Linux Best Services – Definitions, Ports, and Config Files (For Students & Interviews)

1. SSH (Secure Shell)

Definition: Used for remote login to Linux servers securely.
Port: 22
Service Name: sshd
Configuration File: /etc/ssh/sshd_config

2. HTTP (Web Server – Apache/Nginx)

Definition: Serves websites and web applications.
Port: 80 (HTTP), 443 (HTTPS)
Service Name: httpd (Apache), nginx (Nginx)
Configuration File: /etc/httpd/conf/httpd.conf (Apache), /etc/nginx/nginx.conf (Nginx)

3. FTP (File Transfer Protocol)

Definition: Used to transfer files between servers.
Port: 21
Service Name: vsftpd or proftpd
Configuration File: /etc/vsftpd/vsftpd.conf

4. DNS (Domain Name System – BIND)

Definition: Resolves domain names to IP addresses.
Port: 53
Service Name: named
Configuration File: /etc/named.conf

5. SMTP (Mail Server – Postfix/Sendmail)

Definition: Sends and relays emails.
Port: 25 (SMTP), 587 (Submission), 465 (SMTPS)
Service Name: postfix or sendmail
Configuration File: /etc/postfix/main.cf or /etc/mail/sendmail.cf

6. NTP/Chrony (Time Sync)

Definition: Synchronizes system time with network time servers.
Port: 123
Service Name: ntpd or chronyd
Configuration File: /etc/ntp.conf or /etc/chrony.conf

7. MySQL/MariaDB (Database Service)

Definition: Stores and manages databases.
Port: 3306
Service Name: mysqld or mariadb
Configuration File: /etc/my.cnf

8. Samba (File Sharing with Windows)

Definition: Shares files and printers with Windows systems.
Port: 137, 138, 139, 445
Service Name: smb
Configuration File: /etc/samba/smb.conf

9. DHCP (Dynamic Host Configuration Protocol)

Definition: Provides automatic IP addresses to clients.
Port: 67 (Server), 68 (Client)
Service Name: dhcpd
Configuration File: /etc/dhcp/dhcpd.conf

10. SNMP (Simple Network Management Protocol)

Definition: Used for monitoring network devices and servers.
Port: 161 (Query), 162 (Trap)
Service Name: snmpd
Configuration File: /etc/snmp/snmpd.conf