RH133 redhat enterprise linux system administration

RH133
Redhat Enterprise Linux System
Administration

Unit 1

Installation

Hardware Overview

Kernel Support

Core support: CPU, Memory, Process

Management , Interrupt/Exception Handling etc.

Dynamically Loadable Kernel Modules

Device Drivers

Additional Functionality

User Mode Access to kernel facilities

System Calls and Signals

Filesystem Device Nodes

Network Interfaces


Are not accessed through a device node but instead are
accessed through a “network interface” abstraction.

CPU and Memory

Seven Supported Architectures: x86, Itanium2,
AMD64/EM64T, S/390, zSeries, iSeries, pSeries.

CPU Support on x86

Technical support for more than 2 physical CPUs only on
AS variant (may use Hyper-Threading)

Up to 32 Physical CPUs with SMP or hugemem kernel.

Memory support on x86

Technical support for more than 16 GB on AS or WS

Standard i686/athlon kernel: 4GB

SMP i686/athlon kernel: 16GB

Hugemem SMP kernel: 64GB

Preparing to Install

Read the RELEASE-NOTES file on the first
CD or at


Check Hardware Compatibility

Redhat Supported Hardware List

Hardware compatible with Redhat Linux

/>
XFree86 supported video cards.



/>
Multiboot systems

Redhat Enterprise Linux and the GRUB boot
loader can co-exist with other operating systems,
including the following:

Windows NT/2000/XP/2003

DOS, Windows 3.x/9x/ME

NetBSD, FreeBSD and other open systems.

Two major issues arise when implementing
multiboot systems:

Partitioning and the boot process.

A boot loader such as System Commander or

NTLDR is already on the system and will launch
GRUB as a secondary boot loader.

Device Node Examples

Block devices:

hd[a-t] IDE devices

sd[a-z]+ SCSI devices

fd[0-7] Standard floppy drives

md[0-31] software RAID metadisks

loop[0-15] loopback devices

ram[0-9] ramdisks

Character Devices:

tty[0-31] virtual consoles

ttyS[0-9]+ Serial ports

lp[0-3] Parallel Ports

null infinite sink ( the bit bucket)

zero infinite source of zeros


[u]random sources of random information

fb[0-31] framebuffer devices

Symbolic Links:

/dev/cdrom - - > /dev/hd[a-t], /dev/sd[a-z]+

/dev/modem - - > /dev/ttyS[0-9]+

/dev/pilot - - > /dec/ttyS[0-9]+

The RHEL Installer

First Stage Installer Images

diskboot.img – VFAT filesystem image for
bootable media larger than a
floppy

You will need to use the dd command to move this image to you media. For
instance:
dd <diskboot.img > /dev/sda

Floppy installation is no longer supported

boot.iso ISO9660 bootable CD image

Booting form boot.iso is the same as passing the askmethod argument to

the installer when booting from CD 1.

You can create a bootable CD using the cdrecord command. For instance
cdrecord dev=/dec/hdc boot.iso

pxeboot Directory

Pre-boot Execution Environment (PXE) provides for a diskless installation.

Read /usr/share/doc/syslinux-2.11/prelinux.doc

Second Stage Installer

Graphical or textual

Can be invoked in noprobe or Kickstart mode

Once located and loaded by the first stage, drives the remainder of the
installation process.

Installer Features

noprobe and Kickstart modes available

mediacheck tests media integrity

Multiple Interfaces:

Graphical


Starts X server and a GUI installer

Can be started in lowers mode.

Works with hard drive, CDROM, NFS Installation

Graphical is the default

Text

Menu-based terminal interface

Works with all installation methods (ftp and http)

RHEL Installation Overview

Language, Keyboard and mouse selection

Media selection if applicable

Disk partitioning

Bootloader configuration

Network and firewall configuration

Authentication Setup

Package Selection


X server configuration

Partitioning Hard Drives

Hard drives are divided into partitions.

Partitions normally contain file systems.

Primary, extended and logical partitions

The default filesystem is ext3

Multiple partitions may be assembled into a
larger virtual partitions: software RAID and
LVM

Filesystems are accessed via a mount
point, which is a designed directory in the
file system hierarchy.

Software RAID

Redundant Array of Inexpensive Disks

Multiple partitions on different disks combined
into one RAID device

Fault tolerance, larger disk size, performance

Install-time RAID levels:


RAID 0: Striping (no redundancy)

RAID 1: Mirroring

RAID 5: Striping with distributed parity

Configuring File Systems

Must select mount points, partition sizes,
and file system types in the installer

Can set up manually or automatically

There are many layouts which may be
used

/ mast include /etc, /lib, /bin, /sbin, /dev

Swap space is typically 2x physical RAM

Typical mount points: /boot, /home, /usr, /var,
/tmp, /usr/local, /opt

Network Configuration

Can configure each NIC independently

DHCP or static IP configuration


Determine if automatically activated on boot

LVM: Logical Volume Manager

Manages storage on one or more
partitions as virtual partitions, or logical
volumes

Real partitions are physical volumes and are
assigned to a volume group (a virtual disk)

Disk space in the volume group is divided into
extends which are assigned to a logical volume

Easy to resize logical volumes

Add a physical volume to the volume group
and assign the new extents to the logical
volume.

Firewall Setup

Installer can set up a kernel mode stateful
packet filter

Choice of two settings: “Enabled” and “No
Firewall”

“Trusted Devices” can bypass the firewall


Can allow access to arbitrary services.

Security Enhanced Linux

Access control determines what actions
processes can perform on what objects

Discretionary Access Control (Traditional Linux)

Users control permissions on objects

Mandatory Access Control (SELinux)

System policy restricts permission which can be
granted.

SELinux Installation Options

Installation Options:

Disabled

Warn (Permissive)

Active (default) (Enforcing)

Package Selection

Package Selection


Universally (“Everything”)

By predefined components

Defined in RedHat/base/comps.xml

Individually

Validating Installation

Virtual consoles during installation

Post-boot validation

dmesg and /var/log/dmesg

/var/log/messages

/root/install.log

GRUB drops to a prompts if there is a
problem loading files.

noprobe Mode and Driver Disks

Method for supporting hardware newer
than the install program

Used at install time for less common
hardware


Prompt for Driver Disk

When run in noprobe mode

When started with: linux dd

When no PCI devices are detected.

Post-Install Configuration

Setup Agent (firstboot)

Configure X window System if necessary

Set date and time

Register with Redhat Network and get updated
RPMs

Install additional RPMs or Redhat
Documentation from CDROM

Setup users

system-config-* configuration tools

Unit 2

System Initialization and Services

Boot Sequence Overview

BIOS initialization

Boot Loader

Kernel Initialization

init starts and enters desired run level by
executing:

/etc/rc.d/rc.sysinit

/etc/rc.d/rc and /etc/rc.d/rc?.d

/etc/rc.d/rc.local

X Display Manager if appropriate

BIOS initialization

Peripheral detected

Boot device selected

First sector of boot device read and
executed