Interview questions 3 for Linux System Administrator

Q:16 What are the default ports used for SMTP,DNS,FTP,DHCP,SSH and squid ?

  SMTP         25
  DNS           53
  FTP            20 (data transfer) , 21 ( Connection established)
  DHCP        67/UDP(dhcp server) , 68/UDP(dhcp client)
  SSH           22
  Squid         3128


Q:17 How to check default route and routing table ?

Ans: Using the Commands ‘netstat -nr’ and ‘route -n’ we can see the default route and routing tables.


Q:18 How to check which ports are listening in my Linux Server ?

Ans:  Use the Command ‘netstat –listen’ and ‘lsof -i’


 
Q.19. How to install rpm?
 
Ans: rpm -ivh ***.rpm

 
Q20. How to add or delete a route in your System?
 
Ans: route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254
    route del -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254

 
Q21. How to give all permission for all user of a file?
 
    Ans: chmod 777 filename

 
Q22. How to check whether pptpd rpm installed or not?
 
     Ans: rpm -qa|grep pptpd

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