I have a Drobo, basically a consumer grade NAS or network file share device, that I store the majority of my media and documents on. The files are accessed via an exposed Windows share folder and because Linux doesn’t always play the nicest with that I’ve taken to force mounting these shares on my machine via fstab. The usual approach is to add something like this to your /etc/fstab file:
//{IP address of server}/Media /media/Drobo/Media cifs guest,uid=1000,iocharset=utf8 0 0
I won’t get into all of the gory details here (for that see this older post) but essentially this tells the computer to map the shared Media folder on my Drobo to a location on my computer under /media/Drobo/Media. The problem with this approach is that if the Drobo is offline or if there is a network problem then it will cause the boot process to pause with an error and prompt me if I want to continue without mounting it. While this is fine it isn’t always ideal. For instance what if I wanted to do something similar with my laptop but not have to go through the hassle of OKing the boot every time it failed to find the Drobo when I’m away from home? Well thankfully there are a few more switches we can add to the fstab line to do just that!
Here is what my new fstab line looks like:
//{IP address of server}/Media /media/Drobo/Media cifs nofail,x-systemd.automount,x-systemd.requires=network-online.target,x-systemd.device-timeout=10,guest,uid=1000,iocharset=utf8 0 0
I’ve bolded the new portion but it should be fairly obvious what is happening here. Basically the nofail option says “I don’t care if you can’t mount it, don’t stop with an error just keep going” where the other options specify requirements to even try such as network connectivity as well as a timeout value so I don’t have to wait long for it to realize that it can’t find the Drobo. With these added options I can easily boot with or without the Drobo being there and I’m never prompted with an error message.
Now a few things to note:
Adding nofail to devices you do need to mount, such as your root drive, is probably a terrible idea.
If the computer boots up when the Drobo isn’t there but later I bring the computer back to the network where the Drobo lives, it won’t automatically find and mount it for me. So that’s something you’ll still need to remember to do manually (by running sudo mount -a or something like that).
In the previous posts, we talked about some of the basic Linux commands, today we continue our journey, and we will talk about something very important in Linux which is Linux Environment Variables.
So what are Environment Variables and what is the benefit of knowing them?
Well, the bash shell uses a feature called Environment Variables to store some values which are required by the running programs or scripts from that shell, actually, this is a very handy way to store data and make it available for any script or a program when you run it from the shell.
There are two types of environment variables in the bash shell:
Global variables
Local variables
Global variables are visible from the shell session and for any running process that runs from the shell.
Local variables are visible in the shell that creates them.
Global variables
The Linux system sets some global environment variables when you log into your system and they are always CAPITAL LETTERS to differentiate them from user-defined environment variables.
To see these global variables, type printenv command:
As you can see, there are a lot of global environment variables, to print only one of them, type echo command followed by $VariableName. Ex: to print HOME variable type echo $HOME.
Local variables
Actually, the Linux system also defines some standard local environment variables for you by default.
Unfortunately, there is no command that displays only local environment variables, but if you type the set command, you will see the global and local variables for the shell you are running and available to that shell.
Setting Local Environment Variables
You can set your own environment variables directly from the shell, once you open the shell you’re allowed to create local variables that are visible within your shell process. You just type variableName you want, followed by an equal sign and the variable value.
You just type variableName you want, followed by an equal sign and the variable value WITHOUT any spaces:
mysite=likegeeks
And to print the variable value, use the echo command:
echo$mysite
Sure enough, it prints likegeeks.
OK, what if your variable is more than one word; may be a long string, you can put the string between single quotations:
mysite=’likegeeks is a website that offers tech tutorials for geeks’
And if we type echo$mysite
If you forget the single quotation, the shell will assume that the second word is another command and will give you an error.
As you can see, I use lower case characters for my variable not upper case and this is recommended NOT required, this helps you distinguishing your environment variables from the system environment variables.
Once you have set your local variable, it will be visible in the currently running shell scope and that means if you start another shell window the variable will not be available in that new window.
Setting Global Environment Variables
To create a global environment variable, you have to create a local environment variable then export it to the global environment like this:
myvar=’I will do it likegeeks’
echo $myvar
export myvar
As you can see I don’t use dollar sign with the export command so make sure of that.
But there is something, when I close the shell and open it again the variable is gone, so how to make it persistent?
Persisting Environment Variables
Just edit $HOME/.bashrc and type export myvar=‘welcome to likegeeks’ and save the file:
Removing Environment Variables
This can be done by using the unset command:
Default Shell Environment Variables
As we know, the system defines some variables for us, one of those variables is the PATH variable, this variable holds the paths of the directories that the shell uses to look for commands, each directory is separated by a colon.
Setting the PATH Environment Variable
If you to add a directory to the PATH variable, the shell will search in that directory also for an executable to run when you type any command.
Just append the path variable followed by a colon and the new directory like this:
And if you want to persist the PATH variable, you have to edit the .bashrc file and add type it like this:
There is a useful trick that some sysadmins do which is adding a period . to the path variable so the shell will search for an executable in the current directory you are in wherever you are.
This is relatively risky, you might give the attacker the opportunity to run a malicious script or malware in his current directory, so if you do this trick, you should know what you are doing.
Locating System Environment Variables
There are three ways of starting a bash shell:
default login shell at login time
the interactive shell that is not the login shell
non-interactive shell to run a script
login shell
When you log into the Linux system, the bash shell starts as a login shell. The login shell looks.
