1. Press Ctrl + H and you will see the hidden files immediately. It is very useful short cut key but remember that when you restart your file browser all hidden files will disappear again.

2. If you want to make them visible by deffault, click Edit from your file browser toolbar and select Preferences. Then in the new window check the option Show hidden and backup files.

/bin - The bin directory contains the commands and utilities that are used most commonly in GNU/Linux like ls, cd, and rm. Since these are executable binary files, the directory is named bin for short.

/boot – The boot directory contains the Linux kernel, the bootloader configuration files, and all other files that the system needs in order to start up, or boot.

/dev -  This is where all of the device files for the system are stored. This directory is rather unique since the files are actually the hardware devices themselves and are treated just like files in that you can read and write them. The label /dev/sda (or /dev/hda) refers to the computer’s first hard drive. SCSI drives are labeled sda, while IDE drives are hda.

/etc – Pronounced “et-see,” this directory is home to all of the system-global configuration files for all system users. For example, /etc/passwd contains information that defines all of the user accounts, while /etc/init.d is home to the scripts that run when Ubuntu is booting up.

/home – Home is where the files are—the user’s files, that is. This is where documents, music, pictures, videos, and so on, are stored for the individual user. Its size depends on how many users will be using the system and what files are to be stored in their directories. Each user on a computer has his or her directory under /home.

/lib – Shared libraries and kernel modules are stored in this directory. The files here are similar to DLL files in Microsoft Windows.

/media – The media directory serves as the mount point for all external devices like CDs or DVDs. Devices mounted to the media directory are done automatically.

/mnt -  The mnt directory is home to temporarily mounted devices like a network shared folder. Mounts to the mnt directory are done manually as opposed to automatically as with the media directory.

/opt - The opt directory is used to store software that is not managed by the package manager. These are generally add-on software packages that the user downloads outside of the Ubuntu repositories.

/proc - The proc directory is actually a virtual directory that provides a means for the kernel to communicate with the processes running on the computer. Each process that is running is assigned a numbered entry, which we will learn more about shortly.

/sbin -  This directory contains files and commands like the bin directory does; however, the programs housed in sbin are only used in system administration tasks and require superuser privileges to run them. When you run something using the sudo command, odds are it comes from this directory.

/srv -  This directory is home to the data files used to run services like HTTP, FTP, or TELNET.

/sys – This is another virtual file system that was added for plug-and-play devices. It contains files showing the resources that are allocated to each device on the system.

/tmp -  The tmp directory stores temporary files. Nothing more, nothing less. Some applications — including archive manipulators, CD/DVD authoring tools, and multimedia software — may use /tmp to temporarily store image files.

/usr -  This is the directory that stores everything for the user’s applications such as dictionaries for spell checkers, documentation, and source code files. Subdirectories such as /usr/bin and /usr/lib contain all user programs, libraries and documentation.

/var – Files that change while the system is running are stored here. Log files, print spools, cache files, and anything else that would be considered a dynamic file would be found in the var directory. The size of this directory depends greatly on the usage of your system.

Note: There is a difference between the root directory, which is /, and a /root Note subdirectory. The / directory is the directory where everything branches out from. This is what we consider root. The /root subdirectory is the home folder for the root user.

Unless you are doing some configuring actions on your computer, you may never have to go into some of these directories; however, it is good to know what they are used for so that you don’t accidentally do anything to them or the files they contain while you are working in the shell.

That’s because Ubuntu comes without integrated support for CHM files since CHM is a proprietary format used by Microsoft. However, this can be fixed easily by installing  third party tools like GnoCHM.

GnoCHM enables you to view files encoded in the MS ITSS format. These files are most commonly known as Microsoft Html Help files, and usually have a .chm extension.

GnoCHM has the following features:

• Full text search – it is possible to quickly search for words in the CHM archive.
• Bookmarks – you can save your favorite pages in each file and easily jump to them later.
• It supports external CHM links – some CHM files contain hyperlinks to other CHM files. GnoCHM is able to search a list of directories in order to automatically find these targets.
• Configurable support for HTTP links. Some of the links in a CHM file are to web sites. GnoCHM can be configured to open a web browser when one of these links is clicked.
• Gnome2 integration. GnoCHM supports internationalisation,Drag-n-Drop, On-line help, applications registry, mime database and standard gnome command line parameters (where supported by PyGTK).
• You can view multiple files at the same time without having to start new instances of GnoCHM.
• It is possible to display the HTML source of the current displayed page.

To install GnoCHM go to Applications > Add/Remove…. and type gnochm in the search box. Then select it from the list below and click Apply changes. Now in the following window click Apply again to confirm the installation.

Wine is an application that allows computers using Unix-based operating systems to run Windows applications, not emulate them. The way this works is that Wine is an implementation of the Windows application programming interface (API). An application programming interface is actually the interface that allows one program, let’s say Microsoft Word, to communicate with another program, Microsoft Windows. When applications written for Microsoft Windows utilize a format that GNU/Linux operating systems can’t understand, it is due to the API. In other words when you start a Windows application Wine takes its instructions and modifies them into something that Ubuntu will understand. But let’s see how it works.

Firt of all you need to install Wine, if you haven’t already done so. All you have to do is go to Applications > Add/Remove…. and type ” Wine” in the search box. Now from the list check  “ Wine Windows Emulator ” and click the “Apply changes” button. Then in the new window click “Apply” and wait for the installation to complete.

Now that Wine is installed let’s see how it works.

