Tested and working on 11/15/2023 !

# Create root CA
[acool@localhost tls]$openssl req --x509 --nodes --days 3650 --newkey rsa:2048 --keyout ENT-CA.key --out ENT-CA.crt

# Crate new key and signing request (Tip: remove --aes256 to remove passphrase requirement... I think)
Passphrase: mypassphrase
[acool@localhost tls]$openssl genrsa --out star-dev-localhost.key --aes256 2048
[acool@localhost tls]$openssl req --new --key star-dev-localhost.key --out star-dev-localhost.csr

# Sign request
[acool@localhost tls]$openssl x509 --req --in star-dev-localhost.csr --CA ENT-CA.crt --CAkey ENT-CA.key --CAcreateserial --days 3650 --sha256 --extfile star-dev-localhost.cnf --out star-dev-localhost.crt

# remove passphrase
[acool@localhost tls]$openssl rsa --in star-dev-localhost.key --out star-dev-localhost-nopassphrase.key

[acool@localhost tls]$ cat star-dev-localhost.cnf 
authorityKeyIdentifier = keyid,issuer
basicConstraints = CA:FALSE
keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
subjectAltName = @alt_names

[alt_names]
DNS.1 = *.dev.localhost
[acool@localhost tls]$
[acool@localhost tls]


# finally, import ENT-CA.crt certificate in Chrome
# chrome://settings/certificates

Configure Nginx:

...
listen 443 ssl;
ssl_certificate /etc/ssl/certs/star-dev-localhost.crt;
ssl_certificate_key /etc/ssl/certs/star-dev-localhost-nopassphrase.key;
...

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---

[acool@localhost ~]$ 
[acool@localhost ~]$ date
Mon Apr  3 11:17:50 AM PDT 2023
[acool@localhost ~]$ 
[acool@localhost ~]$ cat c-foreach-macro.c 
#include <stdio.h>

#define foreach(item, array) \
    for(int keep = 1, \
            count = 0,\
            size = sizeof (array) / sizeof *(array); \
        keep && count != size; \
        keep = !keep, count++) \
      for(item = (array) + count; keep; keep = !keep)

int main()
{
    int mynumbers[] = {5,20,35,62,8,74,89};
    
    char mygreeting[] = {"Hello world!"};

    float myfloats[] = {1.6,6.9,5.8,43.5,1.1,0.9};

    foreach(int *v, mynumbers) {
        printf("value: %d\n", *v);
    }

    foreach(char *v, mygreeting) {
        printf("value: %c\n", *v);
    }

    foreach(float *v, myfloats) {
        printf("value: %.2f\n", *v);
    }

    return 0;
}
[acool@localhost ~]$ 
[acool@localhost ~]$ gcc c-foreach-macro.c -o c-foreach-macro
[acool@localhost ~]$ 
[acool@localhost ~]$ ./c-foreach-macro 
value: 5
value: 20
value: 35
value: 62
value: 8
value: 74
value: 89
value: H
value: e
value: l
value: l
value: o
value:  
value: w
value: o
value: r
value: l
value: d
value: !
value: 
value: 1.60
value: 6.90
value: 5.80
value: 43.50
value: 1.10
value: 0.90
[acool@localhost ~]$

Bonus - dumping output from preprocessor.

[acool@localhost ~]$ 
[acool@localhost ~]$ gcc c-foreach-macro.c -E -o c-macro.preprocessed
[acool@localhost ~]$ 
[acool@localhost ~]$ cat c-macro.preprocessed
...
int main()
{
    int mynumbers[] = {5,20,35,62,8,74,89};

    char mygreeting[] = {"Hello world!"};

    float myfloats[] = {1.6,6.9,5.8,43.5,1.1,0.9};

    for(int keep = 1, count = 0, size = sizeof (mynumbers) / sizeof *(mynumbers); keep && count != size; keep = !keep, count++) for(int *v = (mynumbers) + count; keep; keep = !keep) {
        printf("value: %d\n", *v);
    }

    for(int keep = 1, count = 0, size = sizeof (mygreeting) / sizeof *(mygreeting); keep && count != size; keep = !keep, count++) for(char *v = (mygreeting) + count; keep; keep = !keep) {
        printf("value: %c\n", *v);
    }

    for(int keep = 1, count = 0, size = sizeof (myfloats) / sizeof *(myfloats); keep && count != size; keep = !keep, count++) for(float *v = (myfloats) + count; keep; keep = !keep) {
        printf("value: %.2f\n", *v);
    }

    return 0;
}
[acool@localhost ~]$ 

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---

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

void child( int seconds );

int children = 15;

int main(void)
{
  printf("Parent ID %d, Main ID %d \n", getppid(), getpid()); 

  for(int i=0;i<children;i++)
  {
    if(fork()==0)
    {
      child(children-i); // pass seconds to sleep
    }
    else
    {
      wait(NULL);
    }
  }
}

void child(int seconds)
{
  printf("Parent ID %d, Child ID %d, Sleeping %d seconds.\n", getppid(), getpid(), seconds); 
  sleep(seconds);
  exit(0);
}

