Cheatsheet: Linux Internals
- PDF Link: cheatsheet-linuxinternals-A4.pdf, Category: interview
- Blog URL: https://cheatsheet.dennyzhang.com/cheatsheet-linuxinternals-A4
- Related posts: CheatSheet: Leetcode For Code Interview, CheatSheet: Well-Known Papers For IT Industry, #denny-cheatsheets
1.1 Reference
1.2 Top 25 Linux Basic Questions
| Num | Name | Summary |
|---|---|---|
| 1 | Thead VS Process | Github Link |
| 2 | Explain virtual memory | Github Link |
| 3 | Explain paging and paging fault | Github Link |
| 4 | Explain inode | Github Link |
| 5 | epoll VS poll VS select | Github Link |
| 6 | Explain how OS schedules processes | Github Link |
| 7 | Explain spinlock | Github Link |
| 8 | Explain linux virtual filesystem | Github Link |
| 9 | Explain linux signal | Github Link |
| 10 | Explain RAID | Github Link |
| 11 | Explain linux fork | |
| 12 | What is /proc directory? | |
| 13 | Forget root password. How to reset it? | Reset from GRUB or liveCD |
| 14 | How to solve ssh “Connection refused” errors? | |
| 15 | How to daemonize a process? | |
| 16 | What are common scenarios of linux kernel panics? | |
| 17 | What are coredump and kdump? | |
| 18 | Program startup process in userspace | Link: Program startup process in userspace |
| 19 | What’s your favorite shell and why? | Link: Bash vs Zsh |
| 20 | Figure out who has logged to server now and previously? | w, last, lastb; lastlog; /var/run/*tmp |
| 21 | What is init program? | |
| 22 | How does sudo work? Given sudo, why people may need su? |
|
| 23 | How to close stdin/stdout/stderr of one command | some_command </dev/null >/dev/null 2>&1 |
1.3 Explain Top Linux Tooling
| Num | Name | Summary |
|---|---|---|
| 1 | Explain the output of vmstat command |
Github Link |
| 2 | Explain the output of netstat command |
Github Link |
| 3 | Explain the output of free command |
Github Link |
| 4 | Explain the output of top command |
Github Link |
| 5 | Explain the output of sar command |
system staticstics with sysstat cronjob |
1.4 Top 15 Linux Workflow
| Num | Name | Summary |
|---|---|---|
| 1 | What happens, when opening https://www.google.com | Github Link |
| 2 | What happens, when “ls -l *” | Github Link. shell, expansion, fork |
| 3 | What happens, when “Ctrl + c” in a terminal | Github Link. i/o interrupt, SIGINT, sig handler |
| 4 | What happens, when “touch a.txt” | Github Link |
| 5 | What happens, when you press power on button in a server? | Github Link. bios, mbr, grub, init, runlevel |
| 6 | What happens, when “cat /etc/hosts” | Github Link |
| 7 | Explain how system call works | Github Link |
| 8 | Explain hostname to ip address mapping workflow | Github Link |
| 9 | Explain init.d workflow | Github Link |
| 10 | Explain how to build a linux release | Github Link |
| 11 | Explain how kernel schedules process | Github Link |
| 12 | Explain how kernel read data from disk | Github Link |
| 13 | Explain how systemtap works | Github Link |
| 14 | Explain how I/O interrupt works | Github Link. Top half, bottom half, interrupt handler |
| 15 | Speed up I/O | Linux sendfile with zero-copy, mmap: map file to ram |
1.5 Top 20 Linux Advanced Questions
| Num | Name | Summary |
|---|---|---|
| 1 | Explain Linux security model | nothing-or-all model, capability, extended attributes, selinux, etc |
| 2 | Whether it’s possible to sniff HTTPS traffic? And why? | |
| 3 | Figure out what critical commands ssh users have issued? | |
| 4 | Why is I/O uninterruptible? | |
| 5 | Explain shell features | shell pipes, filename wildcards, env var expansion, alias, etc |
| 6 | What is the difference between UNIX and Linux | |
| 7 | High memory vs Low memory | Wikipedia: High memory |
| 8 | What is localhost and why would ping localhost fail? | |
| 9 | How does the Linux kernel handle a system call | Link: System calls in the Linux kernel |
| 10 | Difference between ext3 and ext4 | |
| 11 | How do you feel about systemd? | Init processes start serially, long booting time |
| 12 | ssh port forwarding VS ssh reverse port forwarding | |
| 13 | How to quickly crash an linux machine? | |
| 14 | How to deprovision a user completely? | |
| 15 | How reliable history command is? And how to alleviate the problem? |
~/.bash_history, $HISTTIMEFORMAT env |
| 16 | how to generate a zombie process | |
| 17 | With bg in one terminal, jobs doesn’t show in another terminal |
|
| 18 | How to setup http proxy with SLA for different traffic? | |
| 19 | What’s your wishlist for linux? | |
| 20 | What’s your ideal monitoring system in your imagination? |
1.6 Top 10 SRE Questions
| Num | Name | Summary |
|---|---|---|
| 1 | [Logging] | |
| 2 | [Monitoring] | |
| 3 | [Migration] Regional failure | |
| 4 | [Deployment] How to do a online rolling upgrade for a given system? | Single node, or multiple node? |
| 5 | [HA] DB | |
| 6 | [Automation] | |
| 7 | [Migration] How you migrate legacy on-prem app to cloud-native in public cloud? | |
| 8 | Incident Response and Management | |
| 9 | [Auto Scaling] | Link: Auto scaling Pinterest |
1.7 Good Mindsets
| Num | Name | Summary |
|---|---|---|
| 1 | First thing: Stop The Bleed |
|
| 2 | Pets VS Cattles | |
| 3 | Fix a process VS Fix a problem | |
| 4 | Evaluate Business Impact First | |
| 5 | Prevention VS Treatment | |
| 6 | Postmortem Culture | |
| 7 | Understand Workflow & Use Cases | Super important for trouble shooting |
| 8 | Automation VS Convention | |
| 9 | Principle Of Least Privilege | |
| 10 | Design Tools VS Use Tools | Operational knowledge is not good enough |
1.8 Top 20 Container Questions
| Num | Name | Summary |
|---|---|---|
| 1 | Compare to Linux process, what things containers can’t support? | |
| 2 | How to sniff container’s traffic? | |
| 3 | Explain the workflow of “docker stop $containerid“ |
