Basic Linux Commands

Question 1

Linux commands

Answer 1

• The command line - Terminal, XTerm, or similar

• Commands are similar in both Linux and Mac OS
• Mac OS derived from
BSD (Berkeley Software Distribution) Unix
• This section is specific to Linux

• Download a Live CD or install a virtual machine
  
  • Many pre-made Linux distributions are available
  • I’m using Ubuntu in a virtual machine
• Use the man command for help
  
  • An online manual
  • > man grep

Question 2

ls

Answer 2

• List directory contents
  
  • Similar to the dir command in Windows

• Lists files, directories
• May support color coding;
• Blue is a directory,
red is an archive file, etc.

• For long output, pipe through more:
  
  • > ls -l | more
  • (use q or Ctrl-c to exit)

Question 3

grep

Answer 3

• Find text in a file
  
  • Search through many files at a time
  • grep PATTERN [FILE]
  • > grep failed auth.log

Question 4

cd

Answer 4

• Change current directory
  
  • Nearly identical to Windows command line
  • Forward slashes instead of backward
• cd
  
  • > cd /var/log

Question 5

shutdown

Answer 5

• Shut the system down
  
  • Safely turn off the computer in software
  • Similar to the Windows shutdown command

•sudo shutdown 2
• Shuts down and turns off the computer
in two minutes

• sudo shutdown -r 2
  
  • Shuts down and reboots in two minutes
  • Important when you’re not on site

•Ctrl-C to cancel

Question 6

pwd

Answer 6

• Print Working Directory
• Displays the current working directory path
• Useful when changing directories ofte

Question 7

passwd

Answer 7

• Change a user account password
• Yours or another
• passwd [username]

Question 8

mv

Answer 8

• Move a file
  
  • Rename a file
• mv SOURCE DEST
  
  • > mv first.txt second.txt

Question 9

cp

Answer 9

• Copy a file
  
  • Duplicate files or directories
• cp SOURCE DEST
  
  • > cp first.txt second.txt

Question 10

rm

Answer 10

• Remove files or directories
  
  • Deletes the files

• Does not remove directories by default
• Directories must be empty to be removed or
must be removed with -r

Question 11

mkdir

Answer 11

• Make a directory
  
  • Create a folder for file storage
• mkdir DIRECTORY
  
  • > mkdir notes

Question 12

chmod

Answer 12

• Change mode of a file system object
  • r=read, w=write, x=execute
  • Can also use octal notation
  • Set for the file owner (u), the group(g),
     others(o), or all(a)

• chmod mode FILE
  
  • > chmod 744 script.sh
• chmod 744 first.txt
  
  • User; read, write execute
  • Group; read only
  • Other; read only
• chmod a-w first.txt
  
  • All users, no writing to first.txt
• chmod u+x script.sh
  
  • The owner of script.sh can execute the file

Question 13

chown

Answer 13

• Change file owner and group
  
  • Modify file settings
• sudo chown [OWNER:GROUP] file
  
  • > sudo chown professor script.sh

Question 14

•iwconfig

Answer 14

• View or change wireless network configuration
• essid, frequency/channel, mode, rate, etc.
• Requires some knowledge of the wireless network
• iwconfig eth0 essid studio-wireless

Question 15

•ifconfig

Answer 15

• View or configure a network interface and
IP configuration
•ifconfig eth0

Question 16

ps

Answer 16

• View the current processes
  
  • And the process ID (PID)
  • Similar to the Windows Task Manager
• View user processes
  
  • ps
• View all processes
  
  • ps -e | more

Question 17

su / sudo

Answer 17

• Some command require elevated rights

* There are some things normal users can’t do

Question 18

•su

Answer 18

• Become super user
• Or change to a different user
• You continue to be that user until you exit

Question 19

•sudo

Answer 19

• Execute a command as the super user
• Or as a different user ID
• Only that command executes as the super user

Question 20

apt-get

Answer 20

• Advanced Packaging Tool
  
  • Handles the management of application packages
  • Applications and utilities
• Install, update, remove
  
  • > sudo apt-get install wireshark

Question 21

vi

Answer 21

• Visual mode editor
  
  • Full screen editing with copy, paste, and more
• vi FILE
  
  • > vi script.sh

Question 22

• Insert tex

Answer 22

• i
• Exit insert mode with Esc
• Save (write) the file and quit vi
• :wq

Question 23

dd

Answer 23

• Convert and copy a file
• Backup and restore an entire partition
• > dd if= of=

[Options]
• Creating a disk image
•> dd if=/dev/sda of=/tmp/sda-image.img
• Restoring from an image
•> dd if=/tmp/sda-image.img of=/dev/sda

Question 24

Closing programs

Answer 24

• Use terminal - sudo for proper permissions

• killall
• sudo killall firefox
• xkill
• Graphical kill

•kill

Question 25

A user calls the helpdesk wanting a simple method he can use for backing up multiple large directories on a Linux system. What command allows users to back up and compress large directories?

Answer 25

tar