[acool@localhost C-Exercises]$ date
Sun Oct 23 04:14:24 PM PDT 2022
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ gcc parent_children.c 
[acool@localhost C-Exercises]$ ./a.out 
Parent ID 4298, Main ID 10357 
Parent ID 10357, Child ID 10358, Sleeping 15 seconds.
Parent ID 10357, Child ID 10394, Sleeping 14 seconds.
Parent ID 10357, Child ID 10436, Sleeping 13 seconds.
Parent ID 10357, Child ID 10475, Sleeping 12 seconds.
Parent ID 10357, Child ID 10510, Sleeping 11 seconds.
Parent ID 10357, Child ID 10532, Sleeping 10 seconds.
Parent ID 10357, Child ID 10546, Sleeping 9 seconds.
Parent ID 10357, Child ID 10558, Sleeping 8 seconds.
Parent ID 10357, Child ID 10581, Sleeping 7 seconds.
Parent ID 10357, Child ID 10598, Sleeping 6 seconds.
Parent ID 10357, Child ID 10607, Sleeping 5 seconds.
Parent ID 10357, Child ID 10613, Sleeping 4 seconds.
Parent ID 10357, Child ID 10647, Sleeping 3 seconds.
Parent ID 10357, Child ID 10732, Sleeping 2 seconds.
Parent ID 10357, Child ID 10815, Sleeping 1 seconds.
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ ps -A |grep a.out
  10357 pts/0    00:00:00 a.out
  10394 pts/0    00:00:00 a.out
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ pstree -p 10357
a.out(10357)───a.out(10436)
[acool@localhost C-Exercises]$ 

Slightly different version, in this version we don't wait() for each child individually.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

void child( int seconds );

int children = 15;

int main(void)
{
  printf("Parent ID %d, Main ID %d \n", getppid(), getpid()); 

  for(int i=0;i<children;i++)
  {
    if(fork()==0)
    {
      child(children-i); // pass seconds to sleep
    }
  }

  while (wait(NULL) > 0); // wait for all children to finish
}

void child(int seconds)
{
  printf("Parent ID %d, Child ID %d, Sleeping %d seconds.\n", getppid(), getpid(), seconds); 
  sleep(seconds);
  exit(0);
}

[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ gcc parent_children.c 
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ ./a.out 
Parent ID 4298, Main ID 14322 
Parent ID 14322, Child ID 14323, Sleeping 15 seconds.
Parent ID 14322, Child ID 14324, Sleeping 14 seconds.
Parent ID 14322, Child ID 14325, Sleeping 13 seconds.
Parent ID 14322, Child ID 14326, Sleeping 12 seconds.
Parent ID 14322, Child ID 14327, Sleeping 11 seconds.
Parent ID 14322, Child ID 14328, Sleeping 10 seconds.
Parent ID 14322, Child ID 14329, Sleeping 9 seconds.
Parent ID 14322, Child ID 14330, Sleeping 8 seconds.
Parent ID 14322, Child ID 14331, Sleeping 7 seconds.
Parent ID 14322, Child ID 14332, Sleeping 6 seconds.
Parent ID 14322, Child ID 14333, Sleeping 5 seconds.
Parent ID 14322, Child ID 14334, Sleeping 4 seconds.
Parent ID 14322, Child ID 14335, Sleeping 3 seconds.
Parent ID 14322, Child ID 14336, Sleeping 2 seconds.
Parent ID 14322, Child ID 14337, Sleeping 1 seconds.
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ pstree -p 14322
a.out(14322)─┬─a.out(14323)
             ├─a.out(14324)
             ├─a.out(14325)
             ├─a.out(14326)
             ├─a.out(14327)
             ├─a.out(14328)
             ├─a.out(14329)
             ├─a.out(14330)
             ├─a.out(14331)
             ├─a.out(14332)
             ├─a.out(14333)
             ├─a.out(14334)
             └─a.out(14335)
[acool@localhost C-Exercises]$ ps -A |grep a.out
  14322 pts/0    00:00:00 a.out
  14323 pts/0    00:00:00 a.out
  14324 pts/0    00:00:00 a.out
  14325 pts/0    00:00:00 a.out
  14326 pts/0    00:00:00 a.out
  14327 pts/0    00:00:00 a.out
  14328 pts/0    00:00:00 a.out
  14329 pts/0    00:00:00 a.out
  14330 pts/0    00:00:00 a.out
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ 
[acool@localhost C-Exercises]$ pstree -p 14322
a.out(14322)─┬─a.out(14323)
             ├─a.out(14324)
             ├─a.out(14325)
             ├─a.out(14326)
             ├─a.out(14327)
             └─a.out(14328)
[acool@localhost C-Exercises]$
[acool@localhost C-Exercises]$

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---

#include <stdio.h>
#include <wchar.h>
#include <locale.h>

// multibyte array, each character is 4 bytes long
wchar_t mystring[] = L"Angel Cool á 🤪 😁 ა";

// [acool@localhost other]$ gcc -Wall -ggdb emoji-multibyte-array.c -o emoji-multibyte-array
int main()
{
    setlocale(LC_ALL,"");

    // print total number of characters in string
    wprintf(L"wcslen of wchar_t mystring[]: %ld\n", wcslen(mystring));

    // output string
    wprintf(L"%ls\n",mystring);

    // print one character
    wprintf(L"Emoji : %lc\n", mystring[13]);

    // print all 
    for (int j = 0; j < wcslen(mystring); ++j)
    {
        wprintf(L"%lc,", mystring[j]);
    }

    wprintf(L"\n");

    // size in bytes of string, it also includes 4 bytes for the null (\0) characters at the end it seems 
    wprintf(L"Size in bytes of mystring[]: %d\n", sizeof(mystring));

