installing softwares in linux
Well friends, generally when users from the Windows background enter the Linux arena, they find installation very difficulty. They are used to the luxury of double clicking on a setup file and getting their software installed. But this is not so in linux, though exceptions are there like when i tried to install, Quake 3, Unreal Tournament the process was quite automatic after a few commands, same with GIMP, when u try to use it for the first time. I have came across many such softwares. Installation of Java VM is also a good example of automatic installation, these files are distributed as .bin files. But even then this is not very common.
Though the installation instructions tell us what to do, we have no idea what these steps actually do.
These days most of applications are distributed as RPMs(RedHat Package Manager, by RedHat). Other format is .deb (by Debian Linux). If u need to install .deb application u can use , Alien, to covert .deb to .rpm. These two are widely known formats. Installing RPM is a simple task. I have places a E-Book MaximunRPM (in parts) , file size n file extension constraints on me, u can understand. You will need WinRAR to join these two parts of the file. For persons who are Mandrake fans like me, instead of using rpm command u can use urpmi, and advanced version of rpm by Mandrake for its users, or the graphical package manager. Installing RPMs under Mandrake is breeze.
Other method of distributing applications is through zipped format known as tarball(.tar) then gunzipped using gzip or gunzip (.gz). Actually .gz and .tar or .tar.gz or .tgz are just compressed formats. After unzipping the files, installtion is a matter of three commands in series (configure, make & make install). Now details about this format follows:
Details :
Generally you would get Linux software in the tarball format (.tgz, .tar.gz) This file has to be uncompressed into any directory using tar command. In case you download a new tarball by the name nav.tgz, then you would have to type the following command
$ tar xfvz nav.tgz or alternatively
$ gzip -dc nav.tgz |tar -xvf
From this command it must become clear that that these files are first get compressed using tar and then zipped using gzip or gunzip.
Execution of this command would create a directory within the current directory and unzip all the files within that new directory. Once this is complete the installation instructions ask you to execute the 3 (now famous) commands : configure, make & make install. Most of the us do this and successfully install their softwares. But most of the us have no idea what this really does.
Each software comes with a few files which are solely for the purpose of installation sake. One of them is the configure script. The user has to run the following command at the prompt
$ ./configure
This file is shell script.The above command makes the shell run the script named ' configure ' which exists in the current directory. The configure script basically consists of many lines which are used to check some details about the machine on which the software is going to be installed. This script checks for lots of dependencies on your system. For the particular software to work properly, it may be requiring a lot of things to be existing on your machine already. When you run the configure script you would see a lot of output on the screen , each being some sort of question and a respective yes/no as the reply. If any of the major requirements are missing on your system, the configure script would exit and you cannot proceed with the installation, until you get those required things.
The main job of the configure script is to create a ' Makefile ' . This is a very important file for the installation process. Depending on the results of the tests (checks) that the configure script performed it would write down the various steps that need to be taken (while compiling the software) in the file named Makefile.
If you get no errors and the configure script runs successfully (if there is any error the last few lines of the output would glaringly be stating the error) then you can proceed with the next command which is
$ make
' make ' is actually a utility which exists on almost all Unix systems. For make utility to work it requires a file named Makefile in the same directory in which you run make. As we have seen the configure script's main job was to create a file named Makefile to be used with make utility. (Sometimes the Makefile is named as makefile also, dont get fooled here linux is case senmsitive so Make and make are different)
make would use the directions present in the Makefile and proceed with the installation. The Makefile indicates the sequence, that Linux must follow to build various components / sub-programs of your software. The sequence depends on the way the software is designed as well as many other factors.
The Makefile actually has a lot of labels (sort of names for different sections). Hence depending on what needs to be done the control would be passed to the different sections within the Makefile Or it is possible that at the end of one of the section there is a command to go to some next section.
Basically the make utility compiles all your program code and creates the executables. For particular section of the program to complete might require some other part of the code already ready, this is what the Makefile does. It sets the sequence for the events so that your program does not complain about missing dependencies.
One of the labels present in the Makefile happens to be named ' install ' .
If make ran successfully then you are almost done with the installation. Only the last step remains which is
$ make install
As indicated before make uses the file named Makefile in the same directory. When you run make without any parameters, the instruction in the Makefile begin executing from the start and as per the rules defined within the Makefile (particular sections of the code may execute after one another..thats why labels are used..to jump from one section to another). But when you run make with install as the parameter, the make utility searches for a label named install within the Makefile, and executes only that section of the Makefile.
The install section happens to be only a part where the executables and other required files created during the last step (i.e. make) are copied into the required final directories on your machine. E.g. the executable that the user runs may be copied to the /usr/local/bin so that all users are able to run the software. Similarly all the other files are also copied to the standard directories in Linux. Remember that when you ran make, all the executables were created in the temporary directory where you had unzipped your original tarball. So when you run make install, these executables are copied to the final directories.
Thats it !! If u find something contradicting or u record a wrong fact or there is any error, please inform me about that. I can be reached at:
