install docker-engine issue

sudo apt install docker-engine

Reading package lists... Done

Building dependency tree       

Reading state information... Done

Some packages could not be installed. This may mean that you have

requested an impossible situation or if you are using the unstable

distribution that some required packages have not yet been created

or been moved out of Incoming.

The following information may help to resolve the situation:

The following packages have unmet dependencies:

 docker-engine : Depends: libsystemd-journal0 (>= 201) but it is not installable

                 Recommends: aufs-tools but it is not going to be installed

E: Unable to correct problems, you have held broken packages.

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The program 'docker' is currently not installed.

docker -v

The program 'docker' is currently not installed. You can install it by typing:

sudo apt install docker.io

(my_env) ubuntu@ip-192-31-19-128:/tmp$ sudo apt install docker.io

Reading package lists... Done

Building dependency tree       

Reading state information... Done

The following additional packages will be installed:

  bridge-utils cgroupfs-mount containerd runc ubuntu-fan

Suggested packages:

  mountall aufs-tools debootstrap docker-doc rinse zfs-fuse | zfsutils

The following NEW packages will be installed:

  bridge-utils cgroupfs-mount containerd docker.io runc ubuntu-fan

0 upgraded, 6 newly installed, 0 to remove and 22 not upgraded.

Need to get 16.4 MB of archives.

After this operation, 83.6 MB of additional disk space will be used.

Do you want to continue? [Y/n] Y

Get:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/main amd64 bridge-utils amd64 1.5-9ubuntu1 [28.6 kB]

Get:2 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial/universe amd64 cgroupfs-mount all 1.2 [4970 B]

Get:3 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 runc amd64 1.0.0~rc2+docker1.12.6-0ubuntu1~16.04.1 [1479 kB]

Get:4 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 containerd amd64 0.2.5-0ubuntu1~16.04.1 [4041 kB]

Get:5 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 docker.io amd64 1.12.6-0ubuntu1~16.04.1 [10.8 MB]

Get:6 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu xenial-updates/main amd64 ubuntu-fan all 0.9.2 [30.7 kB]

Fetched 16.4 MB in 1s (12.2 MB/s)

perl: warning: Setting locale failed.

perl: warning: Please check that your locale settings:

LANGUAGE = (unset),

LC_ALL = (unset),

LC_CTYPE = "UTF-8",

LANG = "en_US.UTF-8"

    are supported and installed on your system.

perl: warning: Falling back to a fallback locale ("en_US.UTF-8").

locale: Cannot set LC_CTYPE to default locale: No such file or directory

locale: Cannot set LC_ALL to default locale: No such file or directory

Selecting previously unselected package bridge-utils.

(Reading database ... 62405 files and directories currently installed.)

Preparing to unpack .../bridge-utils_1.5-9ubuntu1_amd64.deb ...

Unpacking bridge-utils (1.5-9ubuntu1) ...

Selecting previously unselected package cgroupfs-mount.

Preparing to unpack .../cgroupfs-mount_1.2_all.deb ...

Unpacking cgroupfs-mount (1.2) ...

Selecting previously unselected package runc.

Preparing to unpack .../runc_1.0.0~rc2+docker1.12.6-0ubuntu1~16.04.1_amd64.deb ...

Unpacking runc (1.0.0~rc2+docker1.12.6-0ubuntu1~16.04.1) ...

Selecting previously unselected package containerd.

Preparing to unpack .../containerd_0.2.5-0ubuntu1~16.04.1_amd64.deb ...

Unpacking containerd (0.2.5-0ubuntu1~16.04.1) ...

Selecting previously unselected package docker.io.

Preparing to unpack .../docker.io_1.12.6-0ubuntu1~16.04.1_amd64.deb ...

Unpacking docker.io (1.12.6-0ubuntu1~16.04.1) ...

Selecting previously unselected package ubuntu-fan.

Preparing to unpack .../ubuntu-fan_0.9.2_all.deb ...

Unpacking ubuntu-fan (0.9.2) ...

Processing triggers for man-db (2.7.5-1) ...

Processing triggers for ureadahead (0.100.0-19) ...

Processing triggers for systemd (229-4ubuntu19) ...