    // print size of wchar_t data type
    wprintf(L"wchar_t is %d bytes long!\n", sizeof(wchar_t));

    return 0;
}

[acool@localhost other]$ date
Sat Oct 22 12:05:24 PM PDT 2022
[acool@localhost other]$ gcc emoji-multibyte-array.c 
[acool@localhost other]$ ./a.out 
wcslen of wchar_t mystring[]: 18
Angel Cool á 🤪 😁 ა
Emoji : 🤪
A,n,g,e,l, ,C,o,o,l, ,á, ,🤪, ,😁, ,ა,
Size in bytes of mystring[]: 76
wchar_t is 4 bytes long!
[acool@localhost other]$

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---

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main()
{
    pid_t pid;
    int status;

    pid = fork();

    if(pid<0)
    {
        printf("Error: fork() returned %u.\n", pid);
        return 1;
    }

    if(pid == 0)
    {
        printf("Child: PID is %u. Parent's PID is %u\n", getpid(), getppid());
        sleep(10);
        puts("Child: about to exit.\n");
        return 33;
    }
    else
    {
        printf("Parent: PID is %u. Child's PID is %u\n", getpid(), pid);

        while((pid=waitpid(-1,&status,WNOHANG)) == 0)
        {
            printf("Parent: No child has terminated.");
            printf("Parent: Going to sleep for 1 second.\n");
            sleep(1);
        }
    }

    printf("Parent: child with PID %u ", pid);

    if(WIFEXITED(status)!=0)
    {
        printf("exited with status %u\n",WIFEXITED(status));
    }
    else
    {
        printf("exited abnormally\n");
    }

    return 0;
}

Preventing Zombie Processes Using waitpid()
Listing 19.5 -Teach Yourself C For Linux Programming

[acool@localhost C-practice]$ gcc -Wall fork.c
[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ ./a.out 
Parent: PID is 57544. Child's PID is 57545
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Child: PID is 57545. Parent's PID is 57544
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Parent: No child has terminated.Parent: Going to sleep for 1 second.
Child: about to exit.

Parent: child with PID 57545 exited with status 1
[acool@localhost C-practice]$ 
[acool@localhost C-practice]$

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---

Method 1:

// define it as a template
struct person {
 char first_name[50];
 char last_name[50];
};

// create two instances of person
struct person Person1, Person2;

// assign values to Person1
strcpy(Person1.first_name, "Angel");
strcpy(Person1.last_name, "Cool");

Method 2:

// define it and create two instances of it
struct car {
 char make[50];
 char color[50];
} Car1, Car2;

// assign values to Car1
strcpy(Car1.make, "Chevy");
strcpy(Car1.color, "red");

Method 3:

// use 'typedef' to create it
typedef struct {
 char first_name[50];
 char last_name[50];
} person;

// create two instances of person (no 'struct' keyword needed)
person Person1, Person2;

Method 1 example

[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ cat method_1.c 
#include <stdio.h>
#include <string.h>

void main(){
    struct person {
      char first_name[50];
      char last_name[50];
    };

    // create two instances of person
    struct person Person1, Person2;

    // assign values to Person1
    strcpy(Person1.first_name, "Angel");
    strcpy(Person1.last_name, "Cool");
    
    // print assigned values 
    printf("Hello %s %s!\n", Person1.first_name, Person1.last_name);
}
[acool@localhost C-practice]$ gcc method_1.c -o method_1
[acool@localhost C-practice]$ ./method_1 
Hello Angel Cool!
[acool@localhost C-practice]$ 

Method 2 example

[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ cat method_2.c 
#include <stdio.h>
#include <string.h>

void main(){
    // define it and create two instances of it
    struct car {
      char make[50];
      char color[50];
    } Car1, Car2;

    // assign values to Car1
    strcpy(Car1.make, "Chevy");
    strcpy(Car1.color, "red");

    // print assigned values
    printf("My %s %s.\n",Car1.color, Car1.make);
}
[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ gcc method_2.c -o method_2
[acool@localhost C-practice]$ ./method_2
My red Chevy.
[acool@localhost C-practice]$ 

Method 3 example

[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ cat method_3.c 
#include <stdio.h>
#include <string.h>

void main(){
    // use 'typedef' to create it
    typedef struct {
      char first_name[50];
      char last_name[50];
    } person;

    // create two instances of person (no 'struct' keyword needed)
    person Person1, Person2;

    // assign values to Person1
    strcpy(Person1.first_name, "Andres Manuel");
    strcpy(Person1.last_name, "Lopez-Obrador");

    printf("Viva la 4T! Viva %s %s!\n", Person1.first_name, Person1.last_name);
}
[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ gcc method_3.c -o method_3
[acool@localhost C-practice]$ ./method_3
Viva la 4T! Viva Andres Manuel Lopez-Obrador!
[acool@localhost C-practice]$ 
[acool@localhost C-practice]$ 

Another example:

[acool@localhost ~]$ 
[acool@localhost ~]$ 
[acool@localhost ~]$ date
Wed Apr  5 02:18:30 PM PDT 2023
[acool@localhost ~]$ 
[acool@localhost ~]$ cat books.c 
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct Books {
    char title[50];
    char author[50];
    char subject[100];
    int id;
};

typedef struct {
    char title[50];
    char author[50];
    char subject[100];
    int id;
} eBooks;

void printdetails(eBooks *myEbook, struct Books *myBook)
{
  printf( "myBook id : %d\n", myBook->id);
  printf( "myBook title : %s\n", myBook->title);
  printf( "myBook author : %s\n", myBook->author);
  printf( "myBook subject : %s\n", myBook->subject);
  
  printf("====================================\n");

