CPSC4240 Midterm 1

What is the command to set permissions for a file1.c using octal form with owner having all permissions, group having read and execute, and world having nothing?

sudo chmod 750 file1.c

Why is stdin a softlink?

Where does the stdin softlink point?

/proc/self/fd/0

What is the command to create a softlink?

ln -s filename softlink_name

Which directory is the window into the hardware world?

/dev

What is a virtual machine?

software that emulates a computer system with its own virtual cpu, network interface, and storage in the user space in the existing OS as an independent process

What is the hypervisor?

the virtual machine manager (ex: UTM)

Where does a virtual machine run?

on top of the host operating system

What does AT&T stand for?

American Telephone and Telegraph

What does DARPA stand for?

defense advanced research projects agency

In which system did open source movement start?

GNU

What does GNU stand for?

GNU not Unix

Who created Linux?

Linus Torvalds

What does GPL stand for?

general public license

What is copyleft?

if you make a derivative work from something open source, it can't have a stricter license than the original

Where was Linus Torvalds from?

Finland

What is a distribution of Linux?

the kernel and packages

What family is Ubuntu in?

debian

Who created Ubuntu?

Mark Shuttleworth

What is the naming convention of Ubuntu versions?

year and month of release (ex: 24.04 = April 2024)

How many versions of Ubuntu are released a year?

two

What months are the two versions of Ubuntu released?

April and October

What release of Ubuntu has long term support every year?

April version

What is open source?

basically when the code is available to everyone so they can modify, play with, and create their own version of it

What does BIOS stand for?

basic input output system

What is BIOS?

firmware that initializes hardware on the motherboard

What does BIOS do?

gets system ready to load and run the OS

What is a hardware partition?

a logical division of hard drive

What is the naming convention of sata drive partitions?

ex: sda2, first drive, second partition

Outline the Boot process.

1. the system powers up, BIOS does hardware init

2. boot loader calls kernel

3. kernel loads initial RAM disk that loads system drives and finds root file system

4. after kernel is set, systemd init system starts

5. systemd takes over to mount host's file system and starts services

What is the name of the kernel?

vmlinuz

What does the master boot record (MBR) contain?

a table with the boot loader and partition table

Who came up with UEFI?

Intel

What does UEFI stand for?

unified extensible firmware interface

What are the password stages?

1. BIOS password

2. hard drive password

3. user password

What does GRUB stand for?

grand unified boot loader

What are the three init systems?

sysVinit, Upstart, and systemd

What are daemons?

kernel background processes that start autonomously after booting

What kinds of PIDs do daemons have?

low numbers, ex: systemd = PID 1

How can you check how long each service takes to start?

system-analyze

What are the three types of users?

root, sudoers, standard

What can each group of users do?

root = anything, standard = certain privileges (PLP), sudoer = standard user that was explicitly given permission to do something

What is the Principle of Least Privilege (PLP)?

when you give a user the least amount of privilege possible for them to complete the things they need to be able to do

What does pwd do?

print working directory

What does ls -l do?

shows everything in your directory in long list format (shows pid, parent, etc)

What does ls * do?

pattern seeking, anything you put after the , your system will pull up (ex: ls .c pulls up all .c files)

What is a process?

an instance of a computer program

What is the PCB?

process control block, data structure in the kernel with the information needed to schedule the process

What memory allocations does a process have?

data, instructions, stack, heap

What does the stack hold for a process?

function activation

What does the heap hold for a process?

dynamically allocated entities

What directory are processes in?

/proc

What is in the boot directory?

kernel (vmlinuz)

What is the first process created?

What is the process with PID 0?

the scheduler

Why can't we see PID 0 in the system?

What is the process with PID 1?

systemd

What does systemd do?

adopts ophans, reaps zombies, handles signals for children

How do processes create other processes? Is there a command?

fork()

What is an orphan process?

created when a parent dies, normally adopted by systemd

What is a zombie process?

created when a child doesn't wait() for it's parent (process has been completed but still remains in process table due to lack of correspondence between parent and child)

What does top show?

processes in real time

What does ps show?

a snapshot of processes at that moment

What does pstree show?

a snapshot that displays processes in a tree format

What does pgrap do?

returns matching PID for process

Where does a child get its niceness (priority)?

from its parent (set with nice and adjust with renice)

What is a runaway process?

a process that consumes more resources than expected

Are daemons orphans?

yes, intentionally

What does cron do?

runs commands on a schedule

What does anacron do?

runs skipped processes as soon as system boots up

What is a filesystem?

a way to organize and store files

What filesystem does our version of Linux use?

ext4

What are the most common filesystems?

Fat32, NTFS, HtS+, Btrfs, Swap FS

What did ext3 introduce?

journaling!

What is journaling?

when the system writes data to another part of the hard drive and notes the necessary changes to a log incase of a power failure or something that would cause inconsistencies

What are the three journaling levels?

jornal, ordered, writeback

Why does Linux support so many different filesystems?

because it was made to be flexible and customizable

What kinds of items live in a filesystem?

files, directories, and devices

What are the two kinds of devices?

block devices and character devices

What is a character device?

communicates with driver through stream of characters

What is a block device?

communicates with driver through fixed size blocks of data

How do you know if a device is a block or character device?

first character on the permissions string

What are the two forms of permissions?

octal and mnemonic

What are octal permissions?

the numerical way of setting permissions (ex: chmod 740 --> gives user all, group read, and other none)

What are mnemonic permissions?

the alphabetical way of changing permissions (ex: chmod u=rwx, g=r, o= filename --> gives user all, group read, and other none)

What is umass?

user mask, the default permissions for the files and directories you create (subtract from 777 or 666)

How do you see what your umass is?

command "umass"

How do you change/set your umass?

"umass number"

What is in /bin?

binaries, executables

What is in /boot?

grub, kernal image (vmlinuz)

What is in /dev?

files associated with device drivers, stdin, stdout, stderr

What is in /etc?

config files, passwd, shadow, group, sudoers, etc.

What's in /home?

holders for every user in the system

What's in /mnt?

mount point (mounting an external filesystem to yours, hiding existing files if you mount over it)

What is in /opt?

third party software (ex: zoom)

What's in /sbin?

super user binaries

What's in /usr?

everything a user might need to do their work

What's in /var?

files that vary in size like log files

What are inodes?

index nodes that are assigned by kernel when a file is created

What command displays inodes for you to see in a directory?

ls -i