Users, Interactive and Login shells

Question 1

What configuration scripts are executed upon signing in through the login shell?

Answer 1

1 /etc/profile - sets up environment variables
2 ~/.bash_profile | ~/.bash_login | ~/.profile - first file executed, sets up user env variables
3 ~/.bashrc - sets up user created functions and command aliases
4 /etc/bashrc - sets up system wide functions and command aliases

Question 2

What script will be executed at user logout if it exists?

Answer 2

~/.bash_logout

*user defined commands can be placed here to perform actions at logout

Question 3

What configuration scripts are executed upon opening a non login shell (interactive)?

Answer 3

1 ~/.bashrc - sets up user created functions and commands

2 /etc/bashrc - sets up system wide functions and command aliases

Question 4

How do you modify the $PATH env variable?

Answer 4

append: PATH=$PATH:/directory
prepend: PATH=/directory:$PATH

Question 5

How do you create a variable and use it in other shells?

Answer 5

export VARIABLENAME

Question 6

What is the structure that constitutes a command?

Answer 6

Command Option Argument

i.e ls -l file

Question 7

What is the command to create an alias?

Answer 7

alias =’’

i.e alias lr=’ls -R’

Question 8

What is the command to remove a created alias?

Answer 8

unalias

i.e unalias lr

Question 9

How do you create a persistent alias?

Answer 9

Append alias to ~/.bashrc

Question 10

How do you get a listing of shell and environment variables?

Answer 10

set

Question 11

When using the su command, what denotes a login shell?

Answer 11

-

• l
• -login
  i. e su - *loads the env variables for the user

Question 12

What is important to account for when running a script?

Answer 12

Script is run with under user with login shell, for instance if it depended on environment variables that were not present from interactive shell

Question 13

How would you login as root without knowing the root user password?

Answer 13

sudo su