  printf( "myEbook id : %d\n", myEbook->id);
  printf( "myEbook title : %s\n", myEbook->title);
  printf( "myEbook author : %s\n", myEbook->author);
  printf( "myEbook subject : %s\n", myEbook->subject);
}

int main()
{
    // Pay attention to this! ...two different ways to declare it.
   struct Books *myBook = (struct Books *) malloc(sizeof(struct Books));
   eBooks *myEbook = (eBooks *) malloc(sizeof(eBooks));

   strcpy( myBook->title, "C Programming");
   strcpy( myBook->author, "Angel Cool"); 
   strcpy( myBook->subject, "Programming C Structs Examples");
   myBook->id = 1;
 
   strcpy( myEbook->title, "C Programming (eBook)");
   strcpy( myEbook->author, "Angel Cool (eBook)"); 
   strcpy( myEbook->subject, "Programming C Structs Examples (eBook)");
   myEbook->id = 2;
 
   printdetails(myEbook,myBook);

   return 0;
}
[acool@localhost ~]$ 
[acool@localhost ~]$ 
[acool@localhost ~]$ gcc books.c -o books
[acool@localhost ~]$ 
[acool@localhost ~]$ ./books 
myBook id : 1
myBook title : C Programming
myBook author : Angel Cool
myBook subject : Programming C Structs Examples
====================================
myEbook id : 2
myEbook title : C Programming (eBook)
myEbook author : Angel Cool (eBook)
myEbook subject : Programming C Structs Examples (eBook)
[acool@localhost ~]$ 
[acool@localhost ~]$ file books
books: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=ea1090588d4c761da3060066a7d7a67b7db9caa6, for GNU/Linux 3.2.0, not stripped
[acool@localhost ~]$ 
[acool@localhost ~]$

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---

[acool@localhost EC2-VPC]$ 
[acool@localhost EC2-VPC]$ date
Sun Jul  4 06:19:34 PM PDT 2021
[acool@localhost EC2-VPC]$ cat /etc/redhat-release 
Fedora release 33 (Thirty Three)
[acool@localhost EC2-VPC]$ aws --version
aws-cli/1.18.223 Python/3.9.5 Linux/5.12.13-200.fc33.x86_64 botocore/1.19.63
[acool@localhost EC2-VPC]$ terraform -v
Terraform v1.0.1
on linux_amd64
+ provider registry.terraform.io/hashicorp/aws v3.48.0
[acool@localhost EC2-VPC]$

The gist of this post:

 
[acool@localhost EC2-VPC]$ 
[acool@localhost EC2-VPC]$ cat main.tf 
# extract public ssh key from private ssh key
# [acool@localhost EC2-VPC]$ ssh-keygen -y -f ./COOL_SSH_PRIVATEKEY.pem > COOL_SSH_PUBLICKEY.pub 

// a.- set region to use
provider "aws" {
    region = "us-east-2"
}

// b.- create ssh key pair
resource "aws_key_pair" "COOL_KEY_PAIR" {
  key_name   = "COOL_SSH_KEYPAIR"
  public_key = "${file("./COOL_SSH_PUBLICKEY.pub")}"
}

// c.- create vpc resource
resource "aws_vpc" "COOL_VPC" {
    enable_dns_support = true
    enable_dns_hostnames = true
    assign_generated_ipv6_cidr_block = true
    cidr_block = "10.0.0.0/16"
}

// d.- create subnet
resource "aws_subnet" "COOL_VPC_SUBNET" {
    vpc_id = "${aws_vpc.COOL_VPC.id}"
    cidr_block = "${cidrsubnet(aws_vpc.COOL_VPC.cidr_block, 4, 1)}"
    map_public_ip_on_launch = true

    ipv6_cidr_block = "${cidrsubnet(aws_vpc.COOL_VPC.ipv6_cidr_block, 8, 1)}"
    assign_ipv6_address_on_creation = true
}

// e.- create internet gateway
resource "aws_internet_gateway" "COOL_GATEWAY" {
    vpc_id = "${aws_vpc.COOL_VPC.id}"
}

// f.- create routing table
resource "aws_default_route_table" "COOL_VPC_ROUTING_TABLE" {
    default_route_table_id = "${aws_vpc.COOL_VPC.default_route_table_id}"

    route {
        cidr_block = "0.0.0.0/0"
        gateway_id = "${aws_internet_gateway.COOL_GATEWAY.id}"
    }

    route {
        ipv6_cidr_block = "::/0"
        gateway_id = "${aws_internet_gateway.COOL_GATEWAY.id}"
    }
}

// g.- create some sort of association needed
resource "aws_route_table_association" "COOL_SUBNET_ROUTE_TABLE_ASSOCIATION" {
    subnet_id      = "${aws_subnet.COOL_VPC_SUBNET.id}"
    route_table_id = "${aws_default_route_table.COOL_VPC_ROUTING_TABLE.id}"
}

// h.- create security group
resource "aws_security_group" "COOL_SECURITY_GROUP" {
    name = "COOL_SECURITY_GROUP"
    vpc_id = "${aws_vpc.COOL_VPC.id}"
    
    ingress {
        from_port = 22
        to_port = 22
        protocol = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    ingress {
        from_port = 22
        to_port = 22
        protocol = "tcp"
        ipv6_cidr_blocks = ["::/0"]
    }

    // allow ping
    ingress{
        from_port = -1
        to_port = -1
        protocol = "icmp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // allow ping
    ingress{
        from_port = -1
        to_port = -1
        protocol = "icmpv6"
        ipv6_cidr_blocks = ["::/0"]
    }

    egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      cidr_blocks = ["0.0.0.0/0"]
    }

    egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      ipv6_cidr_blocks = ["::/0"]
    }
}

