The kernel and its configuration in Linux

[Bruno007]

WHAT THE KERNEL

One can imagine the kernel as a kind of heart of the operating system.
In fact, it is nothing but a sort of "low-level program, which takes care of the processes (or programs running) and provides an interface between the application layer and the underlying hardware, its main tasks, in addition to filtering processes to the demands of the hardware, are those of keeping track of them, each one reserving space in memory and to manage what in computer terms is defined as "scheduling", a function which would ensure that all running programs can benefit from the CPU for processing.

In addition to the latest kernel downloaded (possibly stable ...), you will need the gcc compiler and at least approximate knowledge of the hardware of your PC: hard disk type you use (IDE or SCSI), CD- ROM (today should all be IDE or SCSI, but some remnants of the past used a proprietary controller), but also data related to the sound card, such as DMA or IRQ numbers. This information can we get the "latch" the dear and beloved Windows 9X simply by right clicking on "My Computer".

The Linux kernel

The Linux kernel, developed by the now ultra acclaimed Linus and other volunteers, is primarily distributed as source in C language, and it is precisely for this reason that must be completed "in person" to use it (a listing in C language can not in fact be run directly from your computer ... should be first transformed into a format usable directly - the executable format - through a phase that is called "compilation"). There are several versions of the kernel, as this is constantly being updated to improve performance and / or fix bugs in previous versions.

Kernel version:

There are contemporary in two different versions of the kernel source, an absolutely stable for the "normal" users and a more "experimental" (but highly stable in principle) for developers and geeks: now stable versions are those identified with the version 2.0.X, while developers have a version number 2.1.x To determine if a version of the kernel is stable or not you watch the second version number (the middle one): even numbers = stable, odd numbers = experimental (that is stable 2.0.X, 2.1.x is experimental).

[Bruno007]

ITS COMPLETION

Once you have determined the various hardware components and their addresses, should you enter as root on the PC and move first in the directory / usr / src ("cd / usr / src"); at this point we should find at least two directories (used the command "ls" to show the contents of the directory in question): one is called linux-2.0.x (kernel version, provided you have installed that contained in the distribution you have used and will almost certainly not the most recent available ), while the other is a link to that directory (or typing "cd linux-2.0.x" or "cd linux" will enter into circulation in the same directory). Since you have a newer version make sure to replace the springs with new ones obsolete. The operation in question is performed by the following commands (this is done of course in / usr / src):

1. mkdir linux-2.2.5 (create the directory that will contain the kernel version 2.2.5)
   
2. rm linux (removes the symbolic link that points to the old source directory linux-2.0.X
   
3. ln-s linux-2.2.5 linux (create a symbolic link called linux that points to the directory 2.2.5)
   
4. tar xzvf / percorso/linux-2.2.5.tar.gz (instead of the path must be changed to the location where you downloaded the source, this extract from the archive compressed kernel source and puts them in the directory linux-2.2. 5 created earlier).
   
5. rm-rf linux-2.0.x (remove the old source directory 2.0.X, added to the command rm-rf (remove) used to say "recursive and forced" as the command in question usually does not remove directories that are not empty).

[Bruno007]

At this point, enter the linux directory with a "linux cd" in order to perform the phase of development of the kernel, allowing you to choose which components to include the same in what will be the new heart of the PC. Depending on personal taste, there are three different commands to do this, the only difference is the interface you want to use:

1. make config (ascii mode: you see a list where you can select the components Y (yes), N (no) and M.
   
2. make menuconfig (text only but always characterized by the convenient menu to make your selection by pressing space).
   
3. make xconfig (to be used if you have active X Window System. It will allow you to select the kernel components with easy mouse clicks).

There are three types of choices to be allocated for the various components: you can include with a yes (if you used menuconfig asterisk), to exclude it with no (and in this case will not be compiled into the kernel), but you can also make a "module" with the letter "M". One will ask: what "module." Simply said, always to lighten the kernel and do not include within it components which are not used often, you can make them modular, in this case can be loaded and unloaded from memory as needed (if you use the modules I recommend you say yes to the support of kernel you will find between the different options: it makes sure that these operations are automatic and transparent to the user, otherwise you will have them to hand).