Setting up bridge-utils (1.5-9ubuntu1) ...

locale: Cannot set LC_CTYPE to default locale: No such file or directory

locale: Cannot set LC_ALL to default locale: No such file or directory

Setting up cgroupfs-mount (1.2) ...

Setting up runc (1.0.0~rc2+docker1.12.6-0ubuntu1~16.04.1) ...

Setting up containerd (0.2.5-0ubuntu1~16.04.1) ...

Setting up docker.io (1.12.6-0ubuntu1~16.04.1) ...

Adding group `docker' (GID 116) ...

Done.

Setting up ubuntu-fan (0.9.2) ...

Processing triggers for systemd (229-4ubuntu19) ...

Processing triggers for ureadahead (0.100.0-19) ...

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conda install traitlets tornado jinja2 sqlalchemy 

conda: command not found

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Permission error- Unable to ssh into Amazon EC2 instance

ssh -i ec2-instance-cert.pem root@publicip or public dns

@@@@@@@@@@@@@@@@@@@@@@@@######@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ ###        WARNING: UNPROTECTED PRIVATE KEY FILE! ###   @
@@@@@@@@@@@@@@@@@@@@@@@@######@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Permissions 0644 for 'test.pem' are too open.

It is required that your private key files are NOT accessible by others.

Solution :
key must not be publicly viewable for SSH to work. Use this command if required

$ chmod 400 ec2-instance-cert.pem

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Mongoose

It is an object modeling tool for nodejs that connects MongoDB.Mongoose take the models and maps them to MongoDB database.

install required dependencies
npm install mongoose

var mongoose = require('mongoose');



/*without callback */
mongoose.connect('localhost','mydatabase');

/* with callback */ create a connection object and bind two callabcks.

var db = mongoose.connection;
db.on('open',function callback(){
//connection success
});
db.on('error',function(msg){
//connection error
});

Schema Creation :

var empSchema = mongoose.Schema({
name: String,
designation : String,
location: String,
Skills: String
});

Model Creation :

var Employee =  mongoose.model('employee',empSchema);

Saving the model :

employee.save(function(err,emp){
if(err){
//error handling
}else{
//success
}
});

Reading the model :

var Employee =  mongoose.model('employee',empSchema);

Employee.find(function(err,emp){
if(err){
//error handling
}else{
//success
}
});

Reading specific model :


Employee.find({name:'SrinivasNidadavolu'},function(err,emp){
if(err){
//error handling
}else{
//success
}
});

output:

[{name:'SrinivasNidadavolu',designation:'software engineer',location:'building number 14,Raheja Mindpsace, Hyderabad',Skills:'Java,C++,AWS,AZURE,Containers,cloud specialist'}]

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Elastic Load Balancing

Elastic Load Balancing automatically distributes the incoming application traffic across multiple was ec2 instances.

Two types of load balancers :
Application Load Balancer
Classic Load Balancer

Elastic Load Balancing :
It is in-region load balancing service and distributed traffic  across multiple availability zones -HTTP/S, TCP/S.
Fully fault tolerant
Buit in health check

Application Load Balancer Features:
• It has Containerized Application Support
• It has Content-Based Routing
• It support for  HTTP/2
• Contains Delete Protection
• Supports WebSockets
• Supports Layer-7 Load Balancing
• Supports Web Application Firewall (WAF)
• Contains Request Tracing

Classic Load Balancer Features:
• Contains Health Checks
• It has High Availability
• Supports Security Features
• Supports Sticky Sessions
• Supports SSL Offloading
• Support for Layer 4 or 7 Load Balancing
• It has Operational Monitoring
• provides Logging
• provides IPv6 Support

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Creating Database MongoDB

MongoDB is document based database.
Creating Database NodeJS - MongoDB

Once mongoDB is up and running,

var mongoDB =  require('mongodb');


var mydbserver =  new mongodb.server('localhost', 27017, {auto_reconnect:true});

/* new mongodb.Db() creates a new database */
/* w:1 sets the write concern */

var database =  new mongodb.Db('eCommerceDb',mydbserver, {w:1});



Collections :

Relational databases uses tables to store data. MongoDB stores data as document format uses collection. It is NoSql type database.

Collections are represented as JSON format.

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