// i.- create EC2 instance
resource "aws_instance" "COOL_INSTANCE_APP01" {
    ami = "ami-01d5ac8f5f8804300"
    key_name = "COOL_SSH_KEYPAIR"
    instance_type = "t2.micro"
    subnet_id = "${aws_subnet.COOL_VPC_SUBNET.id}"
    ipv6_address_count = 1
    vpc_security_group_ids = ["${aws_security_group.COOL_SECURITY_GROUP.id}"]

    tags = {
        Name = "COOL_INSTANCE_APP01"
    }

    depends_on = [aws_internet_gateway.COOL_GATEWAY]
}

//j.- print instance IPs
output "COOL_INSTANCE_APP01_IPv4" {
  value = "${aws_instance.COOL_INSTANCE_APP01.public_ip}"
}

output "COOL_INSTANCE_APP01_IPv6" {
  value = ["${aws_instance.COOL_INSTANCE_APP01.ipv6_addresses}"]
}
[acool@localhost EC2-VPC]$
[acool@localhost EC2-VPC]$ terraform init
...
[acool@localhost EC2-VPC]$ 
[acool@localhost EC2-VPC]$ terraform apply
...
[acool@localhost EC2-VPC]$

Happy 4th of July, 2021! and cheers!


UPDATE - November 9, 2021
Added 'app_servers' variable to create multiple aws_instances.
Commit message: 'Added EIP and specified private ip addresses.'

main.tf :

# extract public ssh key from private ssh key
# [acool@localhost EC2-VPC]$ ssh-keygen -y -f ./COOL_SSH_PRIVATEKEY.pem > COOL_SSH_PUBLICKEY.pub 

// set region to use
provider "aws" {
    region = "us-east-2"
}

// create ssh key pair
resource "aws_key_pair" "COOL_KEY_PAIR" {
  key_name   = "COOL_SSH_KEYPAIR"
  public_key = "${file("./COOL_SSH_PUBLICKEY.pub")}"
}

// create vpc resource
resource "aws_vpc" "COOL_VPC" {
    enable_dns_support = true
    enable_dns_hostnames = true
    assign_generated_ipv6_cidr_block = true
    cidr_block = "10.0.0.0/16"
}

// create subnet
resource "aws_subnet" "COOL_PVC_SUBNET" {
    vpc_id = "${aws_vpc.COOL_VPC.id}"
    cidr_block = "${cidrsubnet(aws_vpc.COOL_VPC.cidr_block, 4, 1)}"
    map_public_ip_on_launch = true

    ipv6_cidr_block = "${cidrsubnet(aws_vpc.COOL_VPC.ipv6_cidr_block, 8, 1)}"
    assign_ipv6_address_on_creation = true
}

// create internet gateway
resource "aws_internet_gateway" "COOL_GATEWAY" {
    vpc_id = "${aws_vpc.COOL_VPC.id}"
}

// create routing table
resource "aws_default_route_table" "COOL_VPC_ROUTING_TABLE" {
    default_route_table_id = "${aws_vpc.COOL_VPC.default_route_table_id}"

    route {
        cidr_block = "0.0.0.0/0"
        gateway_id = "${aws_internet_gateway.COOL_GATEWAY.id}"
    }

    route {
        ipv6_cidr_block = "::/0"
        gateway_id = "${aws_internet_gateway.COOL_GATEWAY.id}"
    }
}

// create some sort of association needed
resource "aws_route_table_association" "COOL_SUBNET_ROUTE_TABLE_ASSOCIATION" {
    subnet_id      = "${aws_subnet.COOL_PVC_SUBNET.id}"
    route_table_id = "${aws_default_route_table.COOL_VPC_ROUTING_TABLE.id}"
}

// create security group
resource "aws_security_group" "COOL_SECURITY_GROUP" {
    name = "COOL_SECURITY_GROUP"
    vpc_id = "${aws_vpc.COOL_VPC.id}"
    
    ingress {
        from_port = 22
        to_port = 22
        protocol = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    ingress {
        from_port = 22
        to_port = 22
        protocol = "tcp"
        ipv6_cidr_blocks = ["::/0"]
    }

    // allow ping
    ingress{
        from_port = -1
        to_port = -1
        protocol = "icmp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // allow ping
    ingress{
        from_port = -1
        to_port = -1
        protocol = "icmpv6"
        ipv6_cidr_blocks = ["::/0"]
    }

    egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      cidr_blocks = ["0.0.0.0/0"]
    }

    egress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      ipv6_cidr_blocks = ["::/0"]
    }
}

// server names
variable app_servers {
    description = "name of app servers"
    type = list(map(any))
    default = [
        {name:"COOL_LB01", ip:"10.0.16.4"},
        {name:"COOL_LB02", ip:"10.0.16.5"},
        {name:"COOL_APP01", ip:"10.0.16.6"},
        {name:"COOL_APP02", ip:"10.0.16.7"},
    ]
}

// create EC2 instance
resource "aws_instance" "COOL_SERVERS" {
    ami = "ami-01d5ac8f5f8804300"
    key_name = "COOL_SSH_KEYPAIR"
    instance_type = "t2.micro"
    subnet_id = "${aws_subnet.COOL_PVC_SUBNET.id}"
    ipv6_address_count = 1
    vpc_security_group_ids = ["${aws_security_group.COOL_SECURITY_GROUP.id}"]
    for_each = {for server in var.app_servers:  server.name => server}
    private_ip = each.value["ip"]

    tags = {
        Name = each.value["name"]
    }

    depends_on = [aws_internet_gateway.COOL_GATEWAY]
}

// elastic IP
resource "aws_eip" "COOL_EIP" {
  instance = aws_instance.COOL_SERVERS["COOL_LB01"].id
  vpc      = true
}

