dominis / interview-questions

Collection of technical questions I was asked on job interviews

Interview Questisons

I mostly apply to devops / sysops / sys engineer / release engineer / automatization engineer jobs.

Here you can find my up to date cv

List of questions:

• Difference between apache and nginx?

  https://www.digitalocean.com/community/tutorials/apache-vs-nginx-practical-considerations

• If you wanted to find the procedures that a Linux program executes, what tool could you use?

  http://linux.die.net/man/1/strace

• From the shell, what built-in function would you use to replace the current process with its argument(s)?

  http://linux.die.net/man/1/xargs

• What file would you edit if you wanted to change the ordering of which name systems are consulted?

  http://linux.die.net/man/5/resolv.conf

• What are the three types of messages issued while establishing a TCP connection?

  http://www.tcpipguide.com/free/t_TCPConnectionEstablishmentProcessTheThreeWayHandsh-3.htm

• In a reverse HTTP proxy, to which header is customary to add the remote IP address in the new request?

  https://en.wikipedia.org/wiki/X-Forwarded-For

• Which Elasticsearch API would you call to get the JVM versions of all running nodes?

  https://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-nodes-info.html

• Describe how PXE works

  https://en.wikipedia.org/wiki/Preboot_Execution_Environment

• Talk aobut TFTP

  https://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol

• How would you change the resolv.conf on 20 machines in the same time?

  for HOST in $(cat servers.txt ) ; do ssh $HOST "echo nameserver 1.1.1.1 > /etc/resolv.conf" ; done

• How would you do this on thousands faster?

  for HOST in $(cat servers.txt ) ; do ssh $HOST "echo nameserver 1.1.1.1 > /etc/resolv.conf" & ; done http://unix.stackexchange.com/a/103734

• What tool would you use to change the existing line in resolv.conf?

  http://linux.die.net/man/1/sed

• You have 10 webservers how would you tell the top10 ip addresses from their access log

  For ten servers you can use the for loop above with this command: awk '{ print $1 }' access.log | sort | uniq -c | sort -nr | head -10

• How would you do that on thousands of servers

  Here you can talk about centralized log collection or event based logging http://www.rsyslog.com/ https://www.elastic.co/webinars/introduction-elk-stack

• Talk about the major RAID types

  http://www.tonypickett.com/wp-content/uploads/2013/12/allraid.png

• What is a zombie process?

  https://en.wikipedia.org/wiki/Zombie_process

• What is an ephemeral port?

  https://en.wikipedia.org/wiki/Ephemeral_port

• What limits the maximum number of connections on a linux server?

  http://stackoverflow.com/a/2332756

• How netstat works?

  http://linuxcommand.org/man_pages/netstat8.html

• How traceroute works?

  https://ccieblog.co.uk/basic-troubleshooting-commands/how-does-traceroute-work

• What process has PID 0 and PID 1?

  http://unix.stackexchange.com/a/145581

• What is /proc?

  http://linux.die.net/man/5/proc

• What is the difference between ext2 ext3 and ext4 filesystems?

  http://www.thegeekstuff.com/2011/05/ext2-ext3-ext4/

• Why is a battery on a RAID controller?

  http://serverfault.com/a/203361

• How would you fix chmod a-x -Rf /bin?

  http://unix.stackexchange.com/questions/83862/how-to-chmod-without-usr-bin-chmod