Linux : Difference between >> and >

 > redirects output to a file, overwriting the file.

>> redirects output to a file appending the redirected output at the end

https://unix.stackexchange.com/questions/89386/what-is-symbol-and-in-unix-linux

FSTAB Format

https://www.thegeekdiary.com/understanding-the-configuration-file-for-mounting-file-systems-etc-fstab/

https://askubuntu.com/questions/9939/what-do-the-last-two-fields-in-fstab-mean

chmod octet 777 vs -R ugo+rwx ??? Difference

 chmod -R 777 /efs  is not safer

chmod -R ugo+rwx /efs is safer - Does not override SETUID AND SETGID BITS - Just Appends permissions

https://unix.stackexchange.com/questions/296675/is-chmod-r-ugorwx-safer-than-chmod-r-777

sudo tee -a

Append text when using sudo

echo '104.20.186.5 www.cyberciti.biz' | sudo tee -a /etc/hosts

Persist firewal changes iptables redhat 7 across restart ?

Persist iptables redhat 7 ?

https://access.redhat.com/webassets/avalon/d/Red_Hat_Enterprise_Linux-7-Security_Guide-en-US/images/eee9192950e07b21f5c95b3ced63ae09/RHEL_Security-Guide_453350_0717_ECE_firewalld-comparison-rhel7.png

https://www.thegeekdiary.com/centos-rhel-how-to-make-iptable-rules-persist-across-reboots/

[IMPORTANT]

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/security_guide/sec-using_firewalls#sec-Getting_started_with_firewalld

https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units

https://serverfault.com/questions/708728/iptables-not-starting-upon-reboot

https://www.tecmint.com/linux-firewall-iptables-interview-questions-and-answers/    [IMP]

https://www.digitalocean.com/community/tutorials/how-to-configure-a-linux-service-to-start-automatically-after-a-crash-or-reboot-part-1-practical-examples

https://linuxconfig.org/how-to-change-a-runlevel-on-rhel-7-linux-system

Typically the location of iptables configuration lies at ‘/etc/sysconfig/iptables‘ whereas firewalld configuration lies at ‘/etc/firewalld/‘, which is a set of XML files.

EDIT

/etc/firewalld/zones/public.xml

sudo systemctl status firewalld

sudo /sbin/service iptables status

sudo /sbin/service iptables save

sudo less /etc/sysconfig/iptables

sudo iptables -S

sudo iptables -A IN_public_allow -p tcp -m tcp --dport 27017 -m conntrack --ctstate NEW,UNTRACKED -j ACCEPT

-A IN_public_allow -p tcp -m tcp --dport 22 -m conntrack --ctstate NEW,UNTRACKED -j ACCEPT

-A IN_public_allow -p tcp -m tcp --dport 8080 -m conntrack --ctstate NEW,UNTRACKED -j ACCEPT

  <service name="ssh"/>

  <service name="dhcpv6-client"/>

  <port protocol="tcp" port="8080"/>

Redhat :RPM-Build/Make : How to make RPM File from Git Source Code : Make and RPM-Build [ make rpm]

https://docs.aws.amazon.com/efs/latest/ug/installing-amazon-efs-utils.html#installing-other-distro

sudo yum list installed |grep amazon-efs-utils

sudo yum -y install git
sudo yum -y install make
sudo yum -y install rpm-build

git clone https://github.com/aws/efs-utils
cd /path/efs-utils
sudo make rpm
sudo yum -y install ./build/amazon-efs-utils*rpm

AWS Configure : .aws : credentials : config :role_Arn : source_profile: credential_source

https://docs.aws.amazon.com/cli/latest/topic/config-vars.html#the-shared-credentials-file

%UserProfile%/.aws                 [Windows]

~/.aws                                     [Linux]

All these defaults can be changed too

aws configure       [Command to add Secret Key/Access Key using command Line itself]

role_arn and either a source_profile or a credential_source.

• Shared Credentials File
• AWS CLI Conflig File

They both contain Access_Key and Secret_Key

"CLI Config File" - access/Secret Keys are specific to that role
while

The shared credentials file has a default location of ~/.aws/credentials. 

You can change the location of the shared credentials file by setting the AWS_SHARED_CREDENTIALS_FILE environment variable.

