In this post, I will continue with the Linux interview questions series and share the third part of it.
- What do the following commands do and how would you use them?
- What does an
& after a command do? Also ? in bash script
- What does
& disown after a command do?
- What is a packet filter and how does it work?
- What is Virtual Memory?
- What is swap and what is it used for?
- What is an A record, an NS record, a PTR record, a CNAME record, an MX record?
- Are there any other RRs and what are they used for?
- What is a Split-Horizon DNS?
- What is the sticky bit?
- What does the immutable bit do to a file?
- What is the difference between hardlinks and symlinks? What happens when you remove the source to a symlink/hardlink?
- What is an inode and what fields are stored in an inode?
- How to force/trigger a file system check on next reboot?
- What is SNMP and what is it used for?
- What is a runlevel and how to get the current runlevel?
- What is SSH port forwarding?
- What is the difference between local and remote port forwarding?
- What are the steps to add a user to a system without using useradd/adduser?
- What is MAJOR and MINOR numbers of special files?
- Describe the mknod command and when you’d use it.
- Describe a scenario when you get a “filesystem is full” error, but ‘df’ shows there is free space.
- Describe a scenario when deleting a file, but ‘df’ not showing the space being freed.
- Describe how ‘ps’ works.
- What happens to a child process that dies and has no parent process to wait for it and what’s bad about this?
- Explain briefly each one of the process states.
- How to know which process listens on a specific port?
- What is a zombie process and what could be the cause of it?
- You run a bash script and you want to see its output on your terminal and save it to a file at the same time. How could you do it?
- Explain what echo “1” > /proc/sys/net/ipv4/ip_forward does.
- Describe briefly the steps you need to take in order to create and install a valid certificate for the site https://foo.example.com.
- Can you have several HTTPS virtual hosts sharing the same IP?
- What is a wildcard certificate?
- Which Linux file types do you know?
- What is the difference between a process and a thread? And parent and child processes after a fork system call?
- What is the difference between exec and fork?
- What is “nohup” used for?
- What is the difference between these two commands?
- How many NTP servers would you configure in your local ntp.conf?
- What does the column ‘reach’ mean in
ntpq -p output?
- You need to upgrade kernel at 100-1000 servers, how you would do this?
- How can you get Host, Channel, ID, LUN of SCSI disk?
- How can you limit process memory usage?
- What is bash quick substitution/caret replace(^x^y)?
- Do you know of any alternative shells? If so, have you used any?
- What is a tarpipe (or, how would you go about copying everything, including hardlinks and special files, from one server to another)?
- How can you tell if the httpd package was already installed? rpm -qa | grep <package name>
- How can you list the contents of a package?
- How can you determine which package is better: openssh-server-5.3p1-118.1.el6_8.x86_64 or openssh-server-6.6p1-1.el6.x86_64 ?
- Difference b/w soft link vs hard links?
- Difference b/w ~/.bash and ~/.profile files?