Ubuntu – Linux Useful Commands

Ubuntu – Linux
Useful commands
Editor: Nguyen Duc Minh Khoi
Email: ducminhkhoi@gmail.com
Website: http://nguyenducminhkhoi.blogspot.com
HCMC University of Technology @ Summer 2013
Main reference: Ubuntu Linux Toolbox by Christopher Negus François Caen

Forward
• This presentation just give you some basic commands to work with
Ubuntu – Linux environment, specially for non-developer users.
• If you want to look more information, search on the Internet with the
keyword: “Ubuntu x command” or “Ubuntu + function”
• Please refer to the main reference as much as possible you can
• If you have opportunity, you should buy the main reference book because
it explains clearly for you to understand.
• I just give you some examples taken from that book for you to easily
lookup as a reference book :D
8/2/2013 Ubuntu - Linux Commands 2

Contents
Starting Using Ubuntu
Working as a User
Working as an Administrator

STARTING USING UBUNTU
Section 1

Basic Linux Commands
• Every Linux Command have this format:
NameOfCommand (Options)* (Argument)*
– Options usually start with – or -- character
• Using help message:

man Command
• To find information about a command

Other useful commands
• Print main page descriptions that match keyword
• Using info documents

Managing Software with APT

Managing Software with APT (cont.)

Managing Software with aptitude

Managing Software with aptitude (cont.)

Important shortcuts with Shell
• Open shell on the new tab: Ctrl + Shift + t
• Open new terminal window: Ctrl + Shift + n
• Close tab with: Ctrl + Shift + w
• Highlight text and copy: Ctrl + Shift + c
• Paste it in shame or different window: Ctrl + Shift + v or click center
button on the mouse
• Full screen mode: F11
• Zoom in: Ctrl + Shift + +, zoom out: Ctrl + -
• Switch among tabs: Alt + 1, Alt + 2, Alt + 3 and so on
• Exit the shell: Ctrl + d
• Switch to another virtual console: Ctrl + Alt + F1, Ctrl + Alt + F2

History commands
• List entire history:
• Search for a string in history:

Redirect stdin and stdout

Redirect stdin and stdout (cont.)
• To append a file instead of overwrite it:
• Direct output stream to a special bucket file:
• Pipe with ls commands
• Pipe and redirection combine:

Using Alias
• List Alias that are currently set:
• Define your own alias for the current bash section:
• Remove an alias:
• Remember: Use tab key for suggestions

Other Useful Commands
• Acquiring Super User Power
• Using Environment Variable:
– Display all environment Variable:
– Set or reset variable yourself:
– Concatenate a string with existing variable:

Using regular files
• Regular files consist of data files (documents, music,
images, archives, and so on) and commands (binaries
and scripts)
• Use the file commands to see some file types:

Using regular files (cont.)
• Using directories

Setting File/Directory Permissions
• Changing permission with chmod

Setting File/Directory Permissions (cont.)

• Changing ownership
• The traversing the File System

Other useful commands (cont.)
• Copying files:
– -a: copying all files, retaining ownership and permission settings
• Finding files with locate

WORKING AS A USER
Section 2

Matching using regular expression

Editing text files with nano Editors
• Control keys for nano

Nano Editors (cont.)

Listing text file
• Output top 10 lines of a file
• View ends of a file

Searching for Text with grep
– $ grep francois myfile.txt #Show lines containing francois
• Recursive search
– $ grep -R VirtualHost /etc/httpd/conf*
• Find the exact lines
– $ grep -Rn VirtualHost /etc/httpd/conf*
• Ignore the case
– $ grep -i selinux /var/log/messages #Search file for
selinux (any case)
• Checking word count with wc
– $ wc /var/log/dmesg #List counts for a single file
436 3847 27984 /var/log/dmesg

• Sort output with sort
– $ dpkg-query -l | grep kernel | sort #Sort in alphanumeric
order
– $ dpkg-query -l | grep kernel | sort -r #Sort in reverse
alphanumeric order
• Replacing text with sed
– $ cat myfile.txt | sed s/francois/chris/
– $ sed s/francois/chris/g < myfile.txt > mynewfile.txt
• Checking different between 2 files:
– $ diff config config.old

