linux-sysadmin-interview-questions

A collection of linux sysadmin/devop interview questions. Feel free to contribute via pull requests, issues or email messages.

Table of Contents

1. Contributors
2. General Questions
3. Simple Linux Questions
4. Medium Linux Questions
5. Hard Linux Questions
6. Networking Questions
7. DevOp Questions
8. Fun Questions
9. Demo Time
10. Puppet Specific
11. Other Great References

####[⬆] Contributors:

• @moregeek

The majority of the questions were collected from:

• https://github.com/gurmeet1109/docgurmeet/tree/master/InterviewQuestionsSamples
• https://github.com/kylejohnson/linux-sysadmin-interview-questions/blob/master/test.md

####[⬆] General Questions:

• What did you learn yesterday/this week?
• Talk about your preferred development/administration environment. (OS, Editor, Browsers, Tools etc.)
• What function does DNS play on a network?
• What is a proxy and how does it work?
• What is HTTP?
• What is SMTP? Give the basic scenario of how a mail message is delivered via SMTP?
• What is RAID? What is RAID0, RAID1, RAID5, RAID10?
• What is a level 0 backup? What is an incremental backup?
• Describe the general file system hierarchy of a Linux system.

####[⬆] Simple Linux Questions:

• What is the name and the UID of the administrator user?
• How to list all files, including hidden one, in a directory?
• What is the Unix/Linux command to remove a directory and its contents?
• What command will show you free/used memory? Does free memory exists on linux?
• How to search for the string "my konfi is the best" in files of a directory recursively?
• How to connect to a remote server or what is SSH?
• How to get all environment variables and how can you use them?
• I get "command not found" for ifconfig -a. What can be wrong?
• What happens if I type TAB-TAB?
• What command will show the available disk space on the Unix/Linux system?
• What command is used to lookup DNS records?
• What Unix/Linux commands will alter a file's ownership, file's permissions?
• What does the permission 0750 on a file mean?
• What does the permission 0750 on a directory mean?
• How to add a new system user without login permissions?
• How to add/remove a group from a user?

####[⬆] Medium Linux Questions:

• What does the tee command?
• What does the awk command?
• What does the tr command?
• What does the cut command?
• What does the tuc command?
• What does a & after a command do?
• What is a packet filter and how does it work?
• What is swap and what is it used for?
• What is an A record, a NS record, a PTR record, a CNAME record, a MX record?
• What is the sticky bit?
• What is the difference between hardlink and symlink? What happens when you remove the source to a symlink/hardlink?
• Howto force/trigger a file system check on next reboot?

####[⬆] Hard Linux Questions:

• What is the difference between processes and threads?
• What is a tunnel and how you can bypass a http proxy?
• What is the difference between IDS and IPS?
• What shortcuts do you use on a regular basis?
• What is the linux standard base?
• What is an atomic operation?
• Your fresh configured http server is not running after a restart, what can you do?
• What kind of keys are in ssh/authorized_keys and what it is used for?
• I've added my public ssh key into authorized_keys but I'm still getting a password prompt, what can be wrong?
• Did you ever create RPM's, DEB's or solaris pkg's?

####[⬆] Networking Questions:

• What command is used to show all open ports and/or socket connections on a machine?
• Is 300.168.0.123 a valid IPv4 address?
• Which IP ranges/subnets are "private" or "non-routable" (RFC 1918)?
• What is a VLAN?
• What is ARP and what is it used for?
• What is the difference between TCP and UDP?
• What is the purpose of a default gateway?
• What command is used to show the route table for a machine?
• A TCP connection on a network can be uniquely defined by 4 things. What are those things?
• When a client running a web browser connects to a web server, what is the source port and what is the destination port of the connection?
• How do you add an IPv6 address to a specific interface?
• You have added an IPv4 and IPv6 address to interface eth0. A ping to the v4 address is working but a ping to the v6 address gives yout the response sendmg: operation not permitted. What could be wrong?

####[⬆] DevOp Questions:

• Can you describe your workflow when you create a script?
• What is GIT?
• What is a dynamically/statically linked file?
• What is "configure && make && make install"
• What is puppet/chef/ansible used for?
• How do you create a new mysql user?
• How do you create a new postgres user?
• What is a virtual IP address? What is a cluster?

####[⬆] Fun Questions:

• A careless sysadmin executes the following command: chmod 444 chmod - what do you do to fix this?
• I've lost my root password, what can I do?
• I've rebooted a remote server but after 10 minutes I'm still not able to ssh into it, what can be wrong?

####[⬆] Demo Time:

• Unpack test.tar.gz without man pages or google.
• Remove all "*.pyc" files from testdir recursively?
• Search for "my konfu is the best" in all *.py files.
• Replace the occurrence of "my konfu is the best" with "I'm a linux jedi master" in all *.txt files.
• ⁉️ more on files ... cut, tr, awk ...
• Test port 443 on a machine with IP address X.X.X.X is reachable.
• Get http://myinternal.webserver.local/test.html via telnet.
• How to send an email without a mail client, just on the command line?
• Write a get_prim python/perl/bash/pseudo script.

####[⬆] Puppet Specific:

• What is a defined type?
• What is containment?
• What is your understanding of roles and profiles in Puppet?

####[⬆] Other Great References:

Some questions are 'borrowed' from other great references like:

• https://github.com/darcyclarke/Front-end-Developer-Interview-Questions
• https://github.com/kylejohnson/linux-sysadmin-interview-questions/blob/master/test.md
• https://github.com/gurmeet1109/docgurmeet/tree/master/InterviewQuestionsSamples