System Recovery for Linux

Overview of the system boot process
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1. System Startup process

Power

BIOS (in read-only storage on the motherboard, basic input or output system), hardware detection, activation of hardware

Grub System boot (grub boot divided into two stages)
1) Stage 1 MBR (Master boot record) master boot record 0 tracks on hard disk, one sector, 446 bytes
DD If=/dev/zero Of=/dev/vda bs=446 count=1 can empty MBR, restart
Go to rescue mode, perform chroot/mnt/sysimage switch to real/environment,
and execute Grub2-install/dev/vda

Primary boot partition MRB corrupt

View boot partition

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Turn off SELinux

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Select rescue Mode

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Go to the real directory and install the system boot GRUB2

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Recall the hard drive after installation is complete

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Repair complete, can start normally

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2) Phase 2 Grub File boot phase
Locate the/boot partition
Read/boot/grub2/grub.cfg
File lost, Grub2-mkconfig >/boot/grub2/grub.cfg

Boot file Grub corruption

View/directory partition is Vda3

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To delete a boot file

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Manually enter the boot file after booting

Set root= ' hd0,msdos1 ' root directory

linux16/vmlinuz-3.10.0-327.e17.x86_64 ro root=/dev/vdb3 Kernel file

INITRD16/INITRAMFS-3.10.0-327.E17.X86_64.IMG Boot-up service

Boot boot

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Repairing grub.cfg files with Grub2-mfconfig

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Check the/boot/grub2/grub.cfg boot file after entering the system has been restored repair

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Boot kernel, read-only mount/device
Testing equipment
Initialize the device driver
Enter the system initialization phase
Kernel is missing, the new kernel installation package can be resolved
RPM-IVH kernel-xxxxx.rpm--force

Remove kernel files from boot directory

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Missing kernel file, unable to start

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Loading the optical drive

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Enter rescue mode, enter the rescue system, the real system root directory for/mnt/sysimage

Decomposition of kernel packs within the installation disk

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Copy the decomposed kernel file to/mnt/sysimage/boot and exit after completion

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Kernel repair complete, enter system

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System initialization phase
System initialization phase Load INITRD mirror
Open initialization Process Systemd
Start SELinux
Load Kernel parameters
Initialize the system clock, keyboard, host name
Re-read/write mount/device
Activating RAID,LVM
Activate quotas
Start all services in the multi-user.target.wants
Turn on the Virtual Console
Start graphics
initramfs-' Uname-r '. IMG Lost with: mkinitrd initramfs-' uname-r '. img ' uname-r ' recovery

System initialization INITRD Image corruption

Delete initrd image file initramf-3.10.0-327.x86_64.img

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Unable to enter system after reboot, missing initialize image file

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Reboot the system and load the CDROM installation disk file

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Recovering Initramfs image files

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Hard Drive Boot

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Restore success, enter the system

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System Recovery for Linux