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by Lars Vogel

Training Books

Ubuntu Linux - Tips and Tricks in using Ubuntu

Lars Vogel

Version 3.3

21.07.2013

Revision History
Revision 0.1	19.02.2008	LarsVogel	Created
Revision 0.2 - 3.3	04.05.2009 - 21.07.2013	LarsVogel	bug fixes and enhancements

Ubuntu - Typical Tasks

This articles contains some information about handling a Ubuntu system.

Table of Contents

1. Ubuntu

2. Unity

2.1. Overview
2.2. Adding entries to the launcher
2.3. Useful shortcuts

3. Using the console

3.1. Editor
3.2. Find files
3.3. Calculate the size of a folder
3.4. Remove files
3.5. Processes
3.6. Change own

1. Ubuntu

Ubuntu Linux is a full fledged Linux system trailed for the desktop. Ubuntu builds a unique user interface and offers the users a solid choice of tools.

2. Unity

2.1. Overview

Unity is the default windows manager on Ubuntu. It introduced the launcher on the left side of Ubuntu and the Dash to start programs.
Press the Windows key to start the Dash. Here you can type in commands to open programs and files.

2.2. Adding entries to the launcher

To add new entries to the launcher you can create an .desktop file and drag file on the launcher. For example the following creates an entry to start Eclipse with different shortcuts for different workspaces.

[Desktop Entry]
Icon=application-x-executable
Name=eclipse
Type=Application
Exec=/home/vogella/Eclipse37/eclipse

X-Ayatana-Desktop-Shortcuts=Docu;vogella;business
 
[Docu Shortcut Group]
Name=Docu
Exec=/home/vogella/Eclipse37/eclipse -data /home/vogella/workspace/docu
TargetEnvironment=Unity

[vogella Shortcut Group]
Name=vogella
Exec=/home/vogella/Eclipse37/eclipse -data /home/vogella/workspace/vogella
TargetEnvironment=Unity

[business Shortcut Group]
Name=business
Exec=/home/vogella/Eclipse37/eclipse -data /home/vogella/workspace/business
TargetEnvironment=Unity

2.3. Useful shortcuts

The following lists a few useful shortcuts for the Unity window manager.

Table 1. Window Shortcuts

Long press on Super (Windows key)	Opens up help for the most common keyboard shortcuts
Alt+Left Mouse Click	Allows to moves the current window

3. Using the console

To open a console open the Dash and type in Terminal. Alternatively you can use the shortcut Ctrl+Alt+T. This will open a window which allow you to issue commands.

3.1. Editor

Ubuntu offers several editors which are installed by default. The most common command line editor is vim.
To install vim on your Ubuntu machine use the following command.

sudo apt-get install vim

Start vim from the command line. vim has two modes, one editing mode and other mode in which you can move within the file. To start editing the file use the "i" key. Once you want to save press the escape button and write ":wq". If you want to exit without saving use ":q!".
A simple editor with a graphical user interface is gedit.

3.2. Find files

The following demonstrates the usage of the find command.

Table 2.

Command	Description
find dir -name "pattern" 2>/dev/null	Finds recursive all files which apply to the pattern "pattern" starting from the directory "dir". The 2> Send all error messages to the null device.
find . -name '*.java' -newer build.xml -print	Search for all java files newer then the file build.xml
find . -name '*.java' -mtime +7 -print	Search for all java files newer then 7 dates
find . -name '*.java' -mtime +7 -print0 \| xargs -0 grep 'swt'	Search for all java files newer then 7 dates using "swt". The -0 options is used for files and folders with spaces.

The find command can also be combined with the grep command. See Using the grep command .

3.3. Calculate the size of a folder

The following calculates the size (disk usage))of a folder "folder1" in megabyte.

du -sh folder1

3.4. Remove files

Use the command "rm pattern"" to delete files. Be careful with the usage of files.

# Remove all files which ends with .class in the current directory
rm *.class
# find all files which ends with .class recursive in all directories below the current one and delete them
find . -type f -name "*.class" -exec rm -vf {} \;

3.5. Processes

To see all running processes on your system use

ps -aux

3.6. Change owner of files and directories

Table 3.

Command	Description
chown -R www-data:www-data mydir	Change recursively the owner and the group of the directory "mydir" and its subdirectories.

3.7. Creating links

You can create a softline to a file or directory for the following command.

# Create a new soft link via
# ln -s target link

# For example
ln -s ~/workspace/e4-dev e4tools

3.8. Zipping files

To zip or unzip files on the command line you can use the following comands.

