Linux Boot process parsing

Three: Linux boot process parsing date current system hardware clock Hwclock firmware (between hardware and software) clock----> general system clock and firmware clock is synchronous hwclock--hctosys Synchronous Clock Manual modification system Current time: Date 040617032015.38 (2015-04-06 17:03:38) manually modify firmware time: (man Hwclock can view) hwclock--set--date= "4/6/15 17:06:40" Linux PC server One Cmos/bios parsing: System boot process firmware firmware (Cmos/bios) post power-on self-test and bootloader bootloader (GRUB, viewing in vi/etc/grub.conf) load the kernel- Load kernel kernel (drive hardware)--Start Process init--Read execution profile/etc/inittablinux kernel file: Ls/usr/src/linux (kernel only: 1, drive Referral 2, start inittab process VI/ Etc/inittab) a:linux boot process b:linux Run level c:linux start service Management D:grub Configuration and Application (vi/boot/grub/grub.conf) E: Start failure Analysis and solution case: Single user mode application 1:root password forgot to enter the single user mode to reset the root password, as follows: Boot into the Grub interface, press E to enter edit mode, select Kernel line, press E again, enter L or S in the last line of the new interface, To enter single-user mode. Add: Grub command (function key) E: Edit the current boot menu item C: Enter the command line mode for Grub B: Start the current menu item D: Delete the current line ESC: Return to the Grub boot menu interface and cancel any modifications to the current item: Reboot into the countdown for 5 seconds, Press ESC to enter the grub interface--and then select the edits you want to edit by e--To change the RunLevel: Grub edit> kernel/vmlinuz-2.6.18-194.e15 ro root=label=/rhgb Quiet 1 (Enter save, 1 is run level)---> Press B----You can use this--and change password for the graphical interface: password root But the above method is unsafe: "Set grub plus password" to prevent others from entering. One: The wayThe following (2 ways can be obtained ciphertext): 1: Use the Grub-md5-crypt command to bring your own #grub-md5-cryptpassword:123456&wwefefwes*&%dssdsdsadfag^$ Gtuhtgguu (encrypted password) 2: Use the Md5crypt command in the Grub Interactive command line interface #grubgrub>md5cryptpassword:[email protected]$%sdgr*sdfgs*^ % $DGRG (password after MD5) Two: Copy the ciphertext, put it in the Grub configuration file vi/etc/grub.conf Add a password setting to the title: Password--md5 [email protected]$% s encryption OK, next to enter "single user mode" will enter password Grub repair: When booting into the Grub interface but no menu, only one grub> prompt, solution: Enter the interface press c---> enter the GRUB command State grub>cat/boot /grub/grub.conf (for View parameters) Grub>root (hd0,6) (manual boot, set boot partition) Grub>kernel (hd0,6)/vmlinuz-2.4.15-14 ro root=    label=/3 (Specify the location of the kernel) GRUB>INITRD (hd0,6)/initrd-2.4.18-14.img (image file) grub>boot (The system can boot properly) if the error is not able to enter the single-user mode at all? That is, disc Repair mode! Simulation: Cp/etc/inittab/etc/inittab.bak Backup second: Rm/etc/inittab (this file is the system running and starting some important files, the file deletion is not normal boot) This situation we can not enter the "single-user mode" to do? Use GRUB Repair mode: 1: Put the installation disk into the optical drive, can restart the machine after the Bois, the system light drive to guide. 2: After the installation interface comes out, press "F5" key, that is, the Linux rescue mode can be entered after the boot Linux rescue can enter the sh#

Linux Boot process parsing