Adicionar registro DNS windows linha de comando

 Usando o Prompt de Comando (dnscmd)Abra o Prompt de Comando como Administrador e utilize a seguinte estrutura para adicionar um registro do tipo A (endereço IP):
dnscmd . /RecordAdd <NomeDaZona> <NomeDoHost> A <EnderecoIP>
Exemplo prático: 
dnscmd . /RecordAdd meu-dominio.com meu-servidor A 192.168.1.50

O ponto . indica que você está gerenciando o servidor DNS local.
Usando o PowerShell (Add-DnsServerResourceRecordA)
Abra o Windows PowerShell como Administrador e execute o comando correspondente para a zona de pesquisa direta:
Add-DnsServerResourceRecordA -Name <NomeDoHost> -IPv4Address <EnderecoIP> -ZoneName <NomeDaZona>
Exemplo prático: Add-DnsServerResourceRecordA -Name meu-servidor -IPv4Address 192.168.1.50 -ZoneName meu-dominio.com 

SNMP Oracle Linux

 

sudo yum install net-snmp net-snmp-utils -y 

 

nano /etc/snmp/snmpd.conf 

agentAddress  udp:10.20.1.2:161
rocommunity public

systemctl restart snmpd
 

Change 'mysql_native_password' authentication

 Plugin mysql_native_password reported: ''mysql_native_password' is deprecated and will be removed in a future release. Please use caching_sha2_password instead'


You can identify the affected users by running the following query in your MySQL console

SELECT user, host, plugin FROM mysql.user WHERE plugin='mysql_native_password';

Once you identify the users, update their authentication plugin using this command
ALTER USER 'user'@'location' IDENTIFIED WITH caching_sha2_password BY 'password';
FLUSH PRIVILEGES;

If your application or framework (such as an older version of PHP, Node.js, or a specific driver)
 does not support caching_sha2_password, you can use sha256_password as an alternative

Oracle linux security updates

 

- List available security packages:
dnf updateinfo list security
 

- List installed security updates:
dnf updateinfo list --installed --security

- Count available security updates (by severity):
dnf updateinfo summary
 

- Apply all available security updates:
sudo dnf update --security

- Apply a specific security advisory:
sudo dnf update --advisory=ELSA-YYYY-XXXX
 

- Update only specific package
sudo dnf upgrade openssh openssh-server openssh-clients 

NGINX - To allow a specific User-Agent from one IP address only

Step 1: Define the Map BlocksAdd this configuration inside the http {} block of your /etc/nginx/nginx.conf file. This logic evaluates the incoming User-Agent and IP address to flag unauthorized requests


http {
    # ... your existing http config ...

    # 1. Check if the User-Agent matches the restricted one
    map $http_user_agent $is_restricted_ua {
        default         0;
        "~*YourCustomUserAgent" 1; # Replace with your target User-Agent (regex matching)
    }

    # 2. Check if the client IP is NOT the authorized one
    map $remote_addr $is_unauthorized_ip {
        default        1;
        "192.168.1.50" 0; # Replace with your ONLY allowed IP address
    }

    # 3. Combine both conditions: Flag if it's the target UA AND an unauthorized IP
    map "$is_restricted_ua$is_unauthorized_ip" $block_request {
        default   0;
        "11"      1; # 1 (Restricted UA) + 1 (Unauthorized IP) = Block
    }
}



Step 2: Apply the Block RuleOpen your website's specific server configuration file (e.g., inside /etc/nginx/sites-available/) and use the combined variable to reject requests with a 403 Forbidden error.

server {
    listen 80;
    server_name yourdomain.com;

    # Place this rule globally inside the server block or inside a specific location block
    if ($block_request) {
        return 403;
    }

    location / {
        # ... your standard site configuration ...
    }
}

TLS/SSL certificate CSR

 
# CSR
openssl req -new -newkey rsa:4096 -keyout domain.key -out domain.csr


# Remove key password
openssl rsa -in encrypted.key -out decrypted.key


chain = crt + intermediary

Certificate - PEM to PKCS12

 

Convert Lets encrypt PEM to tomcat PKCS12 

openssl pkcs12 -export \ -in fullchain.pem \ -inkey privkey.pem \ -out server.p12 \ -name my-domain-alias