# Zip all pdf files in the ~/tmp/pdf/ diretory
zip ~/targetdir/myzip.zip ~/tmp/pdf/*.pdf


# Unzip the zip file
unzip ~/targetdir/myzip.zip

4. User management

4.1. Creating new users

To create a new user via the console use the following commands. This will create the user, set his password and create a home directory for the user. The -m parameter is responsible for creating the home directory of the user.

# create user with home directory
sudo useradd -m -s /bin/bash newuser

# assign password to user
sudo passwd newuser

You can also create new user groups and assign the user to the new group with the following command.

sudo addgroup gerrit
sudo usermod -G gerrit newuser

4.2. Manually creating the home directory

In case you need to create the home directory at a later stage you can use the following command which creates the home directory and change this ownership of the directory.

# alternatively to using the -m option
# you could create the 
# home directory manually
# sudo mkdir /home/newuser
# sudo chown newuser /home/newuser
# sudo chgrp newuser /home/newuser

4.3. Giving root access

Careful: The following command allows the user to execute sudo commands (root).

# either this one
sudo adduser vogella admin

# or this one should work
sudo adduser vogella sudo

# afterwards to may want to lock 
# the root user 
# CAREFUL!!!

# sudo passwd -l root

To change the default shell of the user to bash set the last entry of the corresponding user in the /usr/passwd file to the /bin/bash following as in the following example.

testuser:x:1001:1001::/home/testuser:/bin/bash

5. Environment Variables

Table 4.

Command	Description
echo $VARIABLE	Prints the content of the environment variable
sudo /etc/init.d/tomcat5 start/stop	Start / stops the tomcat server
sudo -i	Switches to root

5.1. Add a directory to the path

The PATH environment variable is where the system will look for executable files. To temporary add the /home/vogella/bin directory to the PATH use the following command.

export PATH=$PATH:/home/vogella/bin

If you want to add a directory permanently to the path you can edit / create the file .bashrc and add the following line to the file. Every new directory in the path must start with :.

PATH=$PATH:path_to_new_directory

Open a new shell to make the changes in the .bashrc file active.

6. Important files

Table 5.

File	Description
/etc/issue	Contains the Ubuntu version you are running
lsb_release -a	Prints out the Ubuntu version you are running
/etc/apt/sources.list	Contains the available sources for software installation
/usr/share/tomcat	Installation directory for tomcat
/var/www/vhosts/domain1	Contains on my v-server the user directory for a specific domain which is hosted on this server

7. Package Management

On the command line Ubuntu allows to install / remove and search for packages via the following commands.

Table 6.

Command	Description
sudo apt-get install paketname	Installs a package
sudo apt-cache search openjdk	Search for all packages which contain openjdk. The found package can get installed via the "apt-get install" command.
aptitude purge	Removes a package and orphaned dependencies and its configuration files
sudo apt-get update	Update the local package list
sudo apt-get upgrade	Updates any installed packages for which an update is available. Will not install new packages or remove packages to satisfy dependencies.
sudo apt-get dist-upgrade	Install available updates for the Ubuntu release you already have installed. Also installs new packages or removes existing packages to satisfy dependencies.
aptitude clean	Deletes downloaded files which were necessary for installation
aptitude show	Show details about a package name
dpkg -L packagename	Lists all files and their location in a package
sudo updatedb; locate javac	Updates the installation database and locates the javac command.

To search for the installed packages use the following command.

cat /var/log/dpkg.log | grep "\ install\ "

8. ShellScript

Shell scripts are short programs that are written in a shell programming language and interpreted by a shell process in the console. You can create these programs via a text editor and execute them in a terminal window.
Create for example the following text file.

chmod 777 yourScript

You also have to make this file executable via:
Create for example the following text file "yourScript".

#!/bin/bash
clear
echo "Hello, world."

Now you can call the shell script via ./yourScript. It should print "Hello, world" to the console.

9. Network

9.1. See all open ports on your machine

You see all listeners on your machine via the following command. Port which listen to 127.0.0 cannot get accessed from external.

netstat -anltp | grep "LISTEN"

9.2. SSH access to the server

The ssh command provides secure, encrypted access to a server. Use ssh IP-address to access the server.
You can also assign a shortname for an IP address via the config file in your ~/.ssh director.
For example to create an alias called foo for the IP address 144.76.74.162 and to use the user called testing switch to your ~/.ssh directory, create the config file if it does not exists and enter the following.

host foo
hostname 144.76.74.161
user testing

To upload your public ssh key which allows you to login automatically into a server use the following command.

ssh-copy-id foo

9.3. Firewall

Ubuntu provides a uncomplicated firewall (ufw). To install it and only allow SSH, FTP, and webtraffic use the following command.

sudo apt-get install ufw
sudo ufw allow 80/tcp
sudo ufw allow 22/tcp
sudo ufw allow 443/tcp
sudo ufw allow 21/tcp
sudo ufw enable

9.4. Network commands

The following commands give you an overview of your network connections.