As you probably know the default directory to install programs in Windows is “C:\Program Files“, which is also used by most program installers. That’s why Wine creates fake C:\ drive that contains the folders Windows and Program files like in a real Windows installation. This allows you to install applications into Wine in the same way you would in Windows. The installation process is simple. Just download the program you want and double click on the executable file. You may find that Wine allows you to  create icons on your desktop and in your app menu (if the installer provides such an option ). If so, you can start the applications by clicking on them.

For example I’ve tested Wine by  installing  Winamp 5.53 and it worked fine.  There were some bugs such as not working timer and broken playlist editor window which goes back to its orginal shape just by clicking the PL button. Of course these are things that do not affect the normal operation of the program.

Note that during the installation of Winamp you may receive a message saying:   “This application is trying to show an HTML page. Wine needs Gecko (Mozilla HTML engine) to be installed to show the page. Click install if you want Wine to automatically download and install Gecko.” If so, then just click the ” Install ” button.

Here is a screenshot of Winamp working on Ubuntu.

This will install a SAMBA server on your machine. SAMBA allows file and printer sharing between computers running Windows and computers running Linux. It sets up network shares for chosen Linux directories that appear to Windows users as normal Windows folders accessible via the network. Linux users can either mount the shared folders as part of their file system or use  SMB client program ( included with the Samba distribution ) to access the shares. More info about SAMBA here and here.

After the installation you need to restart your session and repeat the first step in the post.

Note that the shared folders will be available only for  users registered on the same computer. To provide access to unregistered users right click on the folder you want to share and select “Sharing Options” , then check the option “ Guest access ” and click ” Modify Share “.

Now go to any Windows machine on your local network and open  My Computer > My Network Places.

Read permission means  that if you have this permission, you can open the file or directory.

Write permission means you have editing capabilities. You can make and save changes to the file or directory.

Execute means that if the file is a program, it can be executed.

Before you change permissions, let’s first see what permissions are already set to a file or directory. Let’s begin by looking at the permissions of the files and subdirectories in a current directory. From the terminal,  use the following command:
ls   -l

The ls command lists the contents of directories. If no path is  given, it lists the files in the current directory. The -l option lets you display a variety of information ( including permissions, owner, size, modification time, etc.) about the files contained in the selected directory. For example if you want to see a detailed information about the files in your Home directory just type the following in the terminal:

ls -l /home

To understand how to read permissions, just look at the picture above. If you look at the left column of the figure, you will  see the following: drwxr-xr-x or something. Analyzing this information is simple; the “d” stands for directory. If this first character is replaced by a – (dash), then it is a file. A “l” means that it is a link to something else in the file system. Next to the “d“, you will see characters that you need to divide into three groups of three ( in our case the first group is rwx , the second is r-x and the third is also r-x ). The first group  contains rwx, which means read, write, and execute. This first group of permissions belongs to the owner of the file or directory. The second group is r–x. This group describes the permissions for the group owning the file. The group has permissions only for read and execute, but not to write. The final group of permissions belongs to all other users. They can also read and execute, but not write.

To change permissions on a file, you will need to use the chmod command with a few options besides rwx.  The following symbols identify the user or group of users  you want to change the permissions.

To designate the owner,  use a ” u “. For the group, use “ g ” and for all others, you have to use “ o “. For all users and groups, you need to use an “ a ” option.  To add permissions,  use ” + “, and to take permissions away use ” – “. Let’s see how it works.

Examples:

chmod a+r filename - allow read permissions to everyone.

chmod go-w filename - deny write permissions to the group and others.

chmod a+rwx filename - give full access to everyone.

chmod o-rw filename – deny read and write permissions to others.

Another easier way to change permissions is to use numbers that represent read, write, and execute. See the following list:

#    Permission

7 Full

6 Read and write

5 Read and execute

4 Read only

3 Write and execute

2 Write only

1 Execute only

0 None

A sample command would look like the following:

chmod 777  filename - allow everyone to read write and execute the file.

chmod 755  filename - gives the owner full access to the file , the group read and execute the file and the others also read and execute the file.

As you can see there are three digits in a command. The first digit refers to the owner permitions, the second to the group and the third refers to all other users. I think this method is easier  because here you don’t need to use the “+” and “-” symbols in order to add or remove permitions.

1. Open the terminal and type “ifconfig”

2. Find the interface you want to change the mac address. If you have more than one network adapter installed on your machine, they are usually numbered as “eth0″ ,” eth1″ and so on.

3. Run the following command:

ifconfig <interface> down hw ether < new mac address >

This command stops the selected interface and changes its mac address. Note that you have to be either logged as ROOT or type “sudo” before every command or you will receive ” Permission denied” as a result.

Then the command will looks like this:

sudo ifconfig <interface> down hw ether < new mac address> .

You will be asked for the root password.

4. Now turn on the interface with the command: ifconfig <interface> up

For example, the  above commands may look like:

ifconfig eth0 down hw ether 00:19:B9:7A:C9:A1

ifconfig eth0 up

The only disadvantage of the described method is that after restart of the computer your MAC address will change to its default value. If you want to make it permanent even after restart, you have to edit the /etc/network/interfaces file and add following line in the section containing the settings of the selected network adapter so that the MAC address to be set when the device is started.

hwaddress <interface> < New MAC address >


For example : hwaddress ether 00:19:B9:7A:C9:A1

Here is part of my /etc/network/interfaces file after being edited:

iface eth1 inet dhcp
hwaddress ether 00:19:B9:7A:C9:A1
address 192.168.1.3
netmask 255.255.255.0
gateway 192.168.1.1
wireless-essid cartoon_network

auto eth1