// print instance IPs
output "COOL_INSTANCE_APP01_IPv4" {
    value = {for k, v in aws_instance.COOL_SERVERS: k => v.public_ip}
}

output "COOL_INSTANCE_APP01_IPv6" {
  value = {for k, v in aws_instance.COOL_SERVERS: k => v.ipv6_addresses}
}

output "COOL_VPC_IPV6_BLOCK" {
  value = aws_subnet.COOL_PVC_SUBNET.ipv6_cidr_block
}

// SSH to instance:
// [acool@localhost EC2-VPC]$ ssh -i ./COOL_SSH_PRIVATEKEY.pem centos@ip_address

// remove eip from COOL_LB01
// [acool@localhost EC2-VPC]$ aws ec2 disassociate-address --region us-east-2 --public-ip 3.131.249.150

// assign eip to COOL_LB02, adjust instance id to match LB02. The same commands work to return eip to LB01
// [acool@localhost EC2-VPC]$ aws ec2 associate-address --region us-east-2 --public-ip 3.131.249.150 --instance-id i-05a634252654b7b34

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---

[acool@localhost terraform-tests]$ terraform --version
Terraform v1.0.1
...
[acool@localhost terraform-tests]$ aws --version
aws-cli/1.18.223 Python/3.9.5 Linux/5.12.12-200.fc33.x86_64 botocore/1.19.63
...

The gist of this post:

[acool@localhost EC2-SINGLE-INSTANCE]$ cat main.tf 
provider "aws" {
    region = "us-east-2"
}

// create ssh key
resource "tls_private_key" "COOL_SSH_PK" {
  algorithm = "RSA"
  rsa_bits  = 4096
}

// create ssh key pair
resource "aws_key_pair" "COOL_KEY_PAIR" {
  key_name   = "COOL_SSH_KEYNAME"
  public_key = tls_private_key.COOL_SSH_PK.public_key_openssh

  provisioner "local-exec" { # Create "myKey.pem" to your computer!!
    command = "echo '${tls_private_key.COOL_SSH_PK.private_key_pem}' > ./COOL_SSH_PK.pem"
  }
}

// create aws ec2 instance
resource "aws_instance" "COOLAPP01" {
    ami = "ami-01d5ac8f5f8804300"
    instance_type = "t2.micro"
    key_name = aws_key_pair.COOL_KEY_PAIR.key_name
    vpc_security_group_ids = [aws_security_group.COOLAPP01_security_group.id]

  tags = {
    Name = "COOLAPP01_tag_name"
  }
}

// create security group
resource "aws_security_group" "COOLAPP01_security_group" {

    name="terraform_COOLAPP01_security_group"

    // allow port 80 tcp
    ingress{
        from_port = 80
        to_port = 80
        protocol = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // allow port 22 tcp
    ingress{
        from_port = 22
        to_port = 22
        protocol = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // allow ping
    ingress{
        from_port = -1
        to_port = -1
        protocol = "icmp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // allow all outbound traffic
    egress {
        from_port   = 0
        to_port     = 0
        protocol    = "-1"
        cidr_blocks = ["0.0.0.0/0"]
    }
}

// TODO: enable IPV6

output "public_ip" {
    value = aws_instance.COOLAPP01.public_ip
    description = "public ip for COOLAPP01"
}
[acool@localhost EC2-SINGLE-INSTANCE]$ 
[acool@localhost EC2-SINGLE-INSTANCE]$terraform apply
...

Happy 4th of July, 2021 ya'll!!

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---

We're gonna use Keepalived's VRRP feature.

Floating ip address will be 192.168.121.179

Vagrantfile needed parameters:

config.vm.box = "centos/8"
config.vm.network "private_network", ip: "192.168.121.180"
config.vm.hostname = "lb01.localhost"

config.vm.box = "centos/8"
config.vm.network "private_network", ip: "192.168.121.181"
config.vm.hostname = "lb02.localhost"

config.vm.box = "centos/8"
config.vm.network "private_network", ip: "192.168.121.191"
config.vm.hostname = "app01.localhost"

config.vm.box = "centos/8"
config.vm.network "private_network", ip: "192.168.121.192"
config.vm.hostname = "app02.localhost"

------------------------------------------------------------------------
app01 and app02 will have nginx installed running its default welcome page.

angel@acool:~/Documents/haproxy-cluster$ date
Fri 21 May 2021 07:11:52 PM PDT
angel@acool:~/Documents/haproxy-cluster$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04.2 LTS"
angel@acool:~/Documents/haproxy-cluster$ 
angel@acool:~/Documents/haproxy-cluster$ tree
.
├── app01
│   └── Vagrantfile
├── app02
│   └── Vagrantfile
├── lb01
│   └── Vagrantfile
├── lb02
│   └── Vagrantfile
└── NOTES.txt