Table 7.

Command	Description
lspci -nn \| grep -i net
lsusb
iwconfig
ifconfig	Shows the network connections
lsmod
python -m SimpleHTTPServer	Start webserver serving current directory tree at http://localhost:8000/

9.5. Http debugging with curl

curl is a command line tool to issue and receive http (and other) request. For example if you want to see the HTTP output of a webpage use the following command.

curl http://www.vogella.com
// Or
curl -G http://www.vogella.com

If you want to the HTTPrequest header (including the HTTP status codes use the following command. This is for example nice to see if your server deliver a 404 return code for your self-defined error page.

curl -I http://www.vogella.com

You can set HTTP header information with the -h flag. For example to request a certain MIME type use the -H'Accept:MIME' option.

curl -I http://www.vogella.com -H'Accept:text/plain'

To use curl behind a proxy.

curl -x proxy:8080 -G http://www.vogella.com

Tip

curl is also available for Windows. Please see curl for Windows.

9.6. IRC

For IRC communication you can use the tool xchat. To install it use "sudo apt-get install xchat".

9.7. Ftp

For Ftp access you can install filezilla via sudo apt-get install filezilla or map the ftp access to a virtual device.
To map the device select your desktop. Select the file menu and the entry "Connect to server".

10. MySQL

For a description of MySQL and its installation in Ubuntu see MySQL - Tutorial

11. Apache Tomcat

11.1. Important Files

Table 8.

File	Description
/usr/share/tomcat5/	Installation directory of Tomcat
psa-webapps	Installation directory for webapps in a vhost environment
/usr/share/tomcat5/conf	Configuration Directory for Tomcat
/etc/default/tomcat5	Contains default settings for tomcat. Most important the used java version (jdk).
/var/log/tomcat5	Log files of tomcat

11.2. Important Commands

Table 9.

Command	Description
/etc/init.d/tomcat5 restart	Restart the tomcat webserver

12. PDF files

12.1. Command line tool pdftk

The "pdftk" command line tool allows to rework existing pdf files, e.g. extract pages or change the orientation of the pdf file.
You can install it via the following command.

sudo apt-get install pdftk

For example to extract pages from an pdf document you can use the "cat" option.

# Extract certain pages from a pdf document
# "dont_ask" will override existing files without warning 
pdftk Eclipse4book-20120429.pdf cat 25-27 87-91 95 output Eclipse4-Exercise.pdf dont_ask

12.2. Converting .odp file to pdf in batch

If you have LibreOffice installed you can convert .odp files on the command line to pdf files.

soffice --nologo --invisible -convert-to pdf -outdir ./pdf *.odp

13. Command line tools for adjusting images

ImageMagick allows to convert images in batch see ImageMagick Command line Options.
For example the following adjusts the DPI size of images to 300.

convert -units PixelsPerInch -density 300 input.png output.png

14. Connection

14.1. Telnet / ssh client for Windows

To connect to your Linux system via telnet or via ssh from windows you can use putty Putty download page

14.2. Switch to Console mode from Graphical User Interface

In case your Linux system is runnig under a graphical user interface (KDE, Gnome,...) and you need access to the console, use the Ctrl-Alt-F1 shortcut keys to switch to the first console. To switch back to Desktop mode, use the Ctrl-Alt-F7 shortcut keys.

15. Tips

15.1. Creating a bootable USB disk with unetbootin

The default program for creating a bootable USB disk is Startup Disk Creator. This crashes frequently during the creation of a boot disk. The program unetbootin is much more stable. You can install it via the following command and start it on the command line.

sudo apt-get install unetbootin

To open this type "Menu Manager" in the Dash. Choose "programming" in the left panel. Press "New item" button then. Choose name, command, icon
In the panel click and hold Alt to quick switch/launch apps.

15.2. Defining text snippets via Autokey

The autokey tools allows you to define text snippets which can be inserted into any application. You can for example define "br::" and it can be replaced with "Best regards, Lars".

15.3. Eclipse IDE configuration

See Eclipse and Ubuntu for an introduction into the configuration of the Eclipse IDE under Ubuntu.

16. Thank you

Please help me to support this article:

17. Links and Literature

http://www.hosteurope.de/faq/index.php?cpid=13918 Java 1.5 on Virtual Server (German), (Could not create the Java virtual machine.).
http://blixtra.org/blog/2006/07/14/setting-up-tomcat-5-on-ubuntu-606/ Setting up Tomcat and Java on Ubuntu