Some Basics of Linux

What is kernel?

The kernel is a program that constitutes the central core of a computer operating system. It has complete control over everything that occurs in the system.

A kernel can be contrasted with a shell (such as bash, csh or ksh in Unix-like operating systems), which is the outermost part of an operating system and a program that interacts with user commands. The kernel itself does not interact directly with the user, but rather interacts with the shell and other programs as well as with the hardware devices on the system, including the processor (also called the central processing unit or CPU), memory and disk drives

What is file system?

a file system (sometimes written filesystem) is the way in which files are named and where they are placed logically for storage and retrieval. The DOS, Windows, OS/2, Macintosh, and UNIX-based operating systems all have file systems in which files are placed somewhere in a hierarchical (tree) structure. A file is placed in a directory (folder in Windows) or subdirectory at the desired place in the tree structure.

File systems specify conventions for naming files. These conventions include the maximum number of characters in a name, which characters can be used, and, in some systems, how long the file name suffix can be. A file system also includes a format for specifying the path to a file through the structure of directories.

What is multi-user?

computer systems that support two or more simultaneous users. All mainframes and minicomputers are multi-user systems, but most personal computers and workstations are not. Another term for multi-user is time sharing.

What is GUI?

A graphical user interface (GUI) is a human-computer interface (i.e., a way for humans to interact with computers) that uses windows, icons and menus and which can be manipulated by a mouse (and often to a limited extent by a keyboard as well).

GUIs stand in sharp contrast to command line interfaces (CLIs), which use only text and are accessed solely by a keyboard. The most familiar example of a CLI to many people is MS-DOS. Another example is Linux when it is used in console mode (i.e., the entire screen shows text only).

Linux filesystem types?

minix, ext, ext2, ext3, xia, msdos, umsdos, vfat, proc, nfs, iso9660, hpfs, sysv, smb, ncpfs

For more detail about Filesystems click here

What is fdisk?

The program Microsoft operating systems MS-DOS and non-NT versions of Windows use to create partitions on hard drives. Technically, the program is called fdisk.exe. It uses a text-based interface. Windows 95b first added support for FAT-32 partitions into fdisk. Before that it only supported partitions up to 2 GB using FAT-16. This is also a slang term for wiping a drive out completely, as in "I'm going to F-Disk this drive if Windows crashes one more time!" There are several non-Microsoft equivalents to fdisk, but all serve similar purposes-to allow partitioning of hard disk drives.

For more details check fdisk man page

What is shell in linux?

A shell is a program that provides the traditional, text-only user interface for Unix-like operating systems. Its primary function is to read commands that are typed into a console (i.e., an all-text display mode) or terminal window (an all-text window) in a GUI (graphical user interface) and then execute (i.e., run) them.

The term shell derives its name from the fact that it is an outer layer of an operating system. A shell is an interface between the user and the internal parts of the operating system (at the very core of which is the kernel).

What is lilo?

Lilo means last in last out . LILO is a versatile boot loader for Linux. It does not depend on a specific file system, can boot Linux kernel images from floppy disks and hard disks, and can even boot other operating systems. One of up to sixteen differernt images can be selected at boot time. Various parameters, such as the root device, can be set indepenantly for each kernel. LILO can even be used as the master boot record.

What is Grub?

Grand Unified Bootloader (GRUB)" .A small software utility that loads and manages multiple operating systems (and their variants).

Where Is the Latest Kernel Version on the Internet?

The easiest way to update your kernel is to get the update directly from the distribution which you are running.

If you need or want to configure and compile your own kernel, the web page at http://www.kernel.org/ lists the current versions of the development and production kernels.

What is FSCK?

fsck - check and repair a Linux file system.

fsck is used to check and optionally repair one or more Linux file systems. filesys can be a device name (e.g. /dev/hdc1, /dev/sdb2), a mount point (e.g. /, /usr, /home), or an ext2 label or UUID specifier (e.g.UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root). Normally, the fsck program will try to handle filesystems on different physical disk drives in parallel to reduce the total amount of time needed to check all of the filesystems.

If no filesystems are specified on the command line, and the -A option is not specified, fsck will default to checking filesystems in /etc/fstab serially. This is equivalent to the -As options.

What is partition?

A partition is a section of a hard disk. When you format a hard disk, you can usually choose the number of partitions you want. The computer will recognize each partition as a separate disk, and each will show up under "My Computer" (Windows) or on the desktop (Macintosh).

What is a boot loader?

Most simply, a boot loader loads the operating system. When your machine loads its operating system, the BIOS reads the first 512 bytes of your bootable media (which is known as the master boot record, or MBR). You can store the boot record of only one operating system in a single MBR, so a problem becomes apparent when you require multiple operating systems. Hence the need for more flexible boot loaders.

The master boot record itself holds two things -- either some of or all of the boot loader program and the partition table (which holds information regarding how the rest of the media is split up into partitions). When the BIOS loads, it looks for data stored in the first sector of the hard drive, the MBR; using the data stored in the MBR, the BIOS activates the boot loader.

What is PAM?

(Pluggable Authentication Modules) A programming interface that enables third-party security methods to be used in Unix. For example, smart cards, Kerberos and RSA technologies can be integrated with various Unix functions such as rlogin, telnet and ftp.

What is default shell in linux?

Most of the Linux Distributions default shell is bash shell

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