How to fix RHEL file system

To boot into rescue mode in Red Hat Enterprise Linux (RHEL) 8 and check the file system for corruption, you can follow these steps:

Boot into Rescue Mode

1. Reboot the System:
   Restart your system.

2. Access the Boot Menu:
   During the boot process, press a key (usually Esc, F2, F12, or a similar key, depending on your system) to access the boot menu.

3. Select Rescue Mode:
   If using GRUB bootloader, press e to edit the boot parameters of the default kernel. Use the arrow keys to navigate to the line that starts with linux and append rd.break at the end of the line. Then press Ctrl + X to boot with these parameters.

Check and Fix File System Corruption

1. Remount the Root File System: Once you are in the rescue shell, you will need to remount the root file system in read/write mode:

   mount -o remount,rw /sysroot

1. Change Root into the Sysroot: Change the root to the /sysroot directory:

   chroot /sysroot

1. Check and Repair the File System: Use the fsck command to check and repair the file system. Replace /dev/sdXN with your actual device identifier (e.g., /dev/sda1):

   fsck /dev/sdXN

For example, to check the root partition, you might run:

   fsck -f /dev/sda1

1. Exit and Reboot: After the file system check and repair are complete, exit the chroot environment:

   exit

Remount the file system in read-only mode:

   mount -o remount,ro /

Reboot the system:

   reboot

Alternative Method (Using Rescue Media)

1. Boot from Rescue Media:
   Insert the RHEL 8 installation media and boot from it. Select the Troubleshooting option from the boot menu, then select Rescue a Red Hat Enterprise Linux system.

2. Mount the File System:
   Follow the prompts to mount the file system. The installer will detect your RHEL installation and mount it under /mnt/sysimage.

3. Chroot into the Mounted File System:
   Change root into the mounted file system:
   

   chroot /mnt/sysimage

1. Check and Repair the File System:
   Follow the same steps as above to run fsck and repair the file system.

2. Exit and Reboot:
   Exit the chroot environment and reboot the system:
   

   exit
   reboot

You should be able to boot into rescue mode in RHEL 8 and check and fix any file system corruption.