AWS : NTP
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What's NTP?
NTP is a protocol designed to synchronize the clocks of computers over a network.
NTP is a TCP/IP protocol for synchronizing time over a network. Basically a client requests the current time from a server, and uses it to set its own clock. Actually, behind the scene, NPT structure is very complex, however, fortunately, all that complexity is hidden from us.
Picture source : Coursera : Cloud Computing - NTP
ntp daemon - ntpd
The ntp daemon ntpd calculates the drift of our system clock and continuously adjusts it, so there are no large corrections that could lead to inconsistent logs for instance. The cost is a little processing power and memory, but for a modern server this is negligible.
ntp install
To install ntpd, from a terminal prompt enter:
$ sudo apt-get install ntp
ntp Configuration
To configure, we need to edit /etc/ntp.conf to add/remove server lines. By default these servers are configured:
server 0.ubuntu.pool.ntp.org server 1.ubuntu.pool.ntp.org server 2.ubuntu.pool.ntp.org server 3.ubuntu.pool.ntp.org
We may customize the NPT configuration to our region:
server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org server 3.north-america.pool.ntp.org
After changing the config file we have to restart the ntpd:
$ sudo service ntp restart
viewing ntp status
To see more info, we need to issue ntpq:
$ ntpq -np
remote refid st t when poll reach delay offset jitter
==============================================================================
+66.175.209.17 209.51.161.238 2 u 4 128 377 91.340 11.126 2.333
+69.195.142.122 208.75.89.4 3 u 2 128 377 40.737 4.903 1.047
*198.60.22.240 .GPS. 1 u 7 128 377 19.378 6.254 7.289
-54.236.224.171 66.228.35.252 3 u 69 128 377 85.573 1.301 2.325
The line starting with * is the synched NTP server.
AWS (Amazon Web Services)
- AWS : EKS (Elastic Container Service for Kubernetes)
- AWS : Creating a snapshot (cloning an image)
- AWS : Attaching Amazon EBS volume to an instance
- AWS : Adding swap space to an attached volume via mkswap and swapon
- AWS : Creating an EC2 instance and attaching Amazon EBS volume to the instance using Python boto module with User data
- AWS : Creating an instance to a new region by copying an AMI
- AWS : S3 (Simple Storage Service) 1
- AWS : S3 (Simple Storage Service) 2 - Creating and Deleting a Bucket
- AWS : S3 (Simple Storage Service) 3 - Bucket Versioning
- AWS : S3 (Simple Storage Service) 4 - Uploading a large file
- AWS : S3 (Simple Storage Service) 5 - Uploading folders/files recursively
- AWS : S3 (Simple Storage Service) 6 - Bucket Policy for File/Folder View/Download
- AWS : S3 (Simple Storage Service) 7 - How to Copy or Move Objects from one region to another
- AWS : S3 (Simple Storage Service) 8 - Archiving S3 Data to Glacier
- AWS : Creating a CloudFront distribution with an Amazon S3 origin
- AWS : Creating VPC with CloudFormation
- AWS : WAF (Web Application Firewall) with preconfigured CloudFormation template and Web ACL for CloudFront distribution
- AWS : CloudWatch & Logs with Lambda Function / S3
- AWS : Lambda Serverless Computing with EC2, CloudWatch Alarm, SNS
- AWS : Lambda and SNS - cross account
- AWS : CLI (Command Line Interface)
- AWS : CLI (ECS with ALB & autoscaling)
- AWS : ECS with cloudformation and json task definition
- AWS Application Load Balancer (ALB) and ECS with Flask app
- AWS : Load Balancing with HAProxy (High Availability Proxy)
- AWS : VirtualBox on EC2
- AWS : NTP setup on EC2
- AWS: jq with AWS
- AWS & OpenSSL : Creating / Installing a Server SSL Certificate
- AWS : OpenVPN Access Server 2 Install
- AWS : VPC (Virtual Private Cloud) 1 - netmask, subnets, default gateway, and CIDR
- AWS : VPC (Virtual Private Cloud) 2 - VPC Wizard
- AWS : VPC (Virtual Private Cloud) 3 - VPC Wizard with NAT
- DevOps / Sys Admin Q & A (VI) - AWS VPC setup (public/private subnets with NAT)
- AWS - OpenVPN Protocols : PPTP, L2TP/IPsec, and OpenVPN
- AWS : Autoscaling group (ASG)
- AWS : Setting up Autoscaling Alarms and Notifications via CLI and Cloudformation
- AWS : Adding a SSH User Account on Linux Instance
- AWS : Windows Servers - Remote Desktop Connections using RDP
- AWS : Scheduled stopping and starting an instance - python & cron
- AWS : Detecting stopped instance and sending an alert email using Mandrill smtp
- AWS : Elastic Beanstalk with NodeJS
- AWS : Elastic Beanstalk Inplace/Rolling Blue/Green Deploy
- AWS : Identity and Access Management (IAM) Roles for Amazon EC2
- AWS : Identity and Access Management (IAM) Policies, sts AssumeRole, and delegate access across AWS accounts
- AWS : Identity and Access Management (IAM) sts assume role via aws cli2
- AWS : Creating IAM Roles and associating them with EC2 Instances in CloudFormation
- AWS Identity and Access Management (IAM) Roles, SSO(Single Sign On), SAML(Security Assertion Markup Language), IdP(identity provider), STS(Security Token Service), and ADFS(Active Directory Federation Services)
- AWS : Amazon Route 53
- AWS : Amazon Route 53 - DNS (Domain Name Server) setup
- AWS : Amazon Route 53 - subdomain setup and virtual host on Nginx
- AWS Amazon Route 53 : Private Hosted Zone
- AWS : SNS (Simple Notification Service) example with ELB and CloudWatch
- AWS : Lambda with AWS CloudTrail
- AWS : SQS (Simple Queue Service) with NodeJS and AWS SDK
- AWS : Redshift data warehouse
- AWS : CloudFormation
- AWS : CloudFormation Bootstrap UserData/Metadata
- AWS : CloudFormation - Creating an ASG with rolling update
- AWS : Cloudformation Cross-stack reference
- AWS : OpsWorks
- AWS : Network Load Balancer (NLB) with Autoscaling group (ASG)
- AWS CodeDeploy : Deploy an Application from GitHub
- AWS EC2 Container Service (ECS)
- AWS EC2 Container Service (ECS) II
- AWS Hello World Lambda Function
- AWS Lambda Function Q & A
- AWS Node.js Lambda Function & API Gateway
- AWS API Gateway endpoint invoking Lambda function
- AWS API Gateway invoking Lambda function with Terraform
- AWS API Gateway invoking Lambda function with Terraform - Lambda Container
- Amazon Kinesis Streams
- AWS: Kinesis Data Firehose with Lambda and ElasticSearch
- Amazon DynamoDB
- Amazon DynamoDB with Lambda and CloudWatch
- Loading DynamoDB stream to AWS Elasticsearch service with Lambda
- Amazon ML (Machine Learning)
- Simple Systems Manager (SSM)
- AWS : RDS Connecting to a DB Instance Running the SQL Server Database Engine
- AWS : RDS Importing and Exporting SQL Server Data
- AWS : RDS PostgreSQL & pgAdmin III
- AWS : RDS PostgreSQL 2 - Creating/Deleting a Table
- AWS : MySQL Replication : Master-slave
- AWS : MySQL backup & restore
- AWS RDS : Cross-Region Read Replicas for MySQL and Snapshots for PostgreSQL
- AWS : Restoring Postgres on EC2 instance from S3 backup
- AWS : Q & A
- AWS : Security
- AWS : Security groups vs. network ACLs
- AWS : Scaling-Up
- AWS : Networking
- AWS : Single Sign-on (SSO) with Okta
- AWS : JIT (Just-in-Time) with Okta
Ph.D. / Golden Gate Ave, San Francisco / Seoul National Univ / Carnegie Mellon / UC Berkeley / DevOps / Deep Learning / Visualization
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