IT-OS-Admin-Linux

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• RHEL: https://www.redhat.com/en/services/training/rh024-red-hat-linux-technical-overview

SSH

sudo dnf install openssh-client
sudo dnf install openssh-server
sudo systemctl restart sshd.service
sudo systemctl enable sshd.service
..
# Key-Typs: RSA algorithm and DSA algorithm.
$HOME/.ssh/id_rsa               # The file contains the RSA private key.
$HOME/.ssh/id_rsa.pub           # The file contains the RSA public key.
$HOME/.ssh/authorized_keys      # The file contains the keys that can be used for logging into system.
..
sudo nano /etc/ssh/ssh_config
sudo nano /etc/ssh/sshd_config
------------------------------
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile %h/.ssh/authorized_keys
PasswordAuthentication no      # Yes: Can login with Password; No: Can’t login with Password
------------------------------
/etc/init.d/ssh restart
..
ssh-keygen -t rsa -b 4096 -C "samerhijazi@hotmail.com"	# Generate prv and pub Key
ssh-copy-id –i id_rsa.pub user@hostname			# Copy Pub-Key to server
ssh –i id_rsa user@hotname				# Login server with prv-key
..or
cat ~/.ssh/id_rsa.pub | ssh user@hostname "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
ssh user@hostname "echo `cat ~/.ssh/id_rsa.pub` >> ~/.ssh/authorized_keys"

Setting Firewall

Service

$ sudo systemctl disable firewalld
$ sudo systemctl stop firewalld
$ sudo systemctl disable NetworkManager
$ sudo systemctl stop NetworkManager
$ sudo systemctl enable network
$ sudo systemctl start network

Zone

sudo firewall-cmd --get-zones
sudo firewall-cmd --get-active-zones
sudo firewall-cmd --get-default-zone
sudo firewall-cmd --get-services
sudo firewall-cmd --list-all
sudo firewall-cmd --list-ports

Zone-home

sudo firewall-cmd --zone=home --list-all
sudo firewall-cmd --zone=home --list-ports
sudo firewall-cmd --zone=home --list-services

Setting

sudo firewall-cmd --set-default-zone=home
sudo firewall-cmd --zone=home --change-interface=eth0
sudo firewall-cmd --zone=home --add-service=http
sudo firewall-cmd --zone=home --add-port=80/tcp --permanent

New Zone "boxblue"

sudo firewall-cmd --permanent --new-zone=boxblue
sudo firewall-cmd --permanent --zone=boxblue --add-service=ssh
sudo firewall-cmd --permanent --zone=boxblue --add-service=http
sudo firewall-cmd --permanent --zone=boxblue --add-service=https
sudo firewall-cmd --permanent --zone=boxblue --add-port=80/tcp
sudo firewall-cmd --permanent --zone=boxblue --add-port=22/tcp
sudo firewall-cmd --permanent --zone=boxblue --change-interface=wlp0s19f2u1
sudo firewall-cmd --permanent --set-default-zone=boxblue

Update

sudo firewall-cmd --reload
sudo systemctl restart network
sudo systemctl reload firewalld

Vim

Source: https://vim.rtorr.com/

Esc  Exit the current mode into the “command mode”.
i    Enter “Insert mode” for inserting text.
v    Enter "Visual mode" for character.
V    Enter "Visual mode" for line.

:    “Last-line mode” where Vim expects you to enter a command such as to save the document. 

h    Move Left
j    Move Down
k    Move Up
l    Move Right

u    Undo the last operation.
d    Delete or Cut selected item.
y    Copy selected item.
p    Paste storage buffer after the cursor.

:q	Quit Vim but fails when file has been changed
:q!	Quit Vim without saving the changes to the file.
:w	Save the file
:wq	Save the file and quit Vim.
:w name Save the file with the new_name filename