Want to become a systems engineer ? If yes You should be aware about this things.

Basic Linux commands

•  grep
•  ls
•  cat
•  vi and vim
•  cut
•  find
•  dmidecod
•  lsof
•  lscpu
•  netstat 
•  df
•  du
• uname

Basic files that stores important informations

•  /proc/meminfo
•  /proc/cpinfo
•  /proc/version

Webservers that are used ,
    
            in Linux servers

• Apache/httpd webserver
• Nginx
• Lighttpd

           in Windows servers

• Microsoft Internet Informaion service (IIS)

Working of DNS 

Name resolution

Recursive resolver

Bind

Zone

Resource Records

Ports of major services

• cPanel     2082
• cPanel – SSL     2083
• WHM     2086
• WHM – SSL     2087
• Webmail     2095
• Webmail – SSL     2096
• E-MAIL
• POP3     110
• POP3 – SSL     995
• IMAP     143
• IMAP – SSL     993
• SMTP     25
• SMTP Alternate     26
• SMTP Alternate     587
• SMTP – SSL     465
• WEB
• HTTP     80
• SSL     443
• FTP     21
• FTPs     990
• SFTP     22
• SFTP Shared/Reseller Servers     2222
• Webdisk     2077
• Webdisk – SSL     2078
• MySQL     3306
• MSSQL     1433
• SSH     22
• Telnet 23