There are four startup files that you can process the commands from:
/etc/profile
$HOME/.bash_profile
$HOME/.bash_login
$HOME/.profile
/etc/profile runs on every startup with every user, the other 3 files run for every specific user, you can call them user specific environment variables.
Interactive shell
If you start a bash shell without logging into a system like when you go to the rescue mode, this is the interactive shell.
If you start an Interactive shell, the system will not look for /etc/profile but instead will look for .bashrc in your HOME directory.
Non-interactive shell
This shell starts by the system to execute a shell script.
Users can customize the above-mentioned files to include environment variables and startup scripts for their own use, just edit the desired file and type the variable you want and save it.
Variable Arrays
One of the cool features of environment variables is that they can be used as arrays which hold multiple values.
myvar=(first second third fourth)
Now if you check the value of that array using echo command, you will find it returns the first element only.
To get a specific element, just reference it by its position, and the positions start from zero so to get the third one, type it like this:
echo${myvar[2]}
To display the entire array type asterisk instead of a number:
echo${mytest[*]}
You can remove an element of the array using unset command:
In the previous post, we discussed some Linux commands and we saw how to show files, traverse directories, make them, and much more. Now, that was just the first level of the basic Linux commands. Let’s take one more step and see more of the basic Linux commands that you will use.
We talked about the ls command in the previous post and we’ve discussed only 2 parameters. Let’s dig deeper and see more parameters that can make you more powerful.
ls–R to recursively list all files in a directory
The -R parameter will traverse deeply till it finishes all directories. As you can see, for large directory structures, this can become quite a large output listing.
ls–r Reverses the sorting order for the displayed files and directories.
ls–S Sorts the output by file size.
ls–t Sorts the output by file modification time.
Filtering Output
ls–lmyfile?
A question mark is used to represent one character.
ls–lmyprob*
An asterisk is used to represent zero or more characters.
The question mark and asterisk are called wild characters.
Creating Files
touchtest1
The touch command is used to create an empty file. You can use the touch command to change the access and modification times of an existing file without changing the file contents.
If you use it against an existing file, it will change the access time, if the file doesn’t exist, it will create it.
In order to change the modification time, just type it with -t followed by the time with the following format YYYYMMDDHHMM
touch–t202012011200test1
Linking files
We know from the previous post that cp command is used to copy files.
What about creating a shortcut to that file in a different place. In Linux, this is called linking files.
There are two different types of file links in Linux:
hard link
symbolic, or soft link
cp–lfile1 file2
Hard Links
The hard link creates a separate file which contains information about the original file and where it is located.
Keep in mind that you can only create a hard link between files on the same physical drive, you can’t create hard links between files under separate mount points.
If you need to create links on a different physical drive, you’ll have to create a soft link instead.
Symbolic Links
The -s parameter creates a symbolic or soft link:
cp–sfile1 file2
Here we should mention also another command that makes links other than cp which is ln command, you can create hard and soft links with it like this:
lnmyfile myfile2
This command creates a hard link.
ln–smyfile myfile2
This command creates a soft link.
Viewing the file type
file myfile
Determines the kind of the file.
Viewing parts of a file
We know also from the previous post the cat command and the less command. Another important command that you will use a lot in your daily work which is the tail command.
The tail command
This command displays the last 10 lines of a file.
-n parameter to specify the number of lines
-f parameter to stay on the file and continue to watch the last lines you specified like monitoring, and this is very important when looking at log files.
The head command
Like tail command, but this command displays the first 10 rows of a file with the same tail command parameters.
Running Processes
psaux
This command is to see the currently running processes.
top command shows the running processes.
-c parameter to show the command path that is running.
kill command to kill a running process.
To kill a process
pkill processName
type xkill and press Enter to kill any nonresponsive window.
df command shows the disk free space.
df–h
-h for human readable value
That was some of the basic Linux Commands. I hope you enjoy it. Keep coming back.
In my previous post I mentioned that I installed Zorin OS onto an older laptop I had lying around.
Very nice first impression
Since that post went up I have been messing around with Zorin OS and decided to run a system update to make sure I had the latest packages and security fixes installed. Unfortunately after the update finished and I rebooted I logged in to find that things just weren’t what they used to be… Instead of the nice Zorin OS interface (shown above) I ended up logging in to a standard GNOME Shell interface. It seems as though the update had reset some of the customization that the Zorin team had made.
Thankfully I was able to find the Tweak tool and re-enable many of those customizations again!
Once I enabled all of the Zorin OS extensions almost everything was back to normal!
The one thing that I couldn’t get back to normal was the duplicate top bar showing open applications. You can see it in the screenshot above but basically I now had both the Zorin OS styled open window bar at the bottom as well as the GNOME Shell version at the top.
The solution it turns out is to turn off all of the Zorin OS extensions that I had tried in the tweak tool and instead open up the Zorin Appearance tool and select the first of the three window options at the top.
Both the first or second selections should work
The last key to the puzzle was to log out and then log back in for everything to take. And now my desktop is back to normal again!
In the previous post, we discussed how to install Linux, now we are going to talk about the most powerful features in Linux which is Linux commands or shell commands.
For the whole documentation of Linux Commands, you can check Linux Documentation.
If you will use Linux, you should know that the power of Linux resides in its shell and the commands that you can use on that shell which gives you the ultimate power.
I’m going to talk about the main Linux commands with their main parameters that you might use daily.
ls Command
List the content of the current directory.
Parameters
–l
to list the content as a detailed list.
-a
Display all files includes hidden files.