The AWS CLI config file, which defaults to ~/.aws/config has the following format:

[default]

aws_access_key_id=foo

aws_secret_access_key=bar

region=us-west-2

Profiles that aren't the default profile are specified by creating a section titled "profile profilename":

[profile testing]

aws_access_key_id=foo

aws_secret_access_key=bar

region=us-west-2

aws_access_key_id, aws_secret_access_key, aws_session_token. These are the only supported values in the shared credential file. Also note that the section names are different than the AWS CLI config file (~/.aws/config). In the AWS CLI config file, you create a new profile by creating a section of [profile profile-name], for example:

[profile development]

aws_access_key_id=foo

aws_secret_access_key=bar

In the shared credentials file, profiles are not prefixed with profile, for example:

[development]

aws_access_key_id=foo

aws_secret_access_key=bar

Credentials specified in the shared credentials file have precedence over credentials in the AWS CLI config file

Shared Credentials File > Config File

Precedence

The above configuration values have the following precedence:

• Command line options
• Environment variables
• Configuration file

Credentials can be specified in several ways:

• Environment variables
• The AWS Shared Credential File
• The AWS CLI config file

AWS : EFS : Mount Target and Mount in EC2

sudo apt-get -y install nfs-common
sudo yum -y install nfs-utils
sudo service nfs start
sudo service nfs status

sudo su -
sudo mkdir -p /efs
sudo chmod -R ugo+rwx /efs     
ls -ld /efs 

echo 'fs-face524e.efs.us-east-1.amazonaws.com:/ /efs nfs4 rw,intr,hard,_netdev,nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport 0 0' >> /etc/fstab

sudo mount -a

sudo reboot now

umount -f efs
sudo mount -a

#fs-face524e.efs.us-east-1.amazonaws.com:/ /efs nfs4 rw,intr,hard,_netdev,nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport 0 0

#echo 'fs-face524e.efs.us-east-1.amazonaws.com:/ /efs nfs4 rw,intr,hard,_netdev,nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport 0 0' | sudo tee -a /etc/fstab

#sudo vi /etc/fstab

chmod -R 777 /efs  is not safer

chmod -R ugo+rwx /efs is safer - Does not override SETUID AND SETGID BITS - Just Appends permissions

https://unix.stackexchange.com/questions/296675/is-chmod-r-ugorwx-safer-than-chmod-r-777

https://www.thegeekdiary.com/understanding-the-configuration-file-for-mounting-file-systems-etc-fstab/

https://askubuntu.com/questions/9939/what-do-the-last-two-fields-in-fstab-mean

The EFS mount helper is part of the amazon-efs-utils package. 

The amazon-efs-utils package is an open-source collection of Amazon EFS tools. 

For more information, see Manually installing the Amazon EFS client.

https://docs.aws.amazon.com/efs/latest/ug/installing-amazon-efs-utils.html#installing-efs-utils-amzn-linux

https://docs.aws.amazon.com/efs/latest/ug/installing-amazon-efs-utils.html#installing-other-distro

Before the Amazon EFS mount helper was available, 

we recommended mounting your Amazon EFS file systems using the standard Linux NFS client.

https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-old.html#mounting-fs-install-nfsclient

https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-mount-cmd-dns-name.html

https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-mount-cmd-ip-addr.html

https://docs.aws.amazon.com/efs/latest/ug/efs-mount-helper.html#mount-fs-auto-mount-onreboot

To view and copy the exact commands to mount your EFS file system using the mount target IP address

Open the Amazon Elastic File System console at https://console.aws.amazon.com/efs/.

In the Amazon EFS console, choose the file system that you want to mount to display its details page.

To display the mount commands to use for this file system, choose Attach in the upper right.

The Attach screen displays the exact commands to use for mounting the file system.

https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_switch-role-ec2_instance-profiles.html

https://kichik.com/2020/09/08/how-does-ec2-instance-profile-work/

https://computingforgeeks.com/mount-aws-efs-file-system-on-ec2/

https://docs.aws.amazon.com/efs/latest/ug/efs-mount-helper.html#mounting-access-points

sudo mkdir /efs

sudo mount -t nfs4 -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport fs-face524e.efs.us-east-1.amazonaws.com:/ efs

fs-face524e.efs.us-east-1.amazonaws.com:/ efs nfs4 defaults,_netdev 0 0

umount -f efs

sudo mount -a

Mounting on Amazon EC2 with a DNS name

Mounting with an IP address [https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-mount-cmd-dns-name.html]

Mounting your Amazon EFS file system automatically[https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-mount-cmd-ip-addr.html]

[https://docs.aws.amazon.com/efs/latest/ug/efs-mount-helper.html#mount-fs-auto-mount-onreboot]

NFS client

nfs-utils for RHEL, CentOS, Amazon Linux, and Fedora distributions

nfs-common for Debian and Ubuntu distributions

Network File Sharing (NFS) is a protocol that allows you to share directories and files with other Linux clients over a network