• 45-minute systems interview, focus on responding to real world problems with an unhealthy service, such as a web server or database. The interview will start off at a high level troubleshooting a likely scenario, dig deeper to find the cause and some possible solutions for it. The goal is to probe your knowledge of systems at scale and under load, so keep in mind the challenges of the Facebook environment.
• Focus on things such as tooling, memory management and unix process lifecycle.
More specifically, linux troubleshooting and debugging. Understanding things like memory, io, cpu, shell, memory etc. would be pretty helpful. Knowing how to actually write a unix shell would also be a good idea. What tools might you use to debug something? On another note, this interview will likely push your boundaries of what you know (and how to implement it).
Interview is all about taking an ambiguous question of how you might build a system and letting
Just run this from your Mac terminal and it'll drop you in a container with full permissions on the Docker VM. This also works for Docker for Windows for getting in Moby Linux VM (doesn't work for Windows Containers).
docker run -it --rm --privileged --pid=host justincormack/nsenter1
more info: https://github.com/justincormack/nsenter1
| #It's not directly mentioned in the documentation on how to do this, so here you go. This command will tunnel everything including DNS: | |
| sshuttle --dns -vr user@yourserver.com 0/0 --ssh-cmd 'ssh -i /your/key/path.pem' |
| node { | |
| echo 'Results included as an inline comment exactly how they are returned as of Jenkins 2.121, with $BUILD_NUMBER = 1' | |
| echo 'No quotes, pipeline command in single quotes' | |
| sh 'echo $BUILD_NUMBER' // 1 | |
| echo 'Double quotes are silently dropped' | |
| sh 'echo "$BUILD_NUMBER"' // 1 | |
| echo 'Even escaped with a single backslash they are dropped' | |
| sh 'echo \"$BUILD_NUMBER\"' // 1 | |
| echo 'Using two backslashes, the quotes are preserved' | |
| sh 'echo \\"$BUILD_NUMBER\\"' // "1" |
Picking the right architecture = Picking the right battles + Managing trade-offs
- Clarify and agree on the scope of the system
- User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?
When hosting our web applications, we often have one public IP
address (i.e., an IP address visible to the outside world)
using which we want to host multiple web apps. For example, one
may wants to host three different web apps respectively for
example1.com, example2.com, and example1.com/images on
the same machine using a single IP address.
How can we do that? Well, the good news is Internet browsers
| #!/bin/sh | |
| parse_yaml() { | |
| local prefix=$2 | |
| local s='[[:space:]]*' w='[a-zA-Z0-9_]*' fs=$(echo @|tr @ '\034') | |
| sed -ne "s|^\($s\)\($w\)$s:$s\"\(.*\)\"$s\$|\1$fs\2$fs\3|p" \ | |
| -e "s|^\($s\)\($w\)$s:$s\(.*\)$s\$|\1$fs\2$fs\3|p" $1 | | |
| awk -F$fs '{ | |
| indent = length($1)/2; | |
| vname[indent] = $2; | |
| for (i in vname) {if (i > indent) {delete vname[i]}} |
I wanted to be really able to explain to a fair amount of detail how does the program ls actually work right from the moment you type the command name and hit ENTER. What goes on in user space and and in kernel space? This is my attempt and what I have learned so far on Linux (Fedora 19, 3.x kernel).
How does the shell find the location of 'ls' ?