Chapter 2 Linux

Shared library images

The files residing in the /lib directory that programmers use to run share code, rather than copying this code into other programs. Doing so makes their programs smaller and faster

Integrated Drive Electronics (IDE)

The most popular electronic hard disk interface for personal computers. This is the same as the ANSI ATA standard.

journaling

The process of keeping chronological records of data or transactions so that if a system crashes without warning, the data or transactions can be reconstructed or backed out to avoid data loss or information that is properly synchronized.

binaries

The programs residing in the /bin directory and elsewhere that are needed to start the system and perform other essential tasks.

d

subdirectory for permission

s

symbol for SGID

x

symbol for execute permission

g

symbol for group chmod

o

symbol for other chmod

u

symbol for owner chmod

r

symbol for read permission

t

symbol for sticky bit

w

symbol for write permission

parent

The directory in which a subdirectory is created and stored

directory

A special type o ffile that can contain other files and directories.

permission

A specific privilege to access and manipulate a directory or file

child

A subdirectory created and stored withing a parent directory

character special file

A UNIX/Linux I/O management file used to handle byte-by-byte streams of data, such as through serial or USB connections, including terminals, printers, and network communications.

subdirectory

A directory under a higher or parent directory

device special file

A file used in UNIX/Linux for managing I/O devices. It can be one of two types: Block special file or character special file

UNIX file system (ufs)

A hierarchical (tree structure) file system supported in most version of UNIX/Linux. It is expandable, supports large storage, provides excellent security, is reliable, and employs information nodes (inodes)

symbolic link

A name or file name that points to and lets you access a file using a different name in the same directory or a file using the same or different name in a different directory

Group ID (GID)

A number used to identify a group of users

/usr partition

A partition in which to store some or all of the nonkernel operating system programs that will be accessed by users

/var partition

A partition that holds temporarily created files, such as files used for printing documents and log files used to record monitoring and administration data.

/home partition

A partition that is on the home directory and provides storage space for all users' directories. A separate section of the hard disk, it protects and insulates users' personal files from the UNIX/Linux operating system software.

/boot partition

A partition that is used to store the operating system files that compose the kernel

Small Computer System Interface (SCSI)

A popular and fast electronic hard disk interface commonly used on network servers. It is actually a set of standards that defines various aspects of fast communications with a hard disk

extent

A portion of a disk, such as a block or series of blocks, that is reserved for a file and that represents contiguous space, so thatas the file grows, all of it remains in the same location on disk. Reduces file fragmentation on a disk, which reduces disk wear and the time it takes to retrieve information.

utility

A program that performs useful operations such as copying files, listing directories, and communication with other users. Unlike other operating system programs, this is an add on and not part of the UNIX/Linux shell, nor a component of the kernel

partition

A separate section of a disk that holds a file system and that is created so activity and problems occurring in other partitions do not affect it.

superblock

A special data block on a partition that contains information about the layering of blocks. This information is the key to finding anything on the file system, and it should never change.

information node, inode

A system for storing essential information about directories and files. Information includes: 1. The name of a directory or file] 2. General information about that directory/file 3. Information (a pointer) about how to locate the directory/file on a disk partition.

virtual file system

A system that occupies no disk space, such as the /proc directory. This references and lets you obtain information about which programs and processes are running on a computer

Bootstrap loader

A utility residing in the /boot directory that starts the operating system

Sticky bit

An executable permission that either causes a program to stay resident in memory (older systems) or ensures that only root or the owner can delete or rename a file (newer systems)

file system

An operating system's way of organizing files on mass storage devices, such as hard and floppy disks. The organization is hierarchical and resembles an inverted tree. In the branching structure, top-level files contain other files which in turn contain other files.

/lib

Directory that contains kernel modules and those shared library images (the C programming code library) needed to boot the system and run the commands in the root filesystem

set group ID (SGID) bit

Enables the owner of a program to keep full ownership, but also gives members of a group temporary ownership while executing that program

set user ID (SUID) bit

Enables the owner of a program to retain full ownership, but also gives an ordinary user temporary ownership while executing that program

hd

Partition label that identifies IDE hard disk interface

file

The basic component for data storage

hidden file

a file that the operating system uses to keep configuration information, among other purposes. File name begins with a dot (.).

pathname

a means of specifying a file or directory that includes the names of directories and subdirectories on the branches of a tree structure

Virtual memory

a memory resource supported by the swap partition, in which the system can swap information between disk and RAM allowing the computer to run faster and more efficiently.

absolute path

a path name that begins at the root file system directory and lists all subdirectories to the destination file.

relative path

a pathname that begins at the current working directory and lists all subdirectores to the destination file

swap partition

a section of the hard disk separated from other sections so that it functions as an extension of memory, which means it supports virtual memory. A computer system can use the space in this partition to swap information between disk and RAM so the computer runs faster and more efficiently.

physical file system

a section of the hard disk that has been formatted to hold files.

wildcard

a special character that can stand for any other character or in some cases a group of characters, and is often used in an argument such as ls "file.*".

enhanced IDE (EIDE)

an improved version of IDE that offers faster data transfer speeds and is commonly used in modern computers

SCSI, Main, First

break down "sda1" type: drive: partition:

IDE, Secondary, Fourth

break down hdb4 Type: Drive: Partition:

cp -b

copy option that makes a backup of the destination file if the copy will overwrite a file

cp -i

copy option that provides a warning when you are about to overwrite a file

cp -u

copy option that specifies to only overwrite if the file you are copying is newer than the one you are overwriting

/dev

directory that contains the special device files for all the devices.

block special file

in UNIX/Linux, a file used to manage random access devices that involve handling blocks of data, including CD/DVD drives, hard disk drives, tape drives, and other storage devices. Also called a block device file.

ls -a

ls option to show hidden files

ls -X

ls option to sort by extension

ls -S

ls option to sort by size of the file or directory

ls -t

ls option to sort by the time when the file or directory was last modified

ls -r

ls option to sort in reverse order

ls -l

ls option to view detailed information about files and directories

ls -i

ls option to view the inode value associated with a directory or file

-

normal file for permission

1

octal permission: execute

0

octal permission: no permissions

4

octal permission: read

5

octal permission: read/execute

6

octal permission: read/write

7

octal permission: read/write/execute

2

octal permission: write

3

octal permission: write/execute

owner, group ,all others

order of file permissions

sd

partition label that identifies SCSI hard disk interface

rm -i

rm option that causes the operating system to prompt to make certain you want to delete the file before it is actually deleted

hot fixes

the ability to automatically move data on damaged portions of disks to areas that are not damaged.

peripherals

the equipment connected to a computer via electronic interfaces.

Extended File System (ext or ext fs)

the file system designed for Linux that is installed, by default, in Linux operating systems. It enables the use of the full range of built-in Linux commands, file manipulation, and security.

root file system directory

the main or partent directory (/) for all other directories. The highest level of the file system.

mount

the process of connecting a file system to the directory tree structure, making that directory accessible.`

executables

the programs residing in the /bin directory that are needed to start the system and perform other essential tasks.

virtual storage

the storage that might be allocated via different disks or file systems (or both), but that is transparently accessible as storage to the operating system and users.