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50 Linux System Admin Questions and Answers

1. What does nslookup do?

nslookup is a network administration command-line tool available for many computer operating systems for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or for any other specific DNS record.
2. How do you display the top most process utilizing CPU process?

top will display what is using your CPU.
ps -eo pcpu,pid,user,args | sort -k1 -r | head -10 will also display the top 10 processes
3. How to check all open ports on a Linux machine and block the unused ports?

netstat -t(tcp)
netstat -u(udp)or
netstat -tulpn
to verfy the open ports
to block u have to use iptable & tcp_wrappers( hosts.deny
file)
4. What is Linux? How is it different from UNIX? 5. Explain the boot process of Unix System in details. 6. How do you change the permissions? How to create a file that’s read-only property? 7. Explain SUDO in detail. What are its disadvantages? 8. What is the difference between UDP and TCP? 9. Describe the boot order of a Linux m…