Unix/Linux Fundamentals

Flashcards based on lecture notes on Unix/Linux operating systems.

Unix philosophy

Unix systems are characterized by a modular design that is sometimes called the what?

Coreutils

The unix operating system should provide a set of simple tools known as?

Linux

What is the name of the GNU kernel?

Bourne Shell

The POSIX shell is the same as which shell?

Bourne again shell (BASH)

What is the default shell on GNU/Linux?

False

True or False: The CLI, terminal, and shell are just different names for the same thing.

/

What is the root of the filesystem?

Root

What is the name of the user that lives in kernel land?

/root

What is the home directory of the root user?

A user that is allowed to run commands as root

What is the administrator on a Linux system?

Interface that allows software to interact with external hardware.

What is a device driver?

Kernel-mode device drivers and User-mode device drivers

What are two types of device drivers?

/var/log

Where are log files kept?

/etc

Where are system configuration files located?

False

True or False: the /usr/bin directory contains required binaries.

The home directory of the user

What is the ~ for?

The current directory

What is a single dot short for?

/

Where does the absolute path for a file or directory start?

System calls

What is the fundamental interface between an application and the Linux kernel?

ausyscall —dump | less

What is the command to pull up system calls by number on a Linux machine?

glibc

What is the name of the C library on GNU/Linux called?

elf

What is the file type for executable files in Unix/Linux?

glibc

Wha is the GNU C library called?

Used to map the file to memory

What does the mmap system call do?

False

True or False: a reboot is required when one installs an LKM

lsmod

What is the command to list loaded kernel modules?

Kernel object

What does the .ko file extension stand for?

-ef

What are some of the common arguments used with the ps command?

Daemons

What is a type of process that runs in the background without any human interaction?

Login, interactive, and non-interactive

What are the three types of login shells?

Interactive

What shell actively reads commands from user input?

-, -l, —login

What argument is used with the “su” command to open a BASH login?

-l, —login

What argument opens a BASH login with the “bash” command?

rbash

What is the restricted BASH shell called?

env or printenv

What command is used to print environmental variables?

PATH

What environmental variable is checked when we execute a command in the shell?

Remote login and command line execution

SSH’s most notable applications are what?

Secure copy (scp)

Name one file transfer protocol based on SSH.

A regular user that is allowed to run commands as root with the sudo command

What is an administrator account?

Service accounts

What type of account do users like Apache have?

System account

What type of accounts belong to users like sys or a daemon?

/etc/passwd

What file contains user information?

/etc/shadow

Where are user password hashes stored?

~/.bashrc

Where are local user configurations stored?

Principle of least privilege

What restricts the rights and access of a user to the minimal amount required to perform their role?

Individual accounts

What element of user management says administrators of a system should not share accounts?

Require the password to be changed periodically, do not allow the reuse of old passwords, require that they be of some level of complexity

What are some of the basics of password management?

ping

What command is used to check network connectivity?

route

What command is used to display the routing table?

IP of Host, IP Default Gateway, Subnet or CIDR

What information do you need to configure an IP address?

Networkctl, nmtui, nmcli

What are three command line tools used to interact with Networkd?

Daemon

The d after a process name in Networkd stands for what?

SMB & CIFS

Samba’s functionality comes from what two protocols?

smb.conf

Samba security modes are set in which file?

Share-Level & User-Level

What are the two security modes in Samba?

TCP/IP

What protocol does LDAP sit on top of?

Active directory & OpenLDAP

What are two common implementations of LDAP?

Linux

The majority of Apache servers run on what system?

/var/www/html

Where is the index.html file located?

> & <

What are the symbols used to denote request and response headers?

200 OK

What code means everything worked correctly?

Targets

SystemV has run levels, what did SystemD migrate to?

/etc/init-

In SystemV Linux, what is the centralized configuration file?

apt

What is the Debian package manager called?

metadata

A package is a container for?

crontab -e

What command is used to edit the crontab?

Minute of the hour, hour of the day, day of the month, month of the year, day of the week

What is each field of the crontab?

tar -xf

How do you unzip a Tar file?

gunzip

How do you unzip a .gz file?

cat <file> | egrep -o '([0-9]{1,3}\.){3}[0-9]{1,3}' | sort | uniq -c

Command to utilize when trying to find and count how many times an IP is listed: