9781111540036_PPT_ch02 (1)

SUSE Linux Enterprise Server Administration: CLA, LPIC-1 &

Linux+

Section 2Install SUSE Linux Enterprise Server 11

SUSE Linux Enterprise Server Administration: CLA, LPIC-1 & Linux+

Objectives

• Understand Partitions, LVM, RAID, and File Systems

• Perform a SLES 11 Installation

• Understand the File System Hierarchy Standard (FHS)

2


Understand Partitions, LVM, RAID, and File Systems

• Before beginning an installation, you need to decide how to use the available hard disk space– Division should take into account intended uses

• Hard disks can be logically divided into smaller portions called partitions– Primary partition: continuous range of cylinders

• Limited to four primary partitions on x86 systems

– Extended partition: continuous range of cylinders that can be subdivided into logical partitions

• One primary partition can be an extended partition

– Logical partition: exists within an extended partition3


Design Guidelines for Implementing Partitions

• YaST proposes a partitioning scheme consisting of a swap partition and another partition using the rest of the disk space– If partition already exists, YaST tries to maintain it

• When implementing your own partitioning scheme– If hard disk < 4GB, use one partition for swap and

one for root (/)– If hard disk > 4GB:

• Create swap partition and root partition

• Can create separate partitions for different directories

– Candidates: /boot/, /opt/, /usr/, /var/, /srv/, /home/4


Design Guidelines for Implementing Partitions (continued)

• If partitioning is performed by YaST and other partitions are detected, they are entered in /etc/fstab to enable easy access to the data– Specified with noauto and user options– Not automatically entered with the exec option

• Linux hard drive names are /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd

• Partitions follow naming convention for the hard drive, followed by a partition number

5


Design Guidelines for Implementing Partitions (continued)

6

Table 2-1 Device Name for Hard DrivesCourtesy Course Technology/Cengage Learning

Table 2-2 Device Name for PartitionsCourtesy Course Technology/Cengage Learning


Understand Logical Volume Manager and Software RAID

• Logical Volume Manager (LVM): provides high level view of disk storage– Used to create, manage, and resize logical volumes

• Conventional partitioning of hard disk is inflexible

• LVM provides a volume group – pool of memory space– Space used to generate logical volumes

• Accessed by OS like conventional physical partitions

– Lets you resize the physical media during operation without affecting the applications

7


Understand Logical Volume Manager and Software RAID (continued)

• Basic structure of LVM includes:– Physical volume: partition or entire hard disk– Volume group: one or more physical volumes

grouped together• Add hard disk in a running system

• Use several hard disks with improve performance in RAID 0 mode

– Logical volume: part of volume group• Enlarge if there is space, added in running system

• Can reach very large size, no limit on the number

• Snapshot feature enables consistent backups

8


Understand Logical Volume Manager and Software RAID (continued)

9

Figure 2-1 LVM ComponentsCourtesy Course Technology/Cengage Learning


Software RAID

• RAID: used to combine hard disk partitions into one large virtual hard disk for optimizing performance– Hardware RAID: hard disks are connected to a

separate RAID controller• Seen by OS as one device, no additional RAID

configuration necessary at OS level

– Software RAID: hard disks combined by the OS• OS sees each disk and needs to be configured to use

them as RAID system

• Provides comparable performance and data security as Hardware RAID

10


Software RAID (continued)• RAID levels are determined by method in which disks

are combined and by their number– RAID 0: two or more hard disks pooled together

• Known as striping

– RAID 1: data is copied to one or more had disks• Known as hard disk mirroring

– RAID 5: data and a checksum are distributed across the hard disks

• Minimum number of disks is three

– RAID 6: comparable to RAID 5, two disks can fail without data loss

• Minimum number of disks is four

11


Select a Linux File System

• To use partition or logical volume it must have a file system– Linux OS used to create and manage file systems

• Each file system has strengths and weaknesses

• Does not replace backup strategy

• Types of file systems– Traditional file systems: do not journal data – Journaling file systems: logs changes to a journal

before writing them to main file system– Network file systems: remote file systems included in

file system tree12


Virtual File System Switch

• For a user or program, doesn’t matter what file system format is used– Same interface to the data always appears– Interface implemented by Virtual File System Switch

(VFS)• Abstraction level in the kernel providing defined

interfaces for processes

• Includes functions such as open file, write to file, read from file

• Displays file characteristics to the user as they are known from UNIX file system formats

13


Virtual File System Switch (continued)

14

Figure 2-1 LVM Components Courtesy Course Technology/Cengage Learning


Linux File System Internals

• In Linux file systems data and administration information are kept separate– Each file described by an inode

• Contains all information about a file except its name

• Must include inode for each file and directory

• 128 bytes in size

• Contains links to data blocks of the file

– Data organization differs between file system formats

15


Ext2fs File System Format

• Ext2 file system format is similar to traditional UNIX file system formats– Maximum number of files and inodes are specified at

file system creation• Inode density can be set at file system creation

– Block size specified at file system creation• Determines how much space is reserved for a file

• The larger the value, the more space consumed by the file, even if amount of data is smaller

– Filename can be up to 255 characters, path up to 4096 characters

16


Ext2fs File System Format (continued)

• Data is stored in a linear block group, containing:– Boot sector: static information about file system– SuperBlock: read when file is mounted, contains

information about the file system– Group descriptor: information on the other locations– Block bitmap: information indicating which blocks in

the group are free or occupied– Inode bitmap: information indicating which inodes

are free or occupied– Inode table: file information– Data blocks: where actual data is located

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Ext2fs File System Format (continued)

18

Figure 2-3 ext2 File System StructureCourtesy Course Technology/Cengage Learning


ReiserFS Format

• Organizes data differently than ext2– Fixed block size of 4096 bytes, but small files and

ends of files stored together in the same block– Inodes created only when they are actually needed– Faster access to files

• Use of balanced binary trees in organization of data blocks

• Require more processing power

– Filename can be up to 255 characters long– Path can be up to 4096 characters long, including

slashes19


Directories

• Contain filenames and the number of the inode for the file– Serve as tables

• Inode numbers are assigned line by line to filenames

• View the inode number using the ls –i command

– Inodes are uniquely defined on one partition only• Same inode number can exist on different partitions

– “.” file: link to the current directory– “..” file: link to previous layer in the direction of the

root

20


Links

• Link: File that points to another file– Hard link: another entry in a directory that points to

the inode of a file that already has a file name• Link and original file are indistinguishable

• Created using ln command

• File and link must be in the same partition, because inodes are unique only within a partition

– Symbolic link: file of its own that points to another file in the file system

• Link has different inode than original file

• Created using ln –s command

21


File System Journaling

• File systems: databases that store files and use metadata to organize and locate files on disk

• When modify a file system carries out two separate transactions– Can result in differences between data and metadata

• Requires file system check and possibly repair

• A journal based file system records of current transactions kept and updated upon completion– In case of corruption, need to check what

transactions were not completed

22


Perform a SLES 11 Installation

• The installation process includes multiple tasks

• To start installation process insert installation DVD in system optical drive and reboot the computer– Can select from various options of how to proceed:

• Boot from hard disk (default)

• Installation: starts normal installation process

• Repair installed system: graphical repair utility

• Rescue system: minimal system for troubleshooting

• Check installation media

• Firmware test: starts a BIOS checker

• Memory test: tests RAM using read/write cycles23


Perform a SLES 11 Installation (continued)

• Series of function keys placed at bottom of screen– Can be used to change variety of installation settings

• YaST installation dialog user interface:– Left panel: overview of installation status– Right panel: displays current installation step

• Lower left corner: help button for information about current installation step

• Lower right side: buttons used to navigate to previous or next installation step or to abort installation

• Language dialog: used to select language and keyboard layout and agree to license agreement

24


Check the Installation Media and Select the Installation Mode

• It is recommended to verify that the installation media is valid– If verification fails, do not continue the installation

• Obtain replacement copy of installation media

– If verification succeeds, system hardware is probed and corresponding basic kernel drivers are loaded

• Select the installation mode from following options:– New installation: normal new installation, default– Update: updates SLES 10 installation to SLES 11– Repair installed system

25


Set the Clock and Time Zone and Specify the Server Base Scenario

• Configure clock and time zone– YaST sets time zone based on language selection

• If hardware clock set to UTC, system time set according to time zone and automatically adjusted

• Specify the server’s base scenario:– Physical machine: used on physical hardware

without XEN– Virtual machine: used in a para-virtualized virtual

machine environment– XEN Virtualization host: machine that will function as

host for XEN virtual machines26


Configure Installation Settings and Verify Partitioning

• YaST analyzes the system and creates an installation proposal– Proposed settings are displayed, and can be

changed, in the overview tab and in the expert tab– In most cases, YaST partitioning scheme is

reasonable, but may be changed:• To optimize partitioning for special purpose server

• To configure LVM

• To configure software RAID on more than one drive

• To delete existing OSs to free space for SLES 11 installation

27


The Basic Linux Partitioning Scheme and Changing the Default Partitioning

Proposal• Optimal partitioning scheme for a server depends on

the purpose of the server

• SLES installation needs at least two partitions:– Swap partition: Extends the physically available

system RAM– Root partition: holds the root directory (/)

• Change default partitioning proposal to create partitions for directories in the file system– Adds a degree of stability to the system– Use YaST Expert Partitioner to do this

• Entry with information for each partition on hard disk28


Create New Partitions and Edit Existing Partitions

• Use YaST Expert Partitioner to create new partition– The options displayed depend on the specific hard

disk setup– Need to specify partition type, size, format,

encryption, and mount options

• To edit an existing partition, select it from the YaST Expert Partitioner list– Can only edit primary and logical partitions– Can change all the options about a partition except

its size

29


Delete and Resize Existing Partitions

• Use Expert Partitioner to delete a partition– Select partition from list, and click delete– Deleting extended partition deletes all logical

partitions

• Use Expert Partitioner to resize a partition– Backup data before resizing partition– Resize partition by moving slider until enough

unused disk space is available for the resized partition

30


Select Software

• SLES 11 includes variety of software packages– Patterns: categories of packages based on function

• Can be selected for installation as a group

• YaST often preselects software patterns by default

• Package contains application and supporting files– Several applications bundled into one package– Some packages are dependent on other packages

to be installed• Dependency information stored within RPM package

• YaST automatically adds dependent software packages to installation proposal

31


Select Software (continued)

• Possible displays for packages:– Patterns– Package groups: hierarchical tree view

• Several main groups, which can include subcategories

– Language: support for additional languages– Repositories: configured installation sources– Search: search for packages– Installation summary

• Need to confirm package selection for YaST to start package installation

32


Start the Installation Process and Set the root Password

• Start installation after customizing installation proposal– Can always return to the installation proposal

• Before installing software, YaST changes hard disk partitioning– After changing partitions and configuring them, installs

software and reboots

• Set password for root user, who has unlimited access to do anything– Should be used only for administrative tasks– Password should be hard to guess

33


Set the Hostname and Configure the Network

• YaST suggests default hostname of linux-xxxx– xxxx = random characters

– Change values to be suitable for the network• Can change hostname via DHCP or by writing it to /etc/hosts

• Set up network configuration on the server– Select if to configure network setting later or use or

adapt the configuration proposal• Proposal includes general network settings, firewall,

network interfaces, DSL connections, ISDN adapters, modems, VNC remote administration, and proxy

• Need to make sure to configure network cards

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Add a Network Card Manually

• Need to configure network card if not automatically detected:– Device type: network device type, e.g., Bluetooth– Configuration name: interface’s device number– Module name: select appropriate network card from

list• YaST loads the appropriate driver for selected card

• Additional configuration required for wireless device type– Need to configure WLAN and WEP Keys

35


Edit and Delete an Existing Configuration

• You can edit existing network interface configurations– Configure the address to be dynamic, statically

assigned IP address, and hostname and server name

– Need to set hostname, domain name, and routing

• To delete existing network card configuration, highlight it and press delete

• When finished changing network card, configurations save and return to proposal

36


Test the Internet Connection and Configure Novell Customer Center Configuration and Online Update

• Test connection to the Internet– Can choose to do this now or at a later stage, but

then can’t update the system during installation

• You can configure Novell Customer Center– Required to perform online updates

• Updates can be downloaded and installed to fix bugs or security issues

• Must register at Novell web site

• May need to select from a list of available patches to decide what updates are installed

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Configure Network Services

• Configure certificate authority (CA) and OpenLDAP server– Select to skip configuration or used automatically

generated configuration

– CA guarantees a trust relationship among communicating network services

• Can use default configuration or adapt it• If do not establish local CA, must secure server

communications using SSL and TLS

– Lightweight Directory Access Protocol (LDAP) server• Stores user and group account data

– If not sure about correct settings, use YaST default

38


Manage Users

• Need to configure user authentication method to be one of the following:– Local: traditional file based authentication method

• This is the default

– LDAP: configures system as LDAP client– NIS: configures system as NIS client– Windows domain: configures server to use the user

and group accounts in the Windows domain for authentication

• If not sure what method to use, use Local

• Next steps depend on the method selected.

39


Add Local Users

• If selected Local as authentication method, need to create at least one regular user account on system– Information stored in /etc/passwd and /etc/shadow

– Information entered includes:• User’s full name• Login name• Password: should be at least eight characters, case

sensitive, special characters allowed• Receive system mail: email addressed to root account

are forwarded to this user• Automatic login • User management: lets you add more users

40


Configure the System as an LDAP Client

• If LDAP is the selected authentication method configure system as LDAP client– LDAP client: can configure the following:

• Addresses of LDAP servers

• LDAP base DN: search base context on server

• LDAP TSL/SSL: encrypts communication with server

• LDAP version 2: select if server supports only LDAP version 2

– Start automounter: provides information about automatic mounting of file systems

– Create new LDAP user

41


Configure Hardware

• Configure server hardware using YaST

• YaST provides hardware configuration proposal, including:– Graphic card and monitor setup

– Printer and printer server settings

– Sound card configuration

• Can change the automatically generated configuration

• Can skip hardware configuration at this point– Make sure settings of graphics card in configuration

proposal are correct

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Finalize the Installation Process

• The installation is complete after configuring hardware

• Clone this system for autoyast: causes an Auto YaST file to be generated– The file can be used to set up identical systems

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Understand the File System Hierarchy Standard (FHS)

• Linux File system is different than that of other OSs– File systems can be spread out over many devices

• Can be mounted any place in the hierarchy

– File name can be up to 255 characters • Can contain special characters

– Some characters have special significance for shells• To use without special meaning, character should be

preceded by a “\” to mask special meaning

– You can use language specific characters– Case sensitive

44


Hierarchical Structure of the File System

• Linux file system is hierarchical– Can be shown in the form of a tree

• Not limited to a local partition

• Begins at the root directory (/)

– A file is uniquely defined by its path• Absolute path: path starting from the root of the entire

filesystem tree

– Always begins with a / representing root directory

• Relative path: path starting from current directory

• Length of path limited to 4096 characters including slashes

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Hierarchical Structure of the File System (continued)

46

Figure 2-46 Content of the Root Directory

Courtesy Course Technology/Cengage Learning


Hierarchical Structure of the File System (continued)

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Figure 2-47 Absolute and Relative PathsCourtesy Course Technology/Cengage Learning


File System Hierarchy Standard• Structure of file system described in File System

Hierarchy Standard (FHS)– Specifies which directories must be located on the first

level after the root and what they contain– Defines two layered hierarchy

• Directories in the top layer• Directories under /usr/ and /var/

• root directory is highest layer of FHS tree– Normally contains only directories – First to mount at boot time

• All programs that run at system start must be on same partition

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File System Hierarchy Standard (continued)

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Figure 2-48 File System Hierarchy StandardCourtesy Course Technology/Cengage Learning


Essential Binaries for Use by All Users (/bin/) and Boot Directory (/boot/)• /bin/ contains important binaries that are

required when no other file systems are mounted– Includes various shells, the most important

commands for working with files, commands for system analysis and configuration

• Boot directory (/boot/) contains system files– Static files related to the boot loader GRUB– Backed up information for the Master Boot Record