You can combine parameters like this:
ls–la
cd Command
Change directory from the current directory to another one.
cd/home
Will go to home directory
cp Command
Copy the source to target.
Parameters
-i
Interactive mode means wait for the confirmation if there are files on the target will be overwritten.
-r
Recursive copy means include subdirectories if they found.
Example
cp –ir sourcedir targetdir
mv Command
Move the source to target and remove the source.
Parameters
-i
Interactive mode means wait for the confirmation if there are files on the target will be overwritten.
Example
mv –isourceFile targetFile
rm Command
Delete file or directory and you must use –r in case you want to delete a directory.
Parameters
-r
Recursive delete means delete all subdirectories if found.
-i
Interactive means wait till confirmation
mkdir Command
Create new directory
mkdirnewDir
rmdir Command
Delete a directory
chown Command
Change the ownership of a file or directory to the user you specify.
Parameters
-R
Capital R here means to change ownership of all subdirectories if found and you must use this parameter if you use the command against a directory.
chown –Rroot:root myDir
chmod Command
Change the permission of a file or directory.
Parameters
The mode which is divided into 3 parts, owner, group, and others means what will be the permissions for these modes, and you must specify them.
Every one of the 3 modes takes a permission.
The permission is one of the followings:
Read =4
Write = 2
Execute =1
Every permission represented by a number as shown and you can combine permissions.
Example
chmod755myfile
That means set permission for the file named myfile as follows:
owner: set it to 7 which means 4+2+1 means read+write+execute.
group: set it to 5 which means 4+1 means read+execute.
other: set it to 5 which means 4+1 means read+execute.
Note: execute for a folder permission means opening it.
locate Command
To find a file in your system, the locate command will search the system for the pattern you provide.
locate myfile
updatedb Command
updates the database used by the locate command.
date Command
Simply prints today’s date. Just type date on the shell.
tar Command
Combines several files into archive and compression if you want.
Parameters
-c
Create new archive.
-z
Compress the resulting archive using gzip package.
-j
Compress the resulting archive using bzip2 package.
-v
Verbose mode show the processed files.
-f
Write the output to a file and not to screen.
-x
Unpack files from archive.
Example
tar –czvf myfiles.tar.gzmyfiles
This command will pack and compress all files in folder myfiles to a compressed archive named myfiles.tar.gz.
tar–xzvf myfiels.tar.gz
This command will decompress the archive.
cat Command
Display file content to screen without limits.
Example
catmyfile.txt
less Command
Displays file content with scroll screen so you can navigate between pages using PgUp, PgDn, Home, and End.
less myfile
grep Command
Searches for a string in the specified files and displays which line contains the matched string.
Parameters
-R
Recursive search inside subdirectories if found.
-i
Insensitive search and ignore case.
-l
Display file name, not the text lines.
Example
grep –Ril mystring/home
passwd Command
Used to change your user password.
du Command
Calculates the disk usage of a file or a directory.
Parameters
-h
Display human readable form.
-s
Summarize the output total size.
Example
du –hs/home
reboot Command
Reboot the system immediately. Just type reboot.
halt Command
Shuts down the system, but make sure to close all of your files to avoid data loss.
That was just some of the main Linux commands.
Notice that, if you forget any command parameters, just type the command with – -help as a parameter and it will list the used parameters so you don’t have to remember all those parameters at the beginning.
As we’ve talked about Linux on the previous post and we have chosen the best Linux distro already and also we learn how to install Linux not it is the time to dig down and understand Linux from inside and we will start with what we’ve mentioned on load post which is what is the Linux file system.
If we want to talk about Linux File System we need to talk about it from download level and top level in order to fully understand it
You can check this link for a general overview File System
Down Level Explanation
Linux File System or any other file system is the layer which is under the operating system that handles the positioning of your data on the storage without it the system cannot know which file starts from where and ends where.
We talk about Linux, which supports many filesystems windows. MacOS and many other file systems, you can even download software that can handle a new file system when it comes and deal with it
Linux File System Types
So what are Linux file system types?
When you try to install Linux you will see that in order to install Linux you have to install it on a partition or a disk that is one of the following file systems
Ext, Ext2, Ext3, Ext4, JFS, XFS, btrfs and swap
So what are those file systems that Linux use?
Ext: old one and no longer used due to limitations
Ext2: first Linux file system that allows 2 terabytes of data allowed
Ext3: came from Ext2, but with upgrades. It keeps the backward compatibility and you can upgrade your Ext2 to Ext3 without problems
The only problem about it that the servers use this kind of file system because this file system does not support file recovery or disk snapshots
Ext4: faster and allow large files with significant speed
It is a very good option for SSD disks and you notice when you try to install any Linux distro it is the default file system that Linux suggests
JFS: old file system made by IBM it has a Good performance for both large and small files and because of its low CPU usage but failed and files corrupted after long time use reports says
XFS: old file system which shows a bad performance with small files and you can’t compare it with Ext versions rich features
Btrfs: made by oracle it is not stable as Ext in some distros but you can say that it is a replacement for it if you have to, it has a good performance
You may notice From the comparison above that Ext4 is the best Linux File System
Top Level Explanation
Now you know what file system Linux offers you ok what is inside that system and what is the system structure
You may come from windows background and windows has partitions like C:\ and D:\ and folders and you install the windows on any of those partitions usually C:\
What about Linux File System Hierarchy well it has a different structure than windows. If you navigate to the root partition which is / and see the structure of the Linux File System. Most distros have the same structures like this:
Linux File System Directories
/bin: Where Linux core commands reside like ls, mv
/boot: Where boot loader and boot files are located.
