LPI Linux Certification in a Nutshell Part 20

Set swap size to be somewhere between one and two times the size of main memory.

/proc The /proc /proc filesystem includes information on interrupts, I/O ports, and DMA in filesystem includes information on interrupts, I/O ports, and DMA in /proc/interrupts /proc/interrupts, /proc/ioports /proc/ioports, and /proc/dma /proc/dma.

Objective 102.2: Install a Boot Manager LILO LILO has historically been the default Linux boot loader.

LILO consists of the lilo lilo command, which installs the boot loader, and the boot loader itself. command, which installs the boot loader, and the boot loader itself.

LILO is configured using /etc/lilo.conf /etc/lilo.conf.

Any modification to the /etc/lilo.conf /etc/lilo.conf file requires the file requires the lilo lilo command to be rerun. command to be rerun.

GRUB GRUB can boot Linux as well as most other PC-based operating systems.

GRUB relies on various files in the /boot/grub /boot/grub directory to support reading from various types of filesystems. directory to support reading from various types of filesystems.

GRUB is configured using /boot/grub/menu.lst /boot/grub/menu.lst (or (or /boot/grub/grub.conf /boot/grub/grub.conf on some distributions). on some distributions).

GRUB can be configured to present a text or graphical menu interface and also has a command-line interface.

Modifications to the GRUB configuration files do not require the grub grub command to be re-run (unlike LILO). command to be re-run (unlike LILO).

Objective 102.3: Manage Shared Libraries Concepts System libraries provide many of the functions required by a program.

A program that contains executable code from libraries is statically linked statically linked because it stands alone and contains all necessary code to execute. because it stands alone and contains all necessary code to execute.

Since static linking leads to larger executable files and more resource consumption, system libraries can be shared among many executing programs at the same time.

Commands A program that contains references to external, shared libraries is dynamically linked dynamically linked at runtime by the dynamic linker, at runtime by the dynamic linker, ld.so ld.so.

New locations for shared libraries can be added to the LD_LIBRARY_PATH LD_LIBRARY_PATH variable. As an alternative, the locations can be added to variable. As an alternative, the locations can be added to /etc/ld.so.conf /etc/ld.so.conf, which lists library file directories. After this, you must run /sbin/ldconfig /sbin/ldconfig to translate this file into the binary index to translate this file into the binary index /etc/ld.so.cache /etc/ld.so.cache.

Objective 102.4: Use Debian Package Management Commands dpkg automates the installation and maintenance of software packages and offers a number of options. automates the installation and maintenance of software packages and offers a number of options.

dselect uses a text-based interactive menu to select (or deselect) packages for installation. uses a text-based interactive menu to select (or deselect) packages for installation.

alien can convert packages to and from the RPM and Debian package format. can convert packages to and from the RPM and Debian package format.

apt-get is a powerful tool that interfaces with online repositories of Debian packages to install and upgrade packages by name and resolves each package's dependencies automatically. is a powerful tool that interfaces with online repositories of Debian packages to install and upgrade packages by name and resolves each package's dependencies automatically.

Objective 102.5: Use Red Hat Package Manager (RPM) Concepts RPM automates the installation and maintenance of software packages.

Package dependencies are defined but not resolved automatically.

-i, -e -e, -U -U, -v -v, -h -h, --nodeps --nodeps, and --force --force are common options. are common options.

The yum yum command is a frontend to RPM, interacting with online software repositories to download and install software automatically. command is a frontend to RPM, interacting with online software repositories to download and install software automatically.

The command yum update yum update will search for updates to installed packages, download them, resolve dependencies, and install them automatically. will search for updates to installed packages, download them, resolve dependencies, and install them automatically.

GNU and Unix Commands Objective 103.1: Work on the Command Line The interactive sh.e.l.l and sh.e.l.l variables A sh.e.l.l sh.e.l.l provides the command prompt and interprets commands. provides the command prompt and interprets commands.

A sh.e.l.l variable sh.e.l.l variable holds a value that is accessible to sh.e.l.l programs. holds a value that is accessible to sh.e.l.l programs.

PATH is a sh.e.l.l variable that contains a listing of directories that hold executable programs. is a sh.e.l.l variable that contains a listing of directories that hold executable programs.

Commands must be bash bash built-ins, found in the built-ins, found in the PATH PATH, or explicitly defined in order to succeed.

When sh.e.l.l variables are exported exported, they become part of the environment environment.

Entering commands Commands are comprised of a valid command, with or without one or more options and arguments, followed by a carriage return.

Interactive commands can include looping structures more often used in sh.e.l.l scripts.

Command history, editing, and subst.i.tution Sh.e.l.l sessions can be viewed as a conversation. History, expansion, and editing make that dialog more productive.

Commands can be reissued, modified, and edited. Examples are shown in Table10-3 Table10-3.

Command subst.i.tution allows the result result of a command to be placed into a sh.e.l.l variable. of a command to be placed into a sh.e.l.l variable.

Table10-3.Sh.e.l.l expansion, editing, and subst.i.tution examples

History type Examples Expansion !!

!n

^string1^string2 Editing Ctrl-P, previous line

Ctrl-K, kill to end of line

Ctrl-Y, paste (yank) text Subst.i.tution VAR=$(command) or or VAR='command' VAR='command'

Recursive execution Many commands contain either a -r -r or or -R -R option for recursive execution through a directory hierarchy. option for recursive execution through a directory hierarchy.

The find find command is inherently recursive, and is intended to descend through directories looking for files with certain attributes or executing commands. command is inherently recursive, and is intended to descend through directories looking for files with certain attributes or executing commands.

Objective 103.2: Process Text Streams Using Filters The commands The following programs modify or manipulate text from files and standard input: cat [file] [file]

Print file file to standard output. to standard output.

cut [files] [files]

Cut out selected columns or fields from one or more files files.

expand [files] [files]

Convert Tabs to s.p.a.ces in files files.

fmt [files] [files]

Format text in files files to a specified width by filling lines and removing newline characters. to a specified width by filling lines and removing newline characters.

head [files] [files]

Print the first few lines of files files.

join file1 file2 file1 file2 Print a line for each pair of input lines, one each from file1 file1 and and file2 file2, that have identical join fields.

nl [files] [files]

Number the lines of files files, which are concatenated in the output.

od [files] [files]

Dump files files in octal, hexadecimal, ASCII, and other formats. in octal, hexadecimal, ASCII, and other formats.

paste files files Paste together corresponding lines of one or more files into vertical columns.

pr [file] [file]

Convert a text file into a paginated, columnar version, with headers and page fills.

sort [file] [file]

Sort lines in file file alphabetically, numerically, or other ways. alphabetically, numerically, or other ways.

split [infile] [outfile] [infile] [outfile]

Split infile infile into a specified number of line groups; the output will go into a succession of files: into a specified number of line groups; the output will go into a succession of files: outfilea outfileaa, outfilea outfileab, and so on.

tac [file] [file]

Print file file to standard output in reverse line order. to standard output in reverse line order.

tail [files] [files]

Print the last few lines of one or more files.

tr [string1 [string2]] [string1 [string2]]

Translate characters by mapping from string1 string1 to the corresponding character in to the corresponding character in string2 string2.

unexpand [files] [files]

Convert s.p.a.ces to Tabs in files files.

uniq [files] [files]

Display only unique lines in files files that are already sorted. that are already sorted.

wc [files] [files]

Print counts of characters, words, and lines for files files.

The stream editor, sed sed is a popular text-filtering program found on every Unix system. It has the following syntax: is a popular text-filtering program found on every Unix system. It has the following syntax: sedcommand[files]

sed-ecommand1[-ecommand2][files]

sed-fscript[files]

Execute sed sed commands commands, or those found in script script, on standard input or files files.

Objective 103.3: Perform Basic File Management Concepts Filesystem creation prepares a disk device (or part.i.tion) for use. Linux usually uses the native ext3 ext3 (third extended) journaling filesystem, but it supports many other filesystem types. You can see a list of all the filesystems Linux supports by using the "l" option under the (third extended) journaling filesystem, but it supports many other filesystem types. You can see a list of all the filesystems Linux supports by using the "l" option under the fdisk fdisk command. command.

The Linux filesystem is arranged into a hierarchical structure anch.o.r.ed at the root directory root directory, or / /. Beneath this is a tree of directories and files.

Identification information for a filesystem object is stored in its inode inode (index node), which holds location, modification, and security information. Filesystems are created with a finite number of inodes. (index node), which holds location, modification, and security information. Filesystems are created with a finite number of inodes.

File and directory management commands The following commands are essential for the management of files and directories: bzip2 [options] [pattern] [options] [pattern]

Create or uncompress an archive with the bzip2 algorithm.

cp file1 file2 file1 file2 cp files directory files directory Copy file1 file1 to to file2 file2, or copy files files to to directory directory.

cpio[options] [files]

Create or extract a binary archive, containing either files or a recursive set of files and directories.

dd [options] [files] [options] [files]

Copy and convert files. The dd dd command can also copy data from raw devices, bypa.s.sing the filesystem layer. command can also copy data from raw devices, bypa.s.sing the filesystem layer.

file [file] [file]