4 directories, 5 files
angel@acool:~/Documents/haproxy-cluster$
angel@acool:~/Documents/haproxy-cluster$ sudo vagrant global-status
id       name    provider state   directory                                   
------------------------------------------------------------------------------
1553a24  default libvirt shutoff /home/angel/Documents/haproxy-cluster/lb01  
3c33424  default libvirt shutoff /home/angel/Documents/haproxy-cluster/lb02  
1d9af06  default libvirt shutoff /home/angel/Documents/haproxy-cluster/app01 
5bc8220  default libvirt shutoff /home/angel/Documents/haproxy-cluster/app02 
...
angel@acool:~/Documents/haproxy-cluster$
angel@acool:~/Documents/haproxy-cluster$
angel@acool:~/Documents/haproxy-cluster/lb01$ vagrant --version
Vagrant 2.2.6
angel@acool:~/Documents/haproxy-cluster$
angel@acool:~/Documents/haproxy-cluster$ cd lb01/
angel@acool:~/Documents/haproxy-cluster/lb01$ sudo vagrant up
...
angel@acool:~/Documents/haproxy-cluster/lb01$ sudo vagrant ssh
Last login: Sat May 22 02:08:45 2021 from 192.168.121.1
[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ cat /etc/redhat-release 
CentOS Linux release 8.3.2011
[vagrant@lb01 ~]$ sudo dnf install haproxy keepalived

[vagrant@lb01 ~]$ haproxy -v
HA-Proxy version 1.8.23 2019/11/25
Copyright 2000-2019 Willy Tarreau <willy@haproxy.org>

[vagrant@lb01 ~]$ keepalived --version
Keepalived v2.0.10 (11/12,2018)
...
[vagrant@lb01 ~]$
[vagrant@lb01 ~]$ # HAProxy need this to bind to floating ip when ip is missing locally 
[vagrant@lb01 ~]$ cat /etc/sysctl.conf 
...
net.ipv4.ip_nonlocal_bind=1
[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ sudo sysctl -p
net.ipv4.ip_nonlocal_bind = 1
[vagrant@lb01 ~]$
[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ cat /etc/haproxy/haproxy.cfg 
...
## enable stats
listen stats
    bind :9000
    stats enable
    stats uri /stats
    stats refresh 10s
    stats admin if LOCALHOST

## enable www frontend, bind floating ip address
frontend www
    bind 192.168.121.179:80
    mode http
    default_backend www_servers

## enable www backend
backend www_servers
    balance roundrobin
    option forwardfor
    http-request set-header X-Forwarded-Port %[dst_port]
    http-request add-header X-Forwarded-Proto https if { ssl_fc }
    option httpchk HEAD / HTTP/1.1\r\nHost:localhost
    server app01 192.168.121.191:80 check
    server app02 192.168.121.192:80 check

[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ cat /etc/keepalived/keepalived.conf
     vrrp_script chk_haproxy {      # Requires keepalived-1.1.13
       #script "killall -0 haproxy"  # cheaper than pidof
       script "pidof haproxy"  # this one worked better for me.
       interval 2 # check every 2 seconds
       weight 2 # add 2 points of priority if OK
     }
     vrrp_instance VI_1 {
       interface eth0
       state MASTER
       virtual_router_id 51
       priority 101 # 101 on lb01, 100 on lb02
       virtual_ipaddress {
         192.168.121.179
       }
       track_script {
         chk_haproxy
       }
     }
[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ # this should be the end result, the floating ip should be listed.
[vagrant@lb01 ~]$ ip a |grep 179
    inet 192.168.121.179/32 scope global eth0
[vagrant@lb01 ~]$ 
[vagrant@lb01 ~]$ # if you stop haproxy (or shutdown lb01), lb02 should take over the floating ip!
[vagrant@lb01 ~]$ # when haproxy is back, lb01 will reclaim the floating ip, the end result is
[vagrant@lb01 ~]$ # the floating ip will be available even if lb01 goes down.

Cheers!

UPDATE: November 11, 2021 - Adding lb02 details in order to remove ambiguities when I see this post in the future.

[vagrant@lb02 ~]$ cat /etc/sysctl.conf 
...
net.ipv4.ip_nonlocal_bind=1
[vagrant@lb02 ~]$

[vagrant@lb02 ~]$ 
[vagrant@lb02 ~]$ 
[vagrant@lb02 ~]$ cat /etc/keepalived/keepalived.conf
     vrrp_script chk_haproxy {      # Requires keepalived-1.1.13
       #script "killall -0 haproxy"  # cheaper than pidof
       script "pidof haproxy"
       interval 2 # check every 2 seconds
       weight 2 # add 2 points of priority if OK
     }
     vrrp_instance VI_1 {
       interface eth0
       state MASTER
       virtual_router_id 51
       priority 100 # 101 on primary, 100 on secondary
       virtual_ipaddress {
         192.168.121.179
       }
       track_script {
         chk_haproxy
       }
     }

[vagrant@lb02 ~]$

[vagrant@lb02 ~]$ 
[vagrant@lb02 ~]$ 
[vagrant@lb02 ~]$ cat /etc/haproxy/haproxy.cfg
#---------------------------------------------------------------------
# Example configuration for a possible web application.  See the
# full configuration options online.
#
#   https://www.haproxy.org/download/1.8/doc/configuration.txt
#
#---------------------------------------------------------------------

#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
    # to have these messages end up in /var/log/haproxy.log you will
    # need to:
    #
    # 1) configure syslog to accept network log events.  This is done
    #    by adding the '-r' option to the SYSLOGD_OPTIONS in
    #    /etc/sysconfig/syslog
    #
    # 2) configure local2 events to go to the /var/log/haproxy.log
    #   file. A line like the following can be added to
    #   /etc/sysconfig/syslog
    #
    #    local2.*                       /var/log/haproxy.log
    #
    log         127.0.0.1 local2