/dev: Where all physical drives are mounted like USBs DVDs.
/etc: Contains configurations for the installed packages.
/home: Where every user will have a personal folder to put his folders with his name like /home/likegeeks.
/lib: Where the libraries of the installed packages located since libraries shared among all packages. Unlike windows, you may find duplicates in different folders.
/media: Here is the external devices like DVDs and USB sticks are mounted and you can access their files from here.
/mnt: Where you mount other things Network locations and some distros you may find your mounted USB or DVD.
/opt: Some optional packages are located here and this is managed by the package manager.
/proc: Because everything on Linux is a file, this folder for processes running on the system and you can access them and see much info about the current processes.
/root: The home folder for the user root.
/sbin: Like /bin but here binaries for root user only.
/tmp: Contains the temporary files are located.
/usr: Where the utilities and files shared between users on Linux.
/var: Where variable data is located, like system logs.
Now you should understand what the Linux file system is.
Different file system lead to different performance so it is very important to know the file system at least a bit
Linux – The open-source OS we’ve all come to use and love and then use some more. I’ve been using Linux since 2009 at least and I have got to say, it’s capabilities have always managed to one-up my expectations. This is one operating system where I learn something new every other day. Across the years I’ve used various builds of Red Hat, Fedora, Ubuntu, Xubuntu, Mint, Debian and many more and I’m still not through. In fact, my love for Linux gets stronger with each day.
“It’s Not Meant For Entertainment”
Or so they say. Keeping Linux’s technical superiority aside, one of the most common criticisms directed towards Linux is its lack of compatibility with third party software. The general belief of an average user like me that is Linux is an absolute fit for developers and programmers but lacks that entertainment aspect for a normal user.
If it were 2012 when I was still struggling with it, I would have agreed. Not today though. The criticism is not really applicable anymore because today, Linux also supports one of the best free and open-source media player, Kodi.
“So, What is Kodi?”
Kodi is an impressive free multi platform media player that has also emerged as a great resource to watch films and TV for free. Kodi was introduced on Xbox as the Xbox Media Center (or XBMC), but that didn’t last for much long and now, the software exists in more than 65 languages, over a great number of platforms, and blending the work of hundreds of programmers.
Kodi as a free open-source media player plays all sorts of digital media comprising of TV (live and recorded), films, other videos, music, podcasts, photos, and slideshows. It’s also highly regarded for watching free ‘pirated’ copyrighted content.
“Is It Compatible With Linux?”
The Kodi application is available on multiple operating systems and hardware platforms such as Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user interface for use with televisions and remote controls. It allows users to play and view most videos, music, podcasts, and other digital media files from local and network storage media and the internet.
How to install Kodi on Linux
Installing Kodi on Linux is a piece of cake. Just add the PPA to your system, update the local repository index and install the Kodi package:
$ sudo add-apt-repository ppa:team-xbmc/ppa
$ sudo apt-get update
$ sudo apt-get install kodi
Or, use the below command to install audio codecs and other addons as well:
$ sudo apt-get install –install-suggests kodi
Optional, to remove kodi, do:
$ sudo apt-get remove kodi*
These installation instructions support Ubuntu 16.10 Yakkety Yak, Ubuntu 16.04 Xenial Xerus, Ubuntu 14.04 Trusty Tahr, Linux Mint 18.x, Linux Mint 17.x, Elementary OS 0.3 Freya and other Ubuntu derivative systems.
Moreover Kodi permits you to install third-party plugins that may grant access to free content available on the official content provider website. Team Kodi does not endorse the usage of illegal or pirated content which would otherwise need to be paid.
“One More Thing”
Since listening and watching pirated content can constitute trouble for the user it is recommended to employ a VPN which would hide your activities from the concerned authorities. Your online freedom is important. Stay out of the radar of data snoopers and online spies with the best VPN for Kodi. You are as vulnerable in the digital world as you are in the real world. Use a VPN to stay secure & safe online.
Despite the piracy linked criticisms, Kodi media player has established itself as a very popular application. Version 17 of Kodi has been released recently and is now available to be installed on Linux computers.
Brad is a tech blogger fascinated by technology, gadgets, latest developments the geek culture. Much as he loves writing about technological innovations and IoT, when he’s not, he can found playing games on his Xbox or hanging out with his beloved pets.
and hope you choose the one that is suitable for you
If you want to install Linux there are 2 ways to do that
First way is to download the Linux distribution you want and burn it to a DVD or USB stick and boot your machine with it and complete the installation process
The second way is to install it virtually on a virtual machine like VirtualBox or VMware and continue working on your windows or mac system without rebooting so your Linux system will be contained in a window you can minimize it and continue working on your system.
For me I prefer VirtualBox it’s a free and runs fast on my PC than VMware and natively support installing windows Linux mac OS with all versions
Let’s choose any Linux distro and install it using both 2 ways
Ok I’m going to choose Linux mint they call it the mac os of Linux
It is good distro for laptops and desktops for personal use
The version we are going to install is 18.1 “Serena” at the time of writing that article.
