Boot Up Issues

1. POST
• BIOS - basic I/O
• checks access to RAM
• checks processors
• scans hardware
• addressings
• plug & play
2. CMOS
• overrides are applied
• boot order
3. Start CPU in real mode
• 1MB of memory
• no memory protection
• like 286 Intel processor -> GRUB starts here at Stage 1
• no features; multi-user mode

Booting

Stage 1 = first 512bytes of MBR (Master Boot Record)

- will reset CPU to 32-bit protected mode

- GRUB Stage 1.5 = file system driver is loade; main diff of LILO

Stage 2 = candy

- GRUB Stage 2 = GUI

-files held in /boot/grub

- /menu.lst

- /grub.conf

- /1.5files

- /backup

grub.conf file

Title=

kernel=

initrd=

root (hd0,0) - this is the disk and slice number for this config, is from BIOS

# grub-install

Kernel Files

1. vmlinuz - compressed gzip

2. system.map - addresses to system calls

3. config - actual configuration of the kernel

4. initrd - holds modules for hardware; 

* Kernel modules in /lib/modules

initrd

-pivot root kernel panic

# modprobe - inserts modules into kernel

-ext3 is ext2 with journaling

# depmod -a

# mkinitrd -f /boot/initrd-`uname -r`.img `uname -r`

init

/etc/inittab

-first uncommented line will be default runlevel

runlevels

chkconfig for each runlevel

Removing and re-enabling journal for ext3

GRUB