Working with audio
• Install sox:
• Using play command:

Working with audio (cont.)
• Using ogg123 to play ogg file (install ogg123 package first)
• Using mpg321 to play mp3 file (install mpg321 package first)

Working with audio (cont.)
• Convert audio files
• Display info about a file
• Delete seconds of sound

Working with Images
• Install ImageMagick package: $ apt-get install imagemagick
• Getting info about images:
• Converting images:
• Resize image:

Working with Images (cont.)
• Rotate images:
• Add text to images:
• Creating thumbnails:
• Making image fun and weird:

Browse the Web
• Use elinks package to view

Transferring files
• Download file with wget:
• FTP server requires login and password:
• Download a single webpage

Transferring files (cont.)
• Connect to a FTP server with lftp:

Copying remote files with scp

Chatting with friends in IRC
• Install IRC package:
• Connect to freenode server:
• Joining the centos IRC channel:

Configuring SSH
• Install OpenSSH:
• Logging remote with ssh:
• Accessing ssh on different port:

Mastering time
• Your computer running Linux keeps time in two different
ways:
– a system clock (which Linux uses to keep track of time)
– a hardware clock (that sets the system time when Linux boots up).
• Change current time zone:
• Change system date and time

Mastering time (cont.)
• Displaying and Setting on your system clock

• Display dates by month

• View the current time from hardware clock:
• Reset your system clock:
• Set hardware clock from system clock:
• Using network time:

WORKING AS AN ADMINISTRATOR
Section 3

File system basics
• The ext3 file system type is based on the ext2 file system type, adding a
feature called journaling to its predecessor.
• Journaling can improve data integrity and recovery, especially after
unclean system shutdowns.
• Time-consuming file system checks are avoided during the next reboot
after an unclean shutdown, because the changes that occurred since the
most recent write to disk are saved and ready to be restored.

Work with partitions
• Work with specific disk:
• Copying partition tables with sfdisk:
• Creating and using swap partition:

Listing Active Process
• Use ps and top commands

Listing Active Process (cont.)
• Custom view Processes:

Watching active Process with top

Finding and Controlling Processes
• Using grep:
• Using fuser

Changing Running Process
• Adjust process priority with nice
– nice value that can be used to tell the Linux process scheduler what priority
should be given to that process.
– The default nice value is 0. You can use the nice command to run a process at
a higher or lower priority than the default. The priority number can range
from –20 (most favorable scheduling priority) to 19 (least favorable scheduling
priority).
– Although the root user can raise or lower any user’s nice value, a regular user
can only lower the priorities of a process (setting a higher nice value).
– See current nice value
– Changing nice value:

Changing Running Process (cont.)
• Changing process nice value:
• Running process in background and foreground

Changing Running Process (cont.)
• Manage background jobs:
• Kill process:

Monitoring Resources
• First install sysstat package:
• See how much memory is being used

Monitoring Resources (cont.)
• View memory used over a give period:
• View info about processor itself

Monitoring Resources (cont.)
• List info about disk reads and writes

Managing network interface card
• Use ethtool command:

Managing network interface card (cont.)

Ethernet connection
• Show address info and status of eth0 Ethernet interface:
• Get information both active and inactive NICs

Ethernet connection (cont.)
• See info on all interfaces:

Troubleshooting network problems
• Make sure there is IP - connectivity to that gateway

Troubleshooting network problems (cont.)
• Check your default gateway:
• Tracing route to host:

Display netstat connections

Working with user and groups
• Adding user accounts:
• Create new users with home directory: /home/willz
• Add password:

Working with user and groups (cont.)

Modifying User account

Modifying User account (cont.)

Managing passwords

Working with groups
• Getting info about user log on system:

Checking on Users

THANKS FOR WATCHING
Khoi Nguyen (ducminhkhoi@gmail.com) @ HCMUT 2013

Ubuntu – Linux Useful Commands

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