I prefer Cinnamon desktop version it is promising and elegant
Once you download the iso file you will have to burn it on DVD or the easy way copying it on USB stick using a program called universal USB installer from that link
After downloading the program open it and choose from the list the distro you want to install in our case Linux mint and make sure you put your memory stick on the computer and click next and wait till copying process is finished.
how to install Linux using USB
Now Finally we click create to create bootable USB
And now you can boot with this memory stick
Then Restart you PC and go to BIOS settings and select boot options and make sure the USB is the first one then it will show the installation screen press Enter it will load the live CD content which is on the USB or DVD
Then desktop will appear like that
Click install Linux mint
Then choose the language used for installation
Then choose the installation type and TAKE CARE if you are installing Linux on a disk that contains another system you MUST choose the option called something else
But if you installing it on new disk choose the option Erase disk
Linux requires 2 partitions to work on root partition and swap partition
Now we will create them by clicking the plus button and choose about 12 GB or more as you need but not less than that for root partition and choose mount type as / which stands for root and of course format will be Ext4
Now we create swap partition choose the remaining free space and click the plus button and choose swap area as shown
Then Create swap area
Then click install now and agree about writing changes to disk
Now you choose the time zone and click continue the choose the language
Now you write your username and password and click continue
Finally, installation started
After finishing installation it will prompt you to reboot the machine and remove the installation media DVD or USB
And yes this is how to install Linux on Physical machine
The second way it to install Linux is to install it on VirtualBox First download VirtualBox from here
The first way is easy it like the normal installation process
Open VirtualBox and click new and choose Linux and ubuntu 64
Then choose the RAM required not less than 1 GB and choose the disk file type or leave it as VDI and dynamically allocated and the size not less than 12 GB and hit ok
Then file location for disk to be used
So now the VirtualBox is created we just need to make it boot from the DVD we’ve downloaded
Choose from settings > Storage and choose the iso image and click ok.
Then choose the iso imageThen Click start
After loading the desktop click install Linux mint and the rest of the steps are as the mentioned above without any change And this is how to install Linux on a virtual machine.
This post was originally published on December 8, 2010. The original can be found here.
Note that while you can still write GTK+ applications on Linux using Objective-C as outlined in this post you may want to check out my little project CoreGTK which makes the whole experience a lot nicer 🙂
As sort of follow-up-in-spirit to my older post I decided to share a really straight forward way to use Objective-C to build GTK+ applications.
Objective-what?
Objective-C is an improvement to the iconic C programming language that remains backwards compatible while adding many new and interesting features. Chief among these additions is syntax for real objects (and thus object-oriented programming). Popularized by NeXT and eventually Apple, Objective-C is most commonly seen in development for Apple OSX and iOS based platforms. It ships with or without a large standard library (sometimes referred to as the Foundation Kit library) that makes it very easy for developers to quickly create fast and efficient programs. The result is a language that compiles down to binary, requires no virtual machines (just a runtime library), and achieves performance comparable to C and C++.
Marrying Objective-C with GTK+
Normally when writing a GTK+ application the language (or a library) will supply you with bindings that let you create GUIs in a way native to that language. So for instance in C++ you would create GTK+ objects, whereas in C you would create structures or ask functions for pointers back to the objects. Unfortunately while there used to exist a couple of different Objective-C bindings for GTK+, all of them are quite out of date. So instead we are going to rely on the fact that Objective-C is backwards compatible with C to get our program to work.
What you need to start
I’m going to assume that Ubuntu will be our operating system for development. To ensure that we have what we need to compile the programs, just install the following packages:
gnustep-core-devel
libgtk2.0-dev
As you can see from the list above we will be using GNUstep as our Objective-C library of choice.
Setting it all up
In order to make this work we will be creating two Objective-C classes, one that will house our GTK+ window and another that will actually start our program. I’m going to call my GTK+ object MainWindow and create the two necessary files: MainWindow.h and MainWindow.m. Finally I will create a main.m that will start the program and clean it up after it is done.
Let me apologize here for the poor code formatting; apparently WordPress likes to destroy whatever I try and do to make it better. If you want properly indented code please see the download link below.
//A pointer to this object (set on init) so C functions can call
//Objective-C functions
id myMainWindow;
/*
* This class is responsible for initializing the GTK render loop
* as well as setting up the GUI for the user. It also handles all GTK
* callbacks for the winMain GtkWindow.
*/
@interface MainWindow : NSObject
{
//The main GtkWindow
GtkWidget *winMain;
GtkWidget *button;
}
/*
* Constructs the object and initializes GTK and the GUI for the
* application.
*
* *********************************************************************
* Input
* *********************************************************************
* argc (int *): A pointer to the arg count variable that was passed
* in at the application start. It will be returned
* with the count of the modified argv array.
* argv (char *[]): A pointer to the argument array that was passed in
* at the application start. It will be returned with
* the GTK arguments removed.
*
* *********************************************************************
* Returns
* *********************************************************************
* MainWindow (id): The constructed object or nil
* arc (int *): The modified input int as described above
* argv (char *[]): The modified input array modified as described above
*/
-(id)initWithArgCount:(int *)argc andArgVals:(char *[])argv;
/*
* Frees the Gtk widgets that we have control over
*/
-(void)destroyWidget;
/*
* Starts and hands off execution to the GTK main loop
*/
-(void)startGtkMainLoop;
/*
* Example Objective-C function that prints some output
*/
-(void)printSomething;
/*
********************************************************
* C callback functions
********************************************************
*/
/*
* Called when the user closes the window
*/
void on_MainWindow_destroy(GtkObject *object, gpointer user_data);
/*
* Called when the user presses the button
*/
void on_btnPushMe_clicked(GtkObject *object, gpointer user_data);
@end
MainWindow.m
For the class’ actual code file fill it in as show below. This class will create a GTK+ window with a single button and will react to both the user pressing the button, and closing the window.