    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon

    # turn on stats unix socket
    stats socket /var/lib/haproxy/stats

    # utilize system-wide crypto-policies
    ssl-default-bind-ciphers PROFILE=SYSTEM
    ssl-default-server-ciphers PROFILE=SYSTEM

#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaults
    mode                    http
    log                     global
    option                  httplog
    option                  dontlognull
    option http-server-close
    option forwardfor       except 127.0.0.0/8
    option                  redispatch
    retries                 3
    timeout http-request    10s
    timeout queue           1m
    timeout connect         10s
    timeout client          1m
    timeout server          1m
    timeout http-keep-alive 10s
    timeout check           10s
    maxconn                 3000

# ME: enable stats
listen stats
    bind :9000
    stats enable
    stats uri /stats
    stats refresh 10s
    stats admin if LOCALHOST

# ME: 
frontend www
    bind 192.168.121.179:80
    mode http
    default_backend www_servers

# ME:
backend www_servers
    balance roundrobin
    option forwardfor
    http-request set-header X-Forwarded-Port %[dst_port]
    http-request add-header X-Forwarded-Proto https if { ssl_fc }
    option httpchk HEAD / HTTP/1.1\r\nHost:localhost
    server app01 192.168.121.191:80 check
    server app02 192.168.121.192:80 check

#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
frontend main
    bind *:5000
    acl url_static       path_beg       -i /static /images /javascript /stylesheets
    acl url_static       path_end       -i .jpg .gif .png .css .js

    use_backend static          if url_static
    default_backend             app

#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
backend static
    balance     roundrobin
    server      static 127.0.0.1:4331 check

#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
backend app
    balance     roundrobin
    server  app1 127.0.0.1:5001 check
    server  app2 127.0.0.1:5002 check
    server  app3 127.0.0.1:5003 check
    server  app4 127.0.0.1:5004 check
[vagrant@lb02 ~]$ 
[vagrant@lb02 ~]$ 

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---

[vagrant@box1 ~]$ date
Fri Dec 11 18:34:51 UTC 2020
[vagrant@box1 ~]$
[vagrant@box1 ~]$ docker --version
Docker version 20.10.0, build 7287ab3
[vagrant@box1 ~]$
[vagrant@box1 ~]$
[vagrant@box1 ~]$  ########## Docker SWARM info ##########
[vagrant@box1 ~]$ docker swarm

Usage:  docker swarm COMMAND

Manage Swarm

Commands:
  ca          Display and rotate the root CA
  init        Initialize a swarm
  join        Join a swarm as a node and/or manager
  join-token  Manage join tokens
  leave       Leave the swarm
  unlock      Unlock swarm
  unlock-key  Manage the unlock key
  update      Update the swarm

Run 'docker swarm COMMAND --help' for more information on a command.
[vagrant@box1 ~]$
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$  ########## Docker NODE info ##########
[vagrant@box1 ~]$ docker node

Usage:  docker node COMMAND

Manage Swarm nodes

Commands:
  demote      Demote one or more nodes from manager in the swarm
  inspect     Display detailed information on one or more nodes
  ls          List nodes in the swarm
  promote     Promote one or more nodes to manager in the swarm
  ps          List tasks running on one or more nodes, defaults to current node
  rm          Remove one or more nodes from the swarm
  update      Update a node

Run 'docker node COMMAND --help' for more information on a command.
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$
[vagrant@box1 ~]$  ########## Docker SERVICE info ##########
[vagrant@box1 ~]$ docker service

Usage:  docker service COMMAND

Manage services

Commands:
  create      Create a new service
  inspect     Display detailed information on one or more services
  logs        Fetch the logs of a service or task
  ls          List services
  ps          List the tasks of one or more services
  rm          Remove one or more services
  rollback    Revert changes to a service's configuration
  scale       Scale one or multiple replicated services
  update      Update a service

Run 'docker service COMMAND --help' for more information on a command.
[vagrant@box1 ~]$
[vagrant@box1 ~]$
[vagrant@box1 ~]$  ########## Docker STACK info ##########
[vagrant@box1 ~]$ docker stack

Usage:  docker stack [OPTIONS] COMMAND

Manage Docker stacks

Options:
      --orchestrator string   Orchestrator to use (swarm|kubernetes|all)

Commands:
  deploy      Deploy a new stack or update an existing stack
  ls          List stacks
  ps          List the tasks in the stack
  rm          Remove one or more stacks
  services    List the services in the stack

Run 'docker stack COMMAND --help' for more information on a command.
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$  ########## Docker NETWORK info ##########
vagrant@box1 ~]$ docker network

Usage:  docker network COMMAND

Manage networks

Commands:
  connect     Connect a container to a network
  create      Create a network
  disconnect  Disconnect a container from a network
  inspect     Display detailed information on one or more networks
  ls          List networks
  prune       Remove all unused networks
  rm          Remove one or more networks

Run 'docker network COMMAND --help' for more information on a command.
[vagrant@box1 ~]$
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$  ########## All the crap available under Docker binary ##########
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$ docker

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default "/home/vagrant/.docker")
  -c, --context string     Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set with "docker
                           context use")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default "/home/vagrant/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/home/vagrant/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/home/vagrant/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  app*        Docker App (Docker Inc., v0.9.1-beta3)
  builder     Manage builds
  buildx*     Build with BuildKit (Docker Inc., v0.4.2-docker)
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts
  image       Manage images
  manifest    Manage Docker image manifests and manifest lists
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.
To get more help with docker, check out guides at https://docs.docker.com/go/guides/
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$ 
[vagrant@box1 ~]$ 

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