1.11 - Linux Commands

Question 1

Linux commands

Answer 1

• The command line - Terminal, XTerm, or similar
• Commands are similar in both Linux and macOS
  – 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
• Use the man command for help - An online manual
  > man grep

Question 2

Bash - 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

Bash - pwd

Answer 3

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

Question 4

Bash - mv

Answer 4

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

Question 5

Bash - cp

Answer 5

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

Question 6

Bash - rm

Answer 6

• 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 7

Bash - chown

Answer 7

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

Question 8

Bash - su / sudo

Answer 8

• Some commands require elevated rights
• sudo
  – Execute a command as the super user or user ID
  – Only that command executes as the super user
• su
  – Become super user or change to a different user
  – You continue to be that user until you exit

Question 9

Bash - chmod

Answer 9

• 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 10

Bash - apt-get

Answer 10

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

Question 11

Bash - yum

Answer 11

• Yellowdog Updater, Modified (yum) -
  Install, delete, update
• Manages RPM packages
  – Red Hat Package Manager - RPM Package Manager
  – A Linux distribution will commonly use either
  yum or apt-get

Question 12

Bash - ip

Answer 12

• Manage the network interfaces
  – Enable, disable, configure addresses,
  manage routes, ARP cache, etc.
• ip address
  – View interface addresses
• ip route
  – View the IP routing table
• sudo ip address add 192.168.121.241/24 dev eth0
  – Configure the IP address of an interface

Question 13

Bash - df

Answer 13

• Disk Free - View file systems and free space
• df
  – View number of blocks
• df -h
  – View human-readable sizes

Question 14

Bash - grep

Answer 14

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

Question 15

Bash - ps

Answer 15

• 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 16

Bash - top

Answer 16

• View CPU, RAM, and resource utilizations
  – The “Task Manager” for Linux
• Process information
  – Easy to find the highly utilized applications
• Summary of overall load
  – One, five, and fifteen minutes
• Many different options
  – Check the man page for startup options and keys

Question 17

Bash - find

Answer 17

• Find a file by name or extension
  – Search through any or all directories
• Find files with a specific extension
  > find . -name “*.txt”

Question 18

Bash - dig

Answer 18

• Lookup information from DNS servers
  – Canonical names, IP addresses, cache timers, etc.
• dig (Domain Information Groper)
  – Detailed domain information

Question 19

Bash - cat

Answer 19

• Concatenate - Link together in a series
• Copy a file/files to the screen
  cat file1.txt file2.txt
• Copy a file/files to another file
  cat file1.txt file2.txt > both.txt

Question 20

bash - nano

Answer 20

• Full-screen text editor - Easy to edit
• Included with many Linux distributions - Easy to install
• Select, mark, copy/cut, and paste text
  – Similar features to graphical-based editors