-(void)printSomething{
NSLog(@”Printed from Objective-C’s NSLog function.”);
printf(“Also printed from standard printf function.\n”);
}
-(void)destroyWidget{
myMainWindow = NULL;
if(GTK_IS_WIDGET (button))
{
//clean up the button
gtk_widget_destroy(button);
}
if(GTK_IS_WIDGET (winMain))
{
//clean up the main window
gtk_widget_destroy(winMain);
}
}
-(void)dealloc{
[self destroyWidget];
[super dealloc];
}
void on_MainWindow_destroy(GtkObject *object, gpointer user_data)
{
//exit the main loop
gtk_main_quit();
}
void on_btnPushMe_clicked(GtkObject *object, gpointer user_data)
{
printf(“Button was clicked\n”);
//call Objective-C function from C function using global object pointer
[myMainWindow printSomething];
}
@end
main.m
To finish I will write a main file and function that creates the MainWindow object and eventually cleans it up. Objective-C (1.0) does not support automatic garbage collection so it is important that we don’t forget to clean up after ourselves.
//create an AutoreleasePool
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
//init gtk engine
gtk_init(&argc, &argv);
//set up GUI
MainWindow *mainWindow = [[MainWindow alloc] initWithArgCount:&argc andArgVals:argv];
//begin the GTK loop
[mainWindow startGtkMainLoop];
//free the GUI
[mainWindow release];
//drain the pool
[pool release];
//exit application
return 0;
}
Compiling it all together
Use the following command to compile the program. This will automatically include all.m files in the current directory so be careful when and where you run this.
Once complete you will notice a new executable in the directory called myprogram. Start this program and you will see our GTK+ window in action.
If you run it from the command line you can see the output that we coded when the button is pushed.
Wrapping it up
There you have it. We now have a program that is written in Objective-C, using C’s native GTK+ ‘bindings’ for the GUI, that can call both regular C and Objective-C functions and code. In addition, thanks to the porting of both GTK+ and GNUstep to Windows, this same code will also produce a cross-platform application that works on both Mac OSX and Windows.
This post was originally published on June 15, 2014. The original can be found here. Note that there are other direct, compatible, alternatives and proper successors to TrueCrypt these days, including VeraCrypt. This post is simply about a different option available to Linux users.
With the recent questions surrounding the security of TrueCrypt there has been a big push to move away from that program and switch to alternatives. One such alternative, on Linux anyway, is the Linux Unified Key Setup (or LUKS) which allows you to encrypt disk volumes. This guide will show you how to create encrypted file volumes, just like you could using TrueCrypt.
The Differences
There are a number of major differences between TrueCrypt and LUKS that you may want to be aware of:
TrueCrypt supported the concept of hidden volumes, LUKS does not.
TrueCrypt allowed you to encrypt a volume in-place, without losing data, LUKS does not.
TrueCrypt supports cipher cascades where the data is encrypted using multiple different algorithms just in case one of them is broken at some point in the future. As I understand it this is being talked about for the LUKS 2.0 spec but is currently not a feature.
If you are familiar with the terminology in TrueCrypt you can think of LUKS as offering both full disk encryption and standard file containers.
How to create an encrypted LUKS file container
The following steps borrow heavily from a previous post so you should go read that if you want more details on some of the commands below. Also note that while LUKS offers a lot of options in terms of cipher/digest/key size/etc, this guide will try to keep it simple and just use the defaults.
Step 1: Create a file to house your encrypted volume
The easiest way is to run the following commands which will create the file and then fill it with random noise:
# fallocate -l <size> <file to create>
# dd if=/dev/urandom of=<file to create> bs=1M count=<size>
For example let’s say you wanted a 500MiB file container called MySecrets.img, just run this command:
Here is a handy script that you can use to slightly automate this process:
#!/bin/bash
NUM_ARGS=$#
if [ $NUM_ARGS -ne 2 ] ; then
echo Wrong number of arguments.
echo Usage: [size in MiB] [file to create]
else
SIZE=$1
FILE=$2
echo Creating $FILE with a size of ${SIZE}MB
# create file
fallocate -l ${SIZE}M $FILE
#randomize file contents
dd if=/dev/urandom of=$FILE bs=1M count=$SIZE
fi
Just save the above script to a file, say “create-randomized-file-volume.sh”, mark it as executable and run it like this:
There are ways to do this in the terminal but for the purpose of this guide I’ll be showing how to do it all within gnome-disk-utility. From the menu in Disks, select Disks -> Attach Disk Image and browse to your newly created file (i.e. MySecrets.img).
Don’t forget to uncheck the box!
Be sure to uncheck “Set up read-only loop device”. If you leave this checked you won’t be able to format or write anything to the volume. Select the file and click Attach.
This will attach the file, as if it were a real hard drive, to your computer:
Next we need to format the volume. Press the little button with two gears right below the attached volume and click Format. Make sure you do this for the correct ‘drive’ so that you don’t accidentally format your real hard drive!
Please use a better password
From this popup you can select the filesystem type and even name the drive. In the image above the settings will format the drive to LUKS and then create an ext4 filesystem within the encrypted LUKS one. Click Format, confirm the action and you’re done. Disks will format the file and even auto-mount it for you. You can now copy files to your mounted virtual drive. When you’re done simply eject the drive like normal or (with the LUKS partition highlighted) press the lock button in Disks. To use that same volume again in the future just re-attach the disk image using the steps above, enter your password to unlock the encrypted partition and you’re all set.
