1. Linux booting How does it work?

2. First the bootloader The first step is for the bootloader to run BIOS indicates what devices to examine Bootstrap program looks on each of the devices indicated for a boot loader –Lilo –Grub Configuration files for booting in /boot

3. Bootloader Kernel image is in /boot Reconfiguring lilo requires running the lilo command in order to rewrite the boot info. (similarly for grub) Mounts file system

4. Mounting file system /etc/fstab Contains configuration to tell loader how to mount the file systems –What device –What directory to mount to –Type of file system /dev/hdb8 /var ext3 /dev/hdb1 / ext3 defaults 1 1 /dev/hdb8 /var ext3 defaults 1 2 …

5. init (the first process) Executed after mounting file systems Configures itself by /etc/inittab Run level -> which scripts to run at startup # 3 - Full multiuser mode # 4 - unused # 5 - X11 # 6 - reboot (Do NOT set initdefault to this) # id:3:initdefault:

6. First rc script – rc.sysinit Executes some of the scripts in /etc/sysconfig including network –Defines relevant environment variables Lots of other scripts Messages seen during boot process

7. Next rc scripts /etc/rc.d/rc 3 –To run at level 3 Does things like checking for the existence of the run files for that level Invokes the right ones “rc 3” -> run scripts in /etc/rc.d/rc3.d

8. rc3.d scripts K09dm@ S15gpm@ S26ypxfrd@ S56xinetd@ S85numlock@ S92lisa@ K90mysql@ S16ypserv@ S31upsmon@ S60cups@ S85proftpd@ S95kheader@ S08ipvsadm@ S17alsa@ S40atd@ S60nfs@ S89internet@ S99devfsd@ S10network@ S18sound@ S40saslauthd@ S60rwhod@ S90crond@ S99linuxconf@ S11portmap@ S20random@ S55named@ S66yppasswdd@ S90postgresql@ S99local@ S12syslog@ S20xfs@ S55ntpd@ S75keytable@ S90squid@ S99mysql@ S13partmon@ S25netfs@ S55sshd@ S80postfix@ S90webmin@ S14nfslock@ S26apmd@ S56rawdevices@ S85httpd@ S91smb@ lrwxr-xr-x 1 root root 17 Oct 23 2002 S10network ->../init.d/network* All scripts are actually in /etc/rc.d/init.d and linked to these. K is used when killing S is used as a startup script Numerical value says order in which to run Example: S10network says to run /etc/rc.d/init.d/network when starting up the system immediately after launching ipvsadm

9. Example script network … case “$1” in start) … restart) … stop) … /etc/rc.d/init.d/network [root@testmachine] init.d%./network restart Runs the scripts with restart option

10. dmesg Linux version 2.4.19-16mdk (quintela@bi.mandrakesoft.com) (gcc version 3.2 (Mandrake Linux 9.0 3.2-1mdk)) #1 Fri Sep 20 18:15:05 BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 0000000000080000 (usable) BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 0000000005fec000 (usable) BIOS-e820: 0000000005fec000 - 0000000005fef000 (ACPI data) BIOS-e820: 0000000005fef000 - 0000000005fff000 (reserved) BIOS-e820: 0000000005fff000 - 0000000006000000 (ACPI NVS) BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved) BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved) BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved) 95MB LOWMEM available. Advanced speculative caching feature not present On node 0 totalpages: 24556 zone(0): 4096 pages. zone(1): 20460 pages. zone(2): 0 pages. Kernel command line: BOOT_IMAGE=linux ro root=341 quiet devfs=mount Found and enabled local APIC! Initializing CPU#0 Detected 929.225 MHz processor. Console: colour dummy device 80x25 …