[Bruno007]

Code maturity level options: you should leave this entry as it is, or with one voice in this unselected
Loadable module support: add support for modules in the kernel (voice Enable loadable module support) also support kernel daemon: serves to load the kernel modules automatically.
General setup: In this menu you select the processor type, you enable the virtual math emulation (for those without it because it is in possession of such a 486SX processor) and memory is limited to less than 16 mega (This option is for some buggy motherboards of the past who could not manage a good memory). For a Pentium processor or higher coviene leave things as they are (unless you have a PPro: in this case you can specify this type of CPU).
Floppy, IDE and other block devices: This section is quite long, but fortunately there is very little change ... First, unless you are in possession of a motherboard that features the CMD640 or RZ1000 chipset, you should delete these two entries (90% of motherboards typically mount an Intel chipset, at least for now). For the rest leave everything as is.
Networking options: it is a good choice to leave the settings as they are!
SCSI support: the same thing for this menu ... If you do not have a SCSI controller or do not wish to have access to any writer turning EIDE ATAPI-SCSI emulation, leave everything disabled (default choice).
Network device support: in the case of a machine that connects to the Internet via a modem module selected as the "ppp" option selected also, again as a module, the "plip" may be helpful to create TCP / IP connections between two computers with a parallel null-modem cable. Finally, unless you have an ethernet card, I recommend that you uncheck the "ethernet" and leave everything else as is.
ISDN subsystem: if you do not have an ISDN connection leave everything as is, or with nothing selected.
CD-ROM driver: This item is in the kernel to include support for ATAPI CD-ROM (in short, those who use proprietary controller). If you have a CD-ROM ATAPI leave it unchecked.

[Bruno007]

Filesystems: Select the type of filesystem that the kernel will support once completed ... I suggest putting the filesystem as a module "minix" and 'extended' (you never know, could also be useful!), Selected to leave the "second extended (if unchecked will not want to boot the machine: is one that uses Linux for its partitions!), and select "yes" entries "native language support", "ISO9660" (the file system of CD-ROM!), "DOS FAT", "MSDOS" "FVAT" (long filenames in the partitions of Windows 95), "Codepage 423", "NLS ISO 8859-1" "proc". If you think you need to NFS (network file system, you need to import and export their file systems on the network) select it as a module. Leave the rest with the default settings.
Character devices: leave things as they are well, unless they posses a printer, in which case the board to select the "parallel printer support" as a form, because your printer is not an essential. NB: If you have a mouse other than serial (eg PS / 2) will also need to select the "mouse support" and click your mouse from the list.
Sound card support: If you have a sound card support to enable sound.
Kernel hacking: these two items ... for now should deselect them.
The setup process is completed! Now Occur then save the current configuration with the appropriate option and exit the program.

[Bruno007]

CONTROLS
make dep, make clean, make bzImage, make modules, make modules_install

This may take some time and, as usual, it is greatly influenced by the type of machine you are using.

• make dep, make clean: we need to clean up the sources of previous compilations, and if you have just installed new springs, you can also avoid these steps, but in any case it is good practice to run them (you never know ...).
• make zImage: compile the kernel core
• make modules, make modules_install: Compile and install the modules in the right place.

Ulrime The steps are:

1. Rename the old kernel (usually called vmlinuz) Old extension (you never know, might still serve, at least until you are sure that thou art the new kernel functions properly. In this case, delete).
2. NB If you can not find the directory where is located the old kernel, edit the lilo.conf file located in the etc directory ...
3. cp / usr/src/linux/arch/i386/boot/bzImage / vmlinuz (copy the new kernel in / usr/src/linux/arch/i386/boot / - ... the bzImage command - in the root directory and vmlinux calls it, just like the old one).
4. lilo (LInux used to upgrade the loader for it to load the new kernel).
5. shutdown-r now (will reboot the machine)

If after restarting the PC did not unusual messages and you are sure of the stability of the new kernel, you should delete the old directory to linux, or the 2.0.x. Note that start-ups could see some error messages claiming that the presence of modules "char-major-10", "net-pf-4" and "net-pf-5. You can safely ignore them, but if you feel uncomfortable, edit the file / etc / modules.conf and add the following lines:

alias char-major-10 off
alias net-pf-4 off
alias net-pf-5 off

At the next reboot everything will be settled.