Docker are powerful tools in your infrastructure toolbox.
  • highly recommend starting off in your developer environment first
  • the onboarding time for new developers go from a couple days or more to a matter of hours.
crazylion lee

SSH: Best practices at Aris' Blog - Computers, ssh and rock'n roll - 0 views

blog.0xbadc0de.be/300

SSH security best-practices

shared by crazylion lee on 29 Mar 16 - No Cached
  • crazylion lee on 29 Mar 16
     
    "SSH: Best practices"
張 旭

Introduction to CI/CD with GitLab | GitLab - 0 views

docs.gitlab.com/...index.html

devops CI

shared by 張 旭 on 16 Apr 19 - No Cached
  • deploying code changes at every small iteration, reducing the chance of developing new code based on bugged or failed previous versions
  • based on automating the execution of scripts to minimize the chance of introducing errors while developing applications.
  • For every push to the repository, you can create a set of scripts to build and test your application automatically, decreasing the chance of introducing errors to your app.
  • ...5 more annotations...
  • checked automatically but requires human intervention to manually and strategically trigger the deployment of the changes.
  • instead of deploying your application manually, you set it to be deployed automatically.
  • .gitlab-ci.yml, located in the root path of your repository
  • all the scripts you add to the configuration file are the same as the commands you run on a terminal in your computer.
  • GitLab will detect it and run your scripts with the tool called GitLab Runner, which works similarly to your terminal.
  • 張 旭 on 16 Apr 19
     
    "deploying code changes at every small iteration, reducing the chance of developing new code based on bugged or failed previous versions"
張 旭

Pods - Kubernetes - 0 views

kubernetes.io/...pod

kubernetes pod system

shared by 張 旭 on 05 Jul 19 - No Cached
  • Pods are the smallest deployable units of computing
  • A Pod (as in a pod of whales or pea pod) is a group of one or more containersA lightweight and portable executable image that contains software and all of its dependencies. (such as Docker containers), with shared storage/network, and a specification for how to run the containers.
  • A Pod’s contents are always co-located and co-scheduled, and run in a shared context.
  • ...32 more annotations...
  • A Pod models an application-specific “logical host”
  • application containers which are relatively tightly coupled
  • being executed on the same physical or virtual machine would mean being executed on the same logical host.
  • The shared context of a Pod is a set of Linux namespaces, cgroups, and potentially other facets of isolation
  • Containers within a Pod share an IP address and port space, and can find each other via localhost
  • Containers in different Pods have distinct IP addresses and can not communicate by IPC without special configuration. These containers usually communicate with each other via Pod IP addresses.
  • Applications within a Pod also have access to shared volumesA directory containing data, accessible to the containers in a pod. , which are defined as part of a Pod and are made available to be mounted into each application’s filesystem.
  • a Pod is modelled as a group of Docker containers with shared namespaces and shared filesystem volumes
    • 張 旭
      張 旭 on 05 Jul 19
       
      類似 docker-compose 裡面宣告的同一坨？
  • Pods are considered to be relatively ephemeral (rather than durable) entities.
  • Pods are created, assigned a unique ID (UID), and scheduled to nodes where they remain until termination (according to restart policy) or deletion.
  • it can be replaced by an identical Pod
  • When something is said to have the same lifetime as a Pod, such as a volume, that means that it exists as long as that Pod (with that UID) exists.
  • uses a persistent volume for shared storage between the containers
  • Pods serve as unit of deployment, horizontal scaling, and replication
  • The applications in a Pod all use the same network namespace (same IP and port space), and can thus “find” each other and communicate using localhost
  • flat shared networking space
  • Containers within the Pod see the system hostname as being the same as the configured name for the Pod.
  • Volumes enable data to survive container restarts and to be shared among the applications within the Pod.
  • Individual Pods are not intended to run multiple instances of the same application
  • The individual containers may be versioned, rebuilt and redeployed independently.
  • Pods aren’t intended to be treated as durable entities.
  • Controllers like StatefulSet can also provide support to stateful Pods.
  • When a user requests deletion of a Pod, the system records the intended grace period before the Pod is allowed to be forcefully killed, and a TERM signal is sent to the main process in each container.
  • Once the grace period has expired, the KILL signal is sent to those processes, and the Pod is then deleted from the API server.
  • grace period
  • Pod is removed from endpoints list for service, and are no longer considered part of the set of running Pods for replication controllers.
  • When the grace period expires, any processes still running in the Pod are killed with SIGKILL.
  • By default, all deletes are graceful within 30 seconds.
  • You must specify an additional flag --force along with --grace-period=0 in order to perform force deletions.
  • Force deletion of a Pod is defined as deletion of a Pod from the cluster state and etcd immediately.
  • StatefulSet Pods
  • Processes within the container get almost the same privileges that are available to processes outside a container.
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