But I don’t even trust TrueCrypt enough to unlock my already encrypted files!
If you’re just using TrueCrypt to open an existing file container so that you can copy your files out of there and into your newly created LUKS container I think you’ll be OK. That said there is a way for you to still use your existing TrueCrypt file containers without actually using the TrueCrypt application.
First install an application called tc-play. This program works with the TrueCrypt format but doesn’t share any of its code. To install it simply run:
# sudo apt-get install tcplay
Next we need to mount your existing TrueCrypt file container. For the sake of this example we’ll assume your file container is called TOPSECRET.tc.
We need to use a loop device but before doing that we need to first find a free one. Running the following command
# sudo losetup -f
should return the first free loop device. For example it may print out
/dev/loop0
Next you want to associate the loop device with your TrueCrypt file container. You can do this by running the following command (sub in your loop device if it differs from mine):
# sudo losetup /dev/loop0 TOPSECRET.tc
Now that our loop device is associated we need to actually unlock the TrueCrypt container:
# sudo tcplay -m TOPSECRET.tc -d /dev/loop0
Finally we need to mount the unlocked TrueCrypt container to a directory so we can actually use it. Let’s say you wanted to mount the TrueCrypt container to a folder in the current directory called SecretStuff:
# sudo mount -o nosuid,uid=1000,gid=100 /dev/mapper/TOPSECRET.tc SecretStuff/
Note that you should swap your own uid and gid in the above command if they aren’t 1000 and 100 respectively. You should now be able to view your TrueCrypt files in your SecretStuff directory. For completeness sake here is how you unmount and re-lock the same TrueCrypt file container when you are done:
So what is the best Linux distro? If you know Linux you may know that there are a lot and a lot of Linux distros out there and you can check most of them from distro watch website
You may try few of them so what is the difference between them and which one of them suitable for you and what is the best Linux distro?
Well that question needs you to walk around and what other provide and Pros and Cons of everyone but I gather some information from the web about the most used and loved distros that you might use and fit yourself with one of them
I’m going to walk through every one of those distros and you will choose the best Linux distro yourself according to your needs
Elementary OS: Elegant Looking and fast speed
best Linux distro elementary-os
Elementary OS is a Linux distribution based on Ubuntu. It uses Pantheon desktop environment which gives the distro the beautiful looking and lightweight on your PC
So if your concern about the best looking this is the best Linux distro for you
They call this distro Mac OS X of the Linux because it is the best Linux distro for laptops and desktops some people might say they do not prefer it because of the desktop environment which is called Cinnamon But now it is LTS (long term support) and is more stable than ever and developers of that desktop spend a lot of time to make it better than ubuntu so if you are searching about powerful computing this is the best Linux distro that you might need
If you check the servers around the world you will notice that the huge percent of servers uses centos specially and this is because of one very important thing
The famous and cool hosting control panel cPanel runs only on CentOS
And for many people that might let them choose it
So for Servers CentOS is the best distro that you should go with
Arch Linux is the best Linux distro for those who want to learn everything about Linux
Experts categorize this distro as the most customizable Linux distro on the web and with the rich documentation on their website that makes it the best one Geeks
Many gamers use windows for gaming and if they love Linux they may dual boot with Linux till coming to that distro of Linux which is dedicated for gamers and games so if you are a gamer this is the best onefor you
Keep in mind that all the mentioned distros are the best when writing that article, the world is changing everyday who knows what will be the best next? see you then
Historically linux distributions have created a dedicated partition to be used as swap space and while this does come with some advantages there are other issues with it as well. Being a fixed size partition means it is relatively difficult to later change your mind about how much swap your system actually needs.
Thankfully there is another way: using a swap file instead of a swap partition.
To do this all you need to do is create a file that will hold your swap, set the right permissions to it, format it and use it. The ArchWiki has an excellent guide on the whole process here but I’ve re-created my steps below.
I like to use fallocate but you could also use dd or whatever. For example the following will create a 2GB swap file in the root directory:
sudo fallocate -l 2G /swapfile
Next up set the permissions:
sudo chmod 600 /swapfile
Format it:
sudo mkswap /swapfile
Use it:
sudo swapon /swapfile
That’s pretty much it. At this point you have the ability to add as much swap (via swap files) as you’d like. If you ever want to stop using swap, for example to get rid of the file when you’re done, simply issue the following command:
sudo swapoff /swapfile
One other thing to note is that every time you reboot your system you will have to re-run the swapon command above. To avoid this you can add it to your fstab file so that it is done on startup.
/swapfile none swap defaults 0 0
The nice thing about using swap files is that they are really flexible, allowing you to allocate as much or as little as you need at any given time.
This post was originally published on October 29, 2010. The original can be found here.
Overview and Introduction
I’ve been dabbling with managing a VOIP server for the past year or so, using CentOS, Asterisk and FreePBX on a co-located server. Recently Dave and I needed to move to our own machine, and decided to use TEH CLOUD to reduce management and get a fresh start. There are hundreds of hosts out there offering virtual private servers (VPS’s). We’ve standardized on Linode for our small business for a few reasons. While I don’t want to sound like a complete advertisement, I’ve been incredibly impressed with them:
Performance. The host systems at Linode run at least 4-way 2GHz Xeon dual-core CPUs (I’ve seen higher as well) and you’re guaranteed the RAM you pay for. Pricing is generally based on how much memory you need.
Pricing. For a 512MB Linode, you pay $19.95 US per month. Slicehost (a part of Rackspace, and a Linode competitor) charges the same amount for a 256MB slice. Generally you want at least 512MB RAM for a Linux machine that’s not a test/development box.
Features. If you have multiple VMs in the same datacenter, you can assign them private IPs and internal traffic doesn’t count toward your bandwidth allowance. Likewise, bandwidth is pooled among all your VMs; so buying two VMs with 200GB bandwidth each gives 400GB for all your systems.
With full root access and the Linux distribution of your choice, it’s very easy to set up and tear down VMs.
Why VOIP?
When people hear VOIP, they generally assume either a flaky enterprise system with echoing calls or something like Skype. Properly configured, a VOIP system offers a number of really interesting features:
Low-cost long distance and international calling. The provider we use, voip.ms, offers outgoing calls for $0.0052 per minute to Canada and $0.0105/minute to the US on their value route.
Cheap phone numbers – direct inward dialing – are available for $0.99 per month in your region. These phone numbers are virtual and can be configured to do nearly anything you want. Incoming calls are $0.01/minute, and calls between voip.ms numbers are free.
Want to take advantage of cheap long distance from your cell phone? Set up a Direct Inward System Access path, which gives you a dial tone for making outgoing calls when you call a local number. Put your DID number on your My5 list, and you’re set to reduce bill overages.
Voicemail becomes much more useful when the VOIP server sends you an email with a WAV attachment and caller ID information.
Want to set up an interactive voice response menu, time conditions, blacklist telemarketers, manage group conferences or have witty hold music? All available with FreePBX and Asterisk.
Continue reading for server setup details and security best practices…
Configuration
I opted to use Ubuntu 10.04 LTS on the server, since there are handy directions for configuring Asterisk and FreePBX. The guide is pretty handy, but some adjustments had to be made to the article for the latest versions of Ubuntu and Asterisk:
When installing Asterisk, make sure to install the sox package for additional sound and recording support.
Back up your /etc/asterisk/modules.conf file before installing FreePBX, and then restore it after the installation is complete. The FreePBX installation seems to clobber this file.
Replace all instances of the asteriskcdr database with asteriskcdrdb for proper call reporting functionality. Likewise, you’ll have to recompile and install the asterisk-addons package as per Launchpad bug 560656:
Don’t use the amportal script for managing Asterisk/FreePBX; use
/etc/init.d/asterisk [start|stop|restart]
instead.
Let It Ring
There’s plenty of great FreePBX documentation available online – you shouldn’t have a problem getting up and running once the installation is finished. As always, you should follow best server security practices:
Enforce username/password authentication with .htaccess and htpasswd and HTTPS for your management console, or only expose FreePBX administration over localhost/127.0.0.1 and tunnel in. There are plenty of articles on configuring OpenSSL and Apache2.
Consider running SSH on an alternate port (not 22), and denying direct logins from the root user account. Enforce strong passwords and use tools such as fail2ban and DenyHosts to limit SSH attacks.
Use a firewall. Ubuntu’s ufw is very simple to manage. For an Asterisk server, you’ll want to allow UDP ports 5060 and 10000-20000 (for voice traffic), or a range defined in
/etc/asterisk/rtp.conf
Feel free to post comments here on server setup or general VOIP questions, and I’ll do my best to help out!
This post was originally published on September 26, 2010. The original can be found here.
Windows?? *GASP!*
Sometimes you just have to compile Windows programs from the comfort of your Linux install. This is a relatively simple process that basically requires you to only install the following (Ubuntu) packages:
To compile 32-bit programs
mingw32 (swap out for gcc-mingw32 if you need 64-bit support)
mingw32-binutils
mingw32-runtime
Additionally for 64-bit programs (*PLEASE SEE NOTE)
mingw-w64
gcc-mingw32
Once you have those packages you just need to swap out “gcc” in your normal compile commands with either “i586-mingw32msvc-gcc” (for 32-bit) or “amd64-mingw32msvc-gcc” (for 64-bit). So for example if we take the following hello world program in C
we can compile it to a 32-bit Windows program by using something similar to the following command (assuming the code is contained within a file called main.c)
You can even test to make sure it worked properly by running the program through wine like
wine Program.exe
You might need to install some extra packages to get Wine to run 64-bit applications but in general this will work.
That’s pretty much it. You might have a couple of other issues (like linking against Windows libraries instead of the Linux ones) but overall this is a very simple drop-in replacement for your regular gcc command.
*NOTE: There is currently a problem with the Lucid packages for the 64-bit compilers. As a work around you can get the packages from this PPA instead.
This post was originally published on July 4, 2010. The original can be found here.
Recently I decided to try out PowerTOP, a Linux power saving application built by Intel. I am extremely impressed by how easy it was to use and the power savings I am now basking in.
PowerTOP is a terminal application that first scans your computer for a number of things during a set interval. It then reports back which processes are taking up the most power and offers you some options to improve your battery life. All of these options can literally be enabled at a press of a button. It’s sort of like an experience I once had with Clippy in Microsoft Word; “it seems you are trying to save power, let me help you…” After applying a few of the suggestions the estimated battery life on my laptop went from about 3 and a half hours to almost 5 hours. In short, I would highly recommend everyone at least try out PowerTOP. I’m not promising miracles but at the very least it should help you out some.
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