linux boot order

• Bios check the system and launch the first stage boot loader on the MBR of the primary   hard disk

• First stage boot loader itself into memory and launch the second stage boot loader from boot partition

• The second stage boot loader   load the kernel into memory, which in turn load any modules& mount root partition, read only

• The kernel transfer control of the boot process to the /sbin/init program

• /sbin/init program load all service and user interface tool and mount all partition listed in /etc/fstab

• The user is presented with a login screen for freshly booted Linux system

                                                               

                                                                   System boot sequence

• Grub stage one load MBR

• Second stage  /boot/grub/stage1.5 (boot partition higher 1024 cylinder) 2

• /boot/grub/grub.conf  ----- see selection os menu

•  /boot/vmlinux.2.6.18-5.elxen load to ram

• initrd block device load (scsi)

• /etc/rc.d/rc.sysinit

• /etc/sysconfig/clock

• /etc/rc.serial

• /etc/inittab

• init – run level 5

• /etc/inittab run script called /etc/X11/prefdm (X display manger)

• /etc/X11

• gdm,kdm or xdm
• Depending on the content of the /etc/sysconfig/desktop file

• /usr/X11R6/bin/xorg

• /usr/X116/lib/modules

• /etc/X11

• /etc/X11/xorg.conf

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Posted in: Basics,How to,step by step,Update

Redhat Enterprise Linux version 6 aka RHEL6 features

Recently I attended one presentation from Redhat people on RHEL6 features. Some of the mesmerizing features as below.

• 85% more packages(Applications/softwares/tools) then RHEL5
• RHEL6 supports up to 4096 CPU’s
• RAM supported by RHEL6 is up to16TB.
• File system up to 100TB with EXT4 file-system.
• Very much optimized to support many hardware
• Can control 90000 jobs/min(I believe it’s too good I’m loving it.)
• SELinux sand-boxing for more SELinux control.
• KVM for virtualization.
• 7+3 years of extended support.
• Lower Power consumption(20% less when compared to RHEL5) — A green initiate.
• When handling Virtual machines(VM) RHEL6 on RHEL6 is good at performance when compared to RHEL5 vm on RHEL6 server
• More Reliability, Availability, serviceability(RAS)
• Rapid file system recovery(up to 10x faster than rhel5).
• Resource management through Control group(CGroup) sand-boxing the process.

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Posted in: Update