(MBR) and system map files– The kernel

• Has the file name vmlinuz50


Other Partitions (/data/) and Device Files (/dev/)

• When YaST finds other partitions or hard disks during the installation it creates mount points for each partition labeled datax

• Each hardware component in system represented by file in /dev/ directory– Files used to address hardware components

• Character oriented device files• Block oriented device files• Major number: identifies the number of the device driver to

be used• Minor number: identifies a specific device• Special device files can be generated using mknod

51


Configuration Files (/etc/) and User Directories (/home/)

• /etc/ and its subdirectories contain system configuration files and may not contain executables– Subdirectories may contain shell scripts– Most files are ASCII files

• Can be processed without editor

• Read by normal users, edited by root

• Every user has an area to work with files known as home directory located under /home/– Can be addressed using ~ shortucut– Includes individual configuration files

• Hidden files, names begin with a dot52


Libraries (/lib/) and Mount Point for Removable Media (/media/*)

• /lib/ contains libraries of standard functions that are called up only when a program runs– Used by programs in /bin/ and /sbin/ – Kernel modules located in /lib/modules/

• All files are arranged in one big tree which can include several devices

• mount command attaches device file system to tree

• Directories in /media/ directory used for mounting removable media when it is detected

53


Application Directory (/opt/) and Administrator’s Home Directory

(/root/)• /opt/ is used to store static files of installed

programs – Files stored in subdirectory named for the application

• /root/ is the home directory for the root user– Not located under /home/ like home directories for

normal users– Should be on same partition as root (/) directory

• Guarantees that root user can always log in without a problem to his own configured environment

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System Binaries, Data Directories for Services (/srv/), and Temporary

Area (/tmp/)• /sbin/ contains important programs for system

administration– Typically can be run by normal users, but only to

display the configured values• Changes to the configuration made by root user

• /srv/ directory contains subdirectories for containing data of various services

• /tmp/ stores temporary files created by various programs until these files are deleted

55


The Hierarchy Below /usr/, Variable Files (/var/), and Windows Partition

(/windows/)• /usr/ directory represents second hierarchical

layer– Location for all application programs, GUI files,

additional libraries, locally installed programs and shared directories containing documentation

• /var/ directory and subdirectories contain files that can be modified while system is running

• When YaST finds a partition with a Microsoft file system, creates a /windows/ directory– Subdirectories labeled with Windows drive

characters56


Process Files (/proc/)

• /proc/ makes process information available to user– Process information does not contain any real file or

occupy hard disk space– Generated dynamically when it is accessed– Each process has its own directory

• Values can be read as if it were a file

• Some values can be set by writing to corresponding “files”

– Also includes directories and files containing information about the state of the system

57


System Information Directory (/sys/) and Mount Point for Temporarily Mounted File Systems (/mnt/)

• /sys/ directory provides information about hardware buses, hardware devices, active devices, and their drivers– Information in the form of a tree– Does not contain any real files

• /mnt/ is standard directory for mounting file system– Should only be used for temporary purposes

• For permanent mount create a dedicated directory

– To remove mounted file system, use umount command

58


Directories for Mounting Other File Systems

• Other file systems can be mounted to the files system at any point – Directory must exist where you intend to mount the

new file system• Referred to as a mount point

• Anything contained in this directory is temporarily unavailable while new file system is mounted

– Typically only root user can mount and unmount– Use mount command to mount file system, and umount to unmount it

– Can share some directories with multiple computers

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Summary

• Storage space on hard drives divided into partitions

• Partitions must have a file system created on them

• LVM provides high level view of the disk storage on the system– Can be used to create logical volumes

• Software RAID allows combination of several disk to provide increased performance and redundancy

• Linux supports various file systems, some of which keep a journal and recover faster from crash

• SLES can be installed from various media

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Summary (continued)

• SLES installation includes many configuration steps

• Layout of Linux file system follows File System Hierarchy Standard

• FHS defines directory structure and purpose of directories within root directory (/) and below /usr/ and /var/ directories

• Some directories must exist on same partition as root directory (/), while others